CN101789809B - Signal processing system of air fleet link communication/measurement comprehensive channel system - Google Patents

Abstract

The invention relates to a signal processing system of an air fleet link communication/measurement comprehensive channel system. By the invention, a system framework of a non-spread spectrum transmission digital transmission/spread spectrum distance measurement system can be realized on a DSP (Digital Signal Processor) of a circuit board and an FPGA (Field Programmable Gate Array). The signal processing system retains the advantage of high information transmission rate of a non-spread spectrum system, takes the advantages of convenient distance measurement and antiinterference of a spread spectrum system and comprehensively realizes a non-spread spectrum transmission digital transmission/spread spectrum distance measurement comprehensive system in a single channel through a time division multiplex channel mode. And meanwhile, the invention also provides a signal tracking method of the communication/measurement comprehensive channel system based on a realtime prediction algorithm of carrier wave Doppler shift and solves the signal tracking difficulty of the communication/measurement comprehensive channel system under the high dynamic condition. The method can be widely applied to satellite navigation receivers, distance measurement systems and communication/measurement function comprehensive systems based on a suppressed carrier modulation direct sequence spread spectrum system.

Description

The signal processing system of air fleet link communication/measurement comprehensive channel system

Technical field

The present invention relates to a kind of signal processing system of air fleet link communication/measurement comprehensive channel system, belong to aeronautical data chain, technical field of aerial data chains.

Background technology

Number of communications biography, base line measurement separate physically between traditional aircraft, and equipment is separate uncorrelated mutually.In the following group of planes networking cotasking, the formation member aircraft is unmanned plane even the MAV that more single, simple and compact for structure, the lightweight volume of function ratio is little, energy supply is nervous to a great extent.Therefore, have to begin consider the tasks such as number of communications biography and base line measurement, the measurement of air fleet link relevant parameter, time synchronized are integrated into and finish in the station terminal, preferably unified integrated by the algorithm practical function at single hardware platform, the main enforcement approach of this thought be consider in the air fleet link communication link comprehensive realize that number of communications passes and the air fleet link member node between the processes such as Space Baseline/time reference line measurement, motion state information measurement, time synchronized.

In multiple aircraft formation networking task, no matter the communication on computer cluster net adopts grid type Topological Structure or binary tree structure Topological Structure, professional (as: the remote control command distribution of low-speed communication in the group of planes, data are injected distribution, telemetry is returned, etc. be lower than the data service of 5kbps) and the measurement task (as: Space Baseline between the air fleet link member node/time reference line accurate measurement, carrier phase observation, test the speed between the group of planes member node, time synchronized measurement and control, etc.) all realize based on the spread spectrum communication system, in a group of planes, exist between any two member's nodes of communication link and set up the bi-directional full-duplex asynchronous communication channel, two station terminals send information and do not need the coherent forwarding process to the other side independently of one another, adopt the method for two-way one way pseudo range measurement to utilize the bi-directional asynchronous transmission frame to realize local pseudo range measurement, and in the data link layer frame structure, share pseudorange measurement with the other side.High speed data transfer in the group of planes is professional, can adopt following three kinds of methods:

1. short code spread spectrum.As: 15,31,63 pseudo noise codes, can carry out transmitting behind the direct sequence spread spectrum to the quasi high-speed data of 100kbps～2Mbps, if the spreading rate＜30Mcps behind the spread spectrum then communicate by letter with measure the comprehensive channel system implement identical with the low speed situation, if more than spreading rate＞30Mcps then despread-and-demodulation receiving algorithm design difficulty increase to some extent;

2. the air fleet link spread spectrum is measured/non-spread spectrum number biography Multiplexing Carrier system.The method is based on non-equilibrium QPSK (UQPSK) modulation system, transmit leg is in homophase I branch road modulation low speed spread spectrum communication data, the non-spread spectrum communication data of modulation high speed on the quadrature Q branch road, the recipient carries out demodulation to the I tributary signal and processes, realize air fleet link low-speed communication business and measurement task, to the Q tributary signal carry out that carrier wave recovers and clock recovery after the demodulation high-speed data (can utilize I branch road metrical information, as: Doppler frequency shift is used for auxiliary Q branch road carrier wave and recovers, clock recovery), realize that air fleet link high-speed communication number passes professional, the two separate not interfereing with each other;

3. within a certain period, adopt simple direct sequence spread spectrum pattern to realize air fleet link low-speed communication business and measurement task, adopt non-spread spectrum mode to realize that air fleet link high-speed communication number passes in another section period professional, two process time division multiplexing physical channels, handoff procedure control are injected by remote control command or data by the recipient to be realized.

1. in the kind method, measurement performance by the equivalent noise bandwidth of spread-spectrum pseudo code chip period, carrier-to-noise ratio, integration-removing cycle, receiving element code tracking loop delay lock loop, pseudo-code delay lock loop leading-instant-symbol interval between lagging behind determines that (the first two factor is determined by transmitter unit and channel parameter, rear three factors are determined by the receiving element design), information code speed and spreading code grow up to inverse ratio.This just means that the shorter spreading code of employing do not sacrifice measurement performance simultaneously obtaining the higher rate of information throughput, but spreading gain loses, and must rely on the additive method compensation, as: improve antenna gain, increase transmitting power, etc.

The 2. to plant the method cost performance the highest, is relatively to receive publicity and sure method at present, progressively uses in aircraft tracking and communication system.

The 3. the kind method be a kind of system of very enlightening property, a kind of new method that realizes that in unified channel spread spectrum communication/measurement and high-speed communication number pass is proposed on this basis.

Summary of the invention

The object of the present invention is to provide a kind of signal processing system of air fleet link communication/measurement comprehensive channel system, the digital signal processor DSP on the signal processing circuit of intermediate frequency plate of air fleet link terminating machine and FPGA device are realized whole system structure and algorithm.

The signal processing system of a kind of air fleet link communication/measurement comprehensive channel system of the present invention, for the independence characteristics of group of planes formation task, the air fleet link communication of having constructed multiplexing physical channel when counting biography etc. based on spread spectrum measurement/non-spread spectrum with measure comprehensive channel system and its implementation.Signal processing system of the present invention specifically comprises signal generation module and signal trace module; Concrete technical scheme is as follows:

(1), the signal generation module of air fleet link communication/measurement comprehensive channel system

The present invention draws the thinking of batch (-type) burst spread spectrum communication, construct the comprehensive channel system that a kind of solution realizes that in unified channel spread spectrum range finding and high-speed communication number pass---multipling channel system when spread spectrum measurement/non-spread spectrum is counted biography etc., in the single carrier physical channel, utilize principle of multiplexing when waiting, the low code check spread baseband signal of alternate transmission and the non-spread baseband signal of high code check, the relationship of the two as shown in Figure 1.

The multipling channel system satisfied following character when spread spectrum measurement/non-spread spectrum was counted biography etc.:

(1) spread spectrum measuring section and non-spread spectrum number pass segment sync multiplexing (alternately taking) physical channel, are modulated on the same carrier wave with identical baseband form, and spread spectrum measuring section and non-spread spectrum number pass between the section without seam and gap;

(2) to UTC (the perhaps other times system in the inertial system, as: system when a group of planes is formed into columns net) (the 1s interval of UTC definition) in 1PPS section blanking time of definition, multiplex section (cycle is T=1/F) when physical channel is divided into F grade, the 1st section section edge strictly aligns with 1PPS, and F has determined the metrical information output rating;

(3) in each multiplex section, define two pseudo channels: spreading channel and non-spread spectrum Data Channel, multiplex section when these two channels take each grade of physical channel successively, multiplex section had identical structure and duty ratio when each waited, the r% in multiplex section cycle when spreading channel takies etc., the 1-r% in multiplex section cycle when then non-spread spectrum Data Channel takies etc., the integer multiple relation that the non-spread spectrum Data Channel cycle is the spreading channel cycle in each multiplex section;

(4) the transfer clock homology of spreading channel and non-spread spectrum Data Channel, from the frequency marking of air fleet link communication terminal, non-spread spectrum Data Channel number passes the integer multiple relation that bit rate is spreading channel chip speed, and ratio is P;

(5) the spreading channel inter-sync loads M transmission frame in each multiplex section, loads N data bit in each transmission frame inter-sync, and each data bit period is the spreading code cycle, and the spread spectrum code length is the L position;

(6) body realizes that built in the QPSK modulation system dual mode is arranged: 1. I/Q two branch roads are implemented simultaneously; 2. the I branch road is implemented (BPSK in like manner), the Q branch road is that non-spread spectrum number passes passage;

Transmit leg adopted pure spread spectrum system guiding when (7) this system started, and behind recipient's tracking lock transmit leg was transmitted remote control command or data are injected control mode switch, multiplexing system when changing spread spectrum measurement/non-spread spectrum after transmit leg is confirmed over to and counting biography etc.; When the recipient follows the tracks of losing lock, transmit leg is transmitted remote control command or data injection control mode switch, transmit leg changes pure spread spectrum system over to after confirming;

The whole pattern of multiplexing system and pure spread spectrum system was confirmed when (8) spread spectrum measurement/non-spread spectrum was counted biography etc., handoff procedure is that Two-way Feedback is confirmed and the ACTIVE CONTROL process, the recipient injects by remote control command or data transmit leg according to the tracking lock condition and carries out pattern control, and transmit leg predefined leader label in the transmission frame of spreading channel and non-spread spectrum Data Channel extracts the border that is used for the identification synchronous multiplexing for the recipient.

In the multiplexing system, the air fleet link terminal adopts pseudo-code despreading/demodulation+non-spread spectrum number to pass demodulation combination link, utilizes current information phase mutual designation to obtain higher performance when air fleet link spread spectrum measurement/non-spread spectrum is counted biography etc.

In addition, the apparent Doppler shift that the local frequency marking drift of the relative motion between the group of planes formation member node and node causes will be brought the difficulty of next section spreading channel acquisition and tracking, tracking losing lock even mistake occurs catch.Therefore, the high-acruracy survey of each rank Doppler parameter and calculate extremely importantly to the Doppler frequency shift of next section of accurate forecast spreading channel and is recaptured when directly whether decision can accurately keep tracking lock state or mistake to catch fast.For example: for the multiplexing hop count F=5 of per second, spreading channel duty ratio r%=25%, spread spectrum code length L=1023, spread-spectrum code rate=5.115Mcps, non-spread spectrum number passes bit rate: transmission frame number M=2 in the spread-spectrum code chip speed multiplying power P=20, the spreading channel of each multiplex section, and then non-spread spectrum number passes bit rate=102.3Mbps, the lasting cycle of spreading channel is T=F in the transmission frame length N=125bit, each multiplex section ^-1* r%=50ms, enough for the acquisition and tracking time of general receiving element, if Doppler frequency shift parameter measurement estimated value before existing several times then can obtain faster capture time.Multiplexing system performance and receiving element designing requirement affect very large when therefore, selecting in the suitable multiplexing hop count of per second, spreading channel duty ratio, each multiplex section spreading channel to continue cycle three parameters spread spectrum measurements/non-spread spectrum is counted biography etc.

The spread spectrum communication pattern happens suddenly when multiplexing system was similar to etc. the acquisition and tracking of spread-spectrum signal when the spread spectrum measurements/non-spread spectrum that proposes was in essence counted biography etc., therefore take full advantage of the prior information aided capture and can guarantee that with following the tracks of acquisition probability, losing lock probability and receptivity meet the demands, make it identical with conventional continuous spread spectrum system.Here provide following design principle:

1. the spread spectrum duty ratio r% that measures channel is determined by the ratio of the required bit rate of information data transmission and high-transmission code check, in conjunction with a second interior segments F, determine every section in the lasting cycle T=F of spreading channel ^-1* r%, this cycle must be satisfied receiving element and be finished and catch and change over to thick tracking mode (follow the tracks of residual doppler in ± 250Hz, spread-spectrum code chip snaps to 1/4 chip precision);

2. the duty ratio r% of spread spectrum measurement channel is retrained by number of communications biography mission requirements, segments F determines by measuring output rating in second, the two has certain selection space, need to determine according to measuring both sides' relative motion degree of dynamism, F is too small to cause measuring the output rating deficiency, does not satisfy and measures requirement, excessive will cause every section in spreading channel continue the cycle and shorten, be unfavorable for the acquisition and tracking that continues, need compromise to consider;

3. measure output rating when low in every section spreading channel to continue cycle T longer, be conducive to the parallel Direct Acquisition of frequency domain, measuring output rating, to measure the output F that counts when higher in the per second more, is conducive to follow the tracks of keep.

(2), air fleet link communication/measurement comprehensive channel system the signal trace module

To relative motion between member's aircraft in the group of planes formation, introduce suitable statistical estimate model (for example: maneuvering target tracking " present statistical model or interactive multi-model); adopt the statistical filtering algorithm (for example: kalman filtering; adaptive-filtering; robust filtering; strong tracking filter; and similar filtering algorithm), utilize current Doppler shift measurement value to estimate in real time carrier parameter, comprise: carrier phase, the carrier doppler frequency displacement, 1 rank of Doppler frequency shift/2 order derivatives, the spreading code phase place, the code clock then utilizes carrier wave auxiliary code ring track algorithm to calculate in real time.After spreading channel finishes and enters non-spread spectrum Data Channel, these parameters can be used in real-time recursive prediction carrier parameter and code phase parameter, the recipient can utilize these parameters to calculate in real time the required carrier wave NCO frequency control word of carrier tracking loop open loop control, code NCO clock frequency control word, the real-time estimated value of code phase, control carrier tracking loop and code tracking loop NCO counter epoch, guiding open-loop tracking and forecast enter the front border moment and the carrier doppler frequency thereof that next section spread spectrum is measured channel within the non-spread spectrum Data Channel cycle.Provide three important Parameters Forecasting formula:

(1) the real-time prediction value computing formula of carrier doppler frequency displacement

$f_d\left(t_{k+1}\right)=f_d\left(t_k\right)+{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+{\mathrm{\μ}}_f\mathrm{\Δt}---\left(1\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

In the formula (1): f _d(t _k), Be respectively the carrier doppler frequency displacement at t _k0 rank, 1 rank, 2 order derivatives constantly.Front 4 of formula (1) formula right side is f _d(t) (t ∈ [t _k, t _K+1]) 3 rank can lead continuously composition Taylor expansion (

Be remainder), the 5th μ _fΔ t is f _d(t) (t ∈ [t _k, t _K+1]) 3 rank can lead the residual components outside the composition continuously, these two is the unknown, becomes the model error of forecast calculation formula.

Order: δ f _d(t _k), Be respectively f _d(r _k),

Evaluated error, t then _K+1The prediction error δ f of carrier doppler frequency displacement constantly _d(t _K+1| t _k) be:

$\mathrm{\δ}{f}_d\left(t_{k+1}\right|t_k)=\mathrm{\δ}{f}_d\left(t_k\right)+\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\μ\Δt}---\left(2\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},,{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

(2) the real-time prediction value computing formula of code clock frequency

Because the code phase tracing process relies on code clock control code NCO, adopt carrier wave auxiliary code ring tracking strategy to calculate a yard NCO frequency control word by carrier wave NCO frequency control word, establish: f _Code(t) be code clock frequency (f _CodeBe nominal value), f _RF(t) carrier frequency (f _RFBe nominal value), order: λ is the ratio that code clock (spreading rate) and radio frequency are exported frequency, then:

$\mathrm{\λ}=\frac{f_{\mathrm{code}}}{f_{\mathrm{RF}}}=\frac{f_{\mathrm{code}}\left(t\right)}{f_{\mathrm{RF}}\left(t\right)}---\left(3\right)$

f _RF(t)＝f _RF+f _d(t) (4)

Get according to formula (3), formula (4):

f _code(t)＝λf _RF(t)

＝f _code+λf _d(t) (5)

f _code ⁽ⁿ⁾(t)＝λf _RF ⁽ⁿ⁾(t)

＝λf _d ⁽ⁿ⁾(n＝1，2，3，…，) (6)

In the formula (6): f _Code ⁽ⁿ⁾(t) be the code clock frequency constantly n order derivative of t (n=1,2,3 ...).Get according to formula (1), formula (5):

$f_{\mathrm{code}}\left(t_{k+1}\right)=f_{\mathrm{code}}+\mathrm{\λ}{f}_d\left(t_{k+1}\right)$

$=f_{\mathrm{code}}+\mathrm{\λ}{f}_d\left(t_k\right)+\mathrm{\λ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}---\left(7\right)$

$=f_{\mathrm{code}}\left(t_k\right)+{\stackrel{\·}{f}}_{\mathrm{code}}\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}{\stackrel{\·\·}{f}}_{\mathrm{code}}\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1})$

According to formula (1)～formula (7), obtain t _K+1The prediction error δ f of moment code clock frequency _Code(t _K+1| t _k) be:

$\mathrm{\δ}{f}_{\mathrm{code}}\left(t_{k+1}\right|t_k)=\mathrm{\λ\δ}{f}_d\left(t_k\right)+\mathrm{\λ\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}---\left(8\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

Within the non-spread spectrum Data Channel cycle, predicted value and the generated frequency control word of utilizing formula (1), formula (2) to calculate in real time carrier doppler parameter, code Doppler parameter are used for control carrier wave NCO, code NCO at non-spread spectrum Data Channel operate in open loop state, and this pattern is implemented open-loop tracking based on Parameters Forecasting.Carrier wave NCO and code NCO counter counting output value epoch reach set point (by non-spread spectrum Data Channel cycle decision), then can judge the forward position that has arrived next section spread spectrum measurement channel.In spread spectrum is measured channel cycle, change over to as the initial value of capturing carrier/track loop the closed loop of spread-spectrum signal is followed the tracks of with the counting in the last period in the non-spread spectrum Data Channel cycle predicted value of ending constantly to extrapolate, based on carrier tracking loop automatic frequency tracking (AFC)+phase-locked loop (PLL) and code tracking loop railway digital delay lock loop (DDLL) closed-loop control carrier wave NCO, code NCO work, this pattern is followed the tracks of based on following the tracks of residual error FEEDBACK CONTROL enforcement closed loop.

(3) the real-time prediction value computing formula of code phase

Provide a group of planes form into columns in the relation formula of relative velocity all-order derivative and Doppler frequency shift all-order derivative between the member node:

$v^{\left(n\right)}\left(t\right)=c\frac{{f_d}^{\left(n\right)}\left(t\right)}{f_{\mathrm{RF}}}---\left(9\right)$

By formula (9), consider kinematical theory, obtain:

$d\left(t_{k+1}\right)=d\left(t_k\right)+v\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\stackrel{\·}{v}\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\stackrel{\·\·}{v}\left(t_k\right)\mathrm{\Δ}{t}^3+\frac{1}{12}\stackrel{\·\·\·}{v}\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^4+{\mathrm{\μ}}_v\mathrm{\Δt}---\left(10\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

In the formula (10): d (t _k) be t _kGeometric distance between the moment two airborne antenna phase centers.Front 4 of formula (10) formula right side is v (t) (t ∈ [t _k, t _K+1]) 3 rank can lead continuously composition Taylor expansion (

Be remainder), the 5th μ _vΔ t is v (t) (t ∈ [t _k, t _K+1]) 3 rank can lead the residual components outside the composition continuously, these two is the unknown, becomes the model error of forecast calculation formula.Got by formula (10):

$\mathrm{\τ}\left(t_{k+1}\right)=\mathrm{\τ}\left(t_k\right)+\frac{f_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^3+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt}---\left(11\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

In the formula (11): τ (t _k) be t _kTime wave is the spatial time delay between two member's nodes in a group of planes is formed into columns, τ (t _k)=d (t _k)/c (c is vacuum light speed).

Order: δ τ (t _k) be τ (t _k) evaluated error, t then _K+1Prediction error δ τ (t constantly _K+1| t _k) be:

$\mathrm{\δ\τ}\left(t_{k+1}\right|t_k)=\mathrm{\δ\τ}\left(t_k\right)+\frac{\mathrm{\δ}{f}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^3$

$+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt},(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}])---\left(12\right)$

Definitions phase alignment error is φ _Code(t), have:

${\mathrm{\φ}}_{\mathrm{code}}\left(t\right)=\frac{\mathrm{\δ\τ}\left(t\right)}{T_{\mathrm{code}}}=\mathrm{\δ\τ}\left(t\right)\·f_{\mathrm{code}}---\left(13\right)$

Get t by formula (12), formula (13) _K+1Code phase prediction error constantly is:

${\mathrm{\φ}}_{\mathrm{code}}\left(t_{k+1}\right|t_k)=[\mathrm{\δ\τ}\left(t_k\right)+\frac{\mathrm{\δ}{f}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^3$

$+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt}]\·f_{\mathrm{code}}---\left(14\right)$

$={\mathrm{\φ}}_{\mathrm{code}}\left(t_k\right)+\mathrm{\λ\δ}{f}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^3$

$+\frac{1}{12}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c{T}_{\mathrm{code}}}\mathrm{\Δt},(k=\mathrm{0,1},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

In the formula (14): φ _Code(t _k) be t _kCode phase alignment error constantly.When the non-spread spectrum Data Channel of present segment finishes, code phase prediction error φ _Code(t _K+1| t _k) will become the initial code phase positions alignment error that next section spread spectrum is measured channel.

Therefore, the initial tracking error of carrier frequency, code clock frequency initial tracking error, the initial tracking error of code phase cause by Doppler frequency shift extrapolation prediction error, and factor has:

1. current carrier parameter, code phase parameter measurement error;

2. a group of planes is formed into columns, and the relative motion state changed within the non-spread spectrum Data Channel cycle between the interior member node, caused that Doppler frequency three order derivatives increase, and acceleration is undergone mutation (discontinuous) or can not be led;

3. the performance of the accuracy of statistical estimate model and filtering algorithm causes Doppler frequency shift all-order derivative evaluated error.

Formula (2) has been described the initial tracking error of carrier frequency when entering next section spread spectrum measurement channel, formula (8) has been described the initial tracking error of code clock frequency when entering next section spread spectrum measurement channel, and formula (14) has been described the initial tracking error of spreading code phase place when entering next section spread spectrum measurement channel.

For simplicity, only consider f _d(t) composition can be led in three rank, ignores the Taylor expansion remainder.Order:

$\underset{t}{\sup }\left|{\mathrm{\φ}}_{\mathrm{code}}\left(t\right)\right|={\mathrm{\μ}}_0---\left(16\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{f}_d\left(t\right)\right|={\mathrm{\μ}}_1---\left(17\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t\right)\right|={\mathrm{\μ}}_2---\left(18\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t\right)\right|={\mathrm{\μ}}_3---\left(19\right)$

Measure channel at every section spread spectrum terminal, the spreading code phase tracking error is about 1% of chip width, and the carrier track error is less than 1Hz.Get comparatively abominable evaluated error condition, make in formula (16)～(19): μ ₀=0.01, μ ₁=1Hz, μ ₂=50Hz/s, μ ₃=500Hz/s ²If: code clock f _Code=5.115MHz, f _RF=2250.6MHz (S frequency range), λ=1/440 then, T _s=0.2s utilizes formula (2), formula (14) to calculate: δ f _d(t _K+1| t _k)＜21Hz, φ _Code(t _K+1| t _k)＜0.0142, the carrier doppler prediction error is mainly derived from carrier doppler frequency displacement single order, second dervative evaluated error, and the code phase prediction error is mainly derived from current phase estimator error, carrier tracking loop and code tracking loop still can obtain smaller initial tracking error under more abominable evaluated error condition, almost be to keep lock-out state (particularly code phase tracking).Can think, the carrier parameter evaluated error affects much larger than the code phase forecast precision carrier doppler frequency displacement forecast precision.Therefore, when spread spectrum measurement/non-spread spectrum is counted biography etc. in the multiplexing system, for keeping carrier frequency and code phase open-loop tracking accurately and reliably, must obtain accurately Doppler frequency shift and single order thereof, second dervative estimated value.

Can be in spreading channel front border configuration guidance information, as: information bit repeatedly " 1 " or " 0 " and provide forward protect to the spread spectrum transmission frame with guiding with guarantee the acquisition and tracking success; Front border configures repeated synchronous code with guiding and guarantees that demodulating data follows the tracks of successfully synchronously in non-spread spectrum Data Channel.If the recipient confirms to have lost to catch losing lock, then utilize the pure spreading channel of forward link to send instruction to transmit leg and make return link change the pure spread spectrum communication pattern of appointment over to, until recapture successfully and multiplexing system when instruction is controlled transmit leg back channel and changed spread spectrum measurement/non-spread spectrum over to and count biography etc. again behind the tracking lock.

The signal processing system of a kind of air fleet link communication/measurement comprehensive channel system of the present invention, its advantage and effect are: the inventive method has overcome spread spectrum communication occupied bandwidth on the traditional sense, non-spread spectrum number passes and can't find range and jamproof defective.Method disclosed by the invention can be widely used in satellite navigation receiver, ranging system, the communication/distance measurement function Integrated system based on suppressed carrier modulation direct sequence spread spectrum system.

Description of drawings

Figure 1 shows that the schematic diagram of multipling channel system when air fleet link spread spectrum measurement/non-spread spectrum of the present invention is counted biography etc.

Embodiment

The signal processing system of a kind of air fleet link communication/measurement comprehensive channel system of the present invention, for the independence characteristics of group of planes formation task, the air fleet link communication of having constructed multiplexing physical channel when counting biography etc. based on spread spectrum measurement/non-spread spectrum with measure comprehensive channel system and its implementation.Signal processing system of the present invention specifically comprises signal generation module and signal trace module; Concrete technical scheme is as follows:

(1), the signal generation module of air fleet link communication/measurement comprehensive channel system

The present invention draws the thinking of batch (-type) burst spread spectrum communication, construct the comprehensive channel system that a kind of solution realizes that in unified channel spread spectrum range finding and high-speed communication number pass---multipling channel system when spread spectrum measurement/non-spread spectrum is counted biography etc., in the single carrier physical channel, utilize principle of multiplexing when waiting, the low code check spread baseband signal of alternate transmission and the non-spread baseband signal of high code check, the relationship of the two as shown in Figure 1.

The multipling channel system satisfied following character when spread spectrum measurement/non-spread spectrum was counted biography etc.:

(1) spread spectrum measuring section and non-spread spectrum number pass segment sync multiplexing (alternately taking) physical channel, are modulated on the same carrier wave with identical baseband form, and spread spectrum measuring section and non-spread spectrum number pass between the section without seam and gap;

(2) to UTC (the perhaps other times system in the inertial system, as: system when a group of planes is formed into columns net) (the 1s interval of UTC definition) in 1PPS section blanking time of definition, multiplex section (cycle is T=1/F) when physical channel is divided into F grade, the 1st section section edge strictly aligns with 1PPS, and F has determined the metrical information output rating;

(3) in each multiplex section, define two pseudo channels: spreading channel and non-spread spectrum Data Channel, multiplex section when these two channels take each grade of physical channel successively, multiplex section had identical structure and duty ratio when each waited, the r% in multiplex section cycle when spreading channel takies etc., the 1-r% in multiplex section cycle when then non-spread spectrum Data Channel takies etc., the integer multiple relation that the non-spread spectrum Data Channel cycle is the spreading channel cycle in each multiplex section;

(4) the transfer clock homology of spreading channel and non-spread spectrum Data Channel, from the frequency marking of air fleet link communication terminal, non-spread spectrum Data Channel number passes the integer multiple relation that bit rate is spreading channel chip speed, and ratio is P;

(5) the spreading channel inter-sync loads M transmission frame in each multiplex section, loads N data bit in each transmission frame inter-sync, and each data bit period is the spreading code cycle, and the spread spectrum code length is the L position;

(6) body realizes that built in the QPSK modulation system dual mode is arranged: 1. I/Q two branch roads are implemented simultaneously; 2. the I branch road is implemented (BPSK in like manner), the Q branch road is that non-spread spectrum number passes passage;

Transmit leg adopted pure spread spectrum system guiding when (7) this system started, and behind recipient's tracking lock transmit leg was transmitted remote control command or data are injected control mode switch, multiplexing system when changing spread spectrum measurement/non-spread spectrum after transmit leg is confirmed over to and counting biography etc.; When the recipient follows the tracks of losing lock, transmit leg is transmitted remote control command or data injection control mode switch, transmit leg changes pure spread spectrum system over to after confirming;

The whole pattern of multiplexing system and pure spread spectrum system was confirmed when (8) spread spectrum measurement/non-spread spectrum was counted biography etc., handoff procedure is that Two-way Feedback is confirmed and the ACTIVE CONTROL process, the recipient injects by remote control command or data transmit leg according to the tracking lock condition and carries out pattern control, and transmit leg predefined leader label in the transmission frame of spreading channel and non-spread spectrum Data Channel extracts the border that is used for the identification synchronous multiplexing for the recipient.

In the multiplexing system, the air fleet link terminal adopts pseudo-code despreading/demodulation+non-spread spectrum number to pass demodulation combination link, utilizes current information phase mutual designation to obtain higher performance when air fleet link spread spectrum measurement/non-spread spectrum is counted biography etc.

In addition, the apparent Doppler shift that the local frequency marking drift of the relative motion between the group of planes formation member node and node causes will be brought the difficulty of next section spreading channel acquisition and tracking, tracking losing lock even mistake occurs catch.Therefore, the high-acruracy survey of each rank Doppler parameter and calculate extremely importantly to the Doppler frequency shift of next section of accurate forecast spreading channel and is recaptured when directly whether decision can accurately keep tracking lock state or mistake to catch fast.For example: for the multiplexing hop count F=5 of per second, spreading channel duty ratio r%=25%, spread spectrum code length L=1023, spread-spectrum code rate=5.115Mcps, non-spread spectrum number passes bit rate: transmission frame number M=2 in the spread-spectrum code chip speed multiplying power P=20, the spreading channel of each multiplex section, and then non-spread spectrum number passes bit rate=102.3Mbps, the lasting cycle of spreading channel is T=F in the transmission frame length N=125bit, each multiplex section ^-1* r%=50ms, enough for the acquisition and tracking time of general receiving element, if Doppler frequency shift parameter measurement estimated value before existing several times then can obtain faster capture time.Multiplexing system performance and receiving element designing requirement affect very large when therefore, selecting in the suitable multiplexing hop count of per second, spreading channel duty ratio, each multiplex section spreading channel to continue cycle three parameters spread spectrum measurements/non-spread spectrum is counted biography etc.

The spread spectrum communication pattern happens suddenly when multiplexing system was similar to etc. the acquisition and tracking of spread-spectrum signal when the spread spectrum measurements/non-spread spectrum that proposes was in essence counted biography etc., therefore take full advantage of the prior information aided capture and can guarantee that with following the tracks of acquisition probability, losing lock probability and receptivity meet the demands, make it identical with conventional continuous spread spectrum system.Here provide following design principle:

1. the spread spectrum duty ratio r% that measures channel is determined by the ratio of the required bit rate of information data transmission and high-transmission code check, in conjunction with a second interior segments F, determine every section in the lasting cycle T=F of spreading channel ^-1* r%, this cycle must be satisfied receiving element and be finished and catch and change over to thick tracking mode (follow the tracks of residual doppler in ± 250Hz, spread-spectrum code chip snaps to 1/4 chip precision);

2. the duty ratio r% of spread spectrum measurement channel is retrained by number of communications biography mission requirements, segments F determines by measuring output rating in second, the two has certain selection space, need to determine according to measuring both sides' relative motion degree of dynamism, F is too small to cause measuring the output rating deficiency, does not satisfy and measures requirement, excessive will cause every section in spreading channel continue the cycle and shorten, be unfavorable for the acquisition and tracking that continues, need compromise to consider;

3. measure output rating when low in every section spreading channel to continue cycle T longer, be conducive to the parallel Direct Acquisition of frequency domain, measuring output rating, to measure the output F that counts when higher in the per second more, is conducive to follow the tracks of keep.

(2), air fleet link communication/measurement comprehensive channel system the signal trace module

To relative motion between member's aircraft in the group of planes formation, introduce suitable statistical estimate model (for example: maneuvering target tracking " present statistical model or interactive multi-model); adopt the statistical filtering algorithm (for example: kalman filtering; adaptive-filtering; robust filtering; strong tracking filter; and similar filtering algorithm), utilize current Doppler shift measurement value to estimate in real time carrier parameter, comprise: carrier phase, the carrier doppler frequency displacement, 1 rank of Doppler frequency shift/2 order derivatives, the spreading code phase place, the code clock then utilizes carrier wave auxiliary code ring track algorithm to calculate in real time.After spreading channel finishes and enters non-spread spectrum Data Channel, these parameters can be used in real-time recursive prediction carrier parameter and code phase parameter, the recipient can utilize these parameters to calculate in real time the required carrier wave NCO frequency control word of carrier tracking loop open loop control, code NCO clock frequency control word, the real-time estimated value of code phase, control carrier tracking loop and code tracking loop NCO counter epoch, guiding open-loop tracking and forecast enter the front border moment and the carrier doppler frequency thereof that next section spread spectrum is measured channel within the non-spread spectrum Data Channel cycle.Provide three important Parameters Forecasting formula:

(1) the real-time prediction value computing formula of carrier doppler frequency displacement

$f_d\left(t_{k+1}\right)=f_d\left(t_k\right)+{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+{\mathrm{\μ}}_f\mathrm{\Δt}---\left(1\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

In the formula (1): f _d(t _k),

Be respectively the carrier doppler frequency displacement at t _k0 rank, 1 rank, 2 order derivatives constantly.Front 4 of formula (1) formula right side is f _d(t) (t ∈ [t _k, t _K+1]) 3 rank can lead continuously composition Taylor expansion (

Be remainder), the 5th μ _fΔ t is f _d(t) (t ∈ [t _k, t _K+1]) 3 rank can lead the residual components outside the composition continuously, these two is the unknown, becomes the model error of forecast calculation formula.

Order: δ f _d(t _k),

Be respectively f _d(t _k),

Evaluated error, t then _K+1The prediction error δ f of carrier doppler frequency displacement constantly _d(t _K+1| t _k) be:

$\mathrm{\δ}{f}_d\left(t_{k+1}\right|t_k)=\mathrm{\δ}{f}_d\left(t_k\right)+\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\μ\Δt}---\left(2\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},,{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

(2) the real-time prediction value computing formula of code clock frequency

Because the code phase tracing process relies on code clock control code NCO, adopt carrier wave auxiliary code ring tracking strategy to calculate a yard NCO frequency control word by carrier wave NCO frequency control word, establish: f _Code(t) be code clock frequency (f _CodeBe nominal value), f _RF(t) carrier frequency (f _RFBe nominal value), order: λ is the ratio that code clock (spreading rate) and radio frequency are exported frequency, then:

$\mathrm{\λ}=\frac{f_{\mathrm{code}}}{f_{\mathrm{RF}}}=\frac{f_{\mathrm{code}}\left(t\right)}{f_{\mathrm{RF}}\left(t\right)}---\left(3\right)$

f _RF(t)＝f _RF+f _d(t) (4)

Get according to formula (3), formula (4):

f _code(t)＝λf _RF(t)

＝f _code+λf _d(t) (5)

f _code ⁽ⁿ⁾(t)＝λf _RF ⁽ⁿ⁾(t)

＝λf _d ⁽ⁿ⁾(t)(n＝1，2，3，…，) (6)

In the formula (6): f _Code ⁽ⁿ⁾(t) be the code clock frequency constantly n order derivative of t (n=1,2,3 ...).Get according to formula (1), formula (5):

$f_{\mathrm{code}}\left(t_{k+1}\right)=f_{\mathrm{code}}+\mathrm{\λ}{f}_d\left(t_{k+1}\right)$

$=f_{\mathrm{code}}+\mathrm{\λ}{f}_d\left(t_k\right)+\mathrm{\λ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}---\left(7\right)$

$=f_{\mathrm{code}}\left(t_k\right)+{\stackrel{\·}{f}}_{\mathrm{code}}\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}{\stackrel{\·\·}{f}}_{\mathrm{code}}\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1})$

According to formula (1)～formula (7), obtain t _K+1The prediction error δ f of moment code clock frequency _Code(t _K+1| t _k) be:

$\mathrm{\δ}{f}_{\mathrm{code}}\left(t_{k+1}\right|t_k)=\mathrm{\λ\δ}{f}_d\left(t_k\right)+\mathrm{\λ\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}---\left(8\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

Within the non-spread spectrum Data Channel cycle, predicted value and the generated frequency control word of utilizing formula (1), formula (2) to calculate in real time carrier doppler parameter, code Doppler parameter are used for control carrier wave NCO, code NCO at non-spread spectrum Data Channel operate in open loop state, and this pattern is implemented open-loop tracking based on Parameters Forecasting.Carrier wave NCO and code NCO counter counting output value epoch reach set point (by non-spread spectrum Data Channel cycle decision), then can judge the forward position that has arrived next section spread spectrum measurement channel.In spread spectrum is measured channel cycle, change over to as the initial value of capturing carrier/track loop the closed loop of spread-spectrum signal is followed the tracks of with the counting in the last period in the non-spread spectrum Data Channel cycle predicted value of ending constantly to extrapolate, based on carrier tracking loop automatic frequency tracking (AFC)+phase-locked loop (PLL) and code tracking loop railway digital delay lock loop (DDLL) closed-loop control carrier wave NCO, code NCO work, this pattern is followed the tracks of based on following the tracks of residual error FEEDBACK CONTROL enforcement closed loop.

(3) the real-time prediction value computing formula of code phase

Provide a group of planes form into columns in the relation formula of relative velocity all-order derivative and Doppler frequency shift all-order derivative between the member node:

$v^{\left(n\right)}\left(t\right)=c\frac{{f_d}^{\left(n\right)}\left(t\right)}{f_{\mathrm{RF}}}---\left(9\right)$

By formula (9), consider kinematical theory, obtain:

$d\left(t_{k+1}\right)=d\left(t_k\right)+v\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\stackrel{\·}{v}\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\stackrel{\·\·}{v}\left(t_k\right)\mathrm{\Δ}{t}^3+\frac{1}{12}\stackrel{\·\·\·}{v}\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^4+{\mathrm{\μ}}_v\mathrm{\Δt}---\left(10\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

In the formula (10): d (t _k) be t _kGeometric distance between the moment two airborne antenna phase centers.Front 4 of formula (10) formula right side is v (t) (t ∈ [t _k, t _K+1]) 3 rank can lead continuously composition Taylor expansion (

Be remainder), the 5th μ _vΔ t is v (t) (t ∈ [t _k, t _K+1]) 3 rank can lead the residual components outside the composition continuously, these two is the unknown, becomes the model error of forecast calculation formula.Got by formula (10):

$\mathrm{\τ}\left(t_{k+1}\right)=\mathrm{\τ}\left(t_k\right)+\frac{f_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^3+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt}---\left(11\right)$

$(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

In the formula (11): τ (t _k) be t _kTime wave is the spatial time delay between two member's nodes in a group of planes is formed into columns, τ (t _k)=d (t _k)/c (c is vacuum light speed).

Order: δ τ (t _k) be τ (t _k) evaluated error, t then _K+1Prediction error δ τ (t constantly _K+1| t _k) be:

$\mathrm{\δ\τ}\left(t_{k+1}\right|t_k)=\mathrm{\δ\τ}\left(t_k\right)+\frac{\mathrm{\δ}{f}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^3$

$+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt},(k=\mathrm{0,1,2},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}])---\left(12\right)$

Definitions phase alignment error is φ _Code(t), have:

${\mathrm{\φ}}_{\mathrm{code}}\left(t\right)=\frac{\mathrm{\δ\τ}\left(t\right)}{T_{\mathrm{code}}}=\mathrm{\δ\τ}\left(t\right)\·f_{\mathrm{code}}---\left(13\right)$

Get t by formula (12), formula (13) _K+1Code phase prediction error constantly is:

${\mathrm{\φ}}_{\mathrm{code}}\left(t_{k+1}\right|t_k)=[\mathrm{\δ\τ}\left(t_k\right)+\frac{\mathrm{\δ}{f}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^3$

$+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt}]\·f_{\mathrm{code}}---\left(14\right)$

$={\mathrm{\φ}}_{\mathrm{code}}\left(t_k\right)+\mathrm{\λ\δ}{f}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^3$

$+\frac{1}{12}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c{T}_{\mathrm{code}}}\mathrm{\Δt},(k=\mathrm{0,1},...,N,\mathrm{\Δt}=t_k-t_{k+1},{\mathrm{\ϵ}}_k\∈[t_k,t_{k+1}\left]\right)$

In the formula (14): φ _Code(t _k) be t _kCode phase alignment error constantly.When the non-spread spectrum Data Channel of present segment finishes, code phase prediction error φ _Code(t _K+1| t _k) will become the initial code phase positions alignment error that next section spread spectrum is measured channel.

Therefore, the initial tracking error of carrier frequency, code clock frequency initial tracking error, the initial tracking error of code phase cause by Doppler frequency shift extrapolation prediction error, and factor has:

1. current carrier parameter, code phase parameter measurement error;

2. a group of planes is formed into columns, and the relative motion state changed within the non-spread spectrum Data Channel cycle between the interior member node, caused that Doppler frequency three order derivatives increase, and acceleration is undergone mutation (discontinuous) or can not be led;

3. the performance of the accuracy of statistical estimate model and filtering algorithm causes Doppler frequency shift all-order derivative evaluated error.

Formula (2) has been described the initial tracking error of carrier frequency when entering next section spread spectrum measurement channel, formula (8) has been described the initial tracking error of code clock frequency when entering next section spread spectrum measurement channel, and formula (14) has been described the initial tracking error of spreading code phase place when entering next section spread spectrum measurement channel.

For simplicity, only consider f _d(t) composition can be led in three rank, ignores the Taylor expansion remainder.Order:

$\underset{t}{\sup }\left|{\mathrm{\φ}}_{\mathrm{code}}\left(t\right)\right|={\mathrm{\μ}}_0---\left(16\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{f}_d\left(t\right)\right|={\mathrm{\μ}}_1---\left(17\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t\right)\right|={\mathrm{\μ}}_2---\left(18\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t\right)\right|={\mathrm{\μ}}_3---\left(19\right)$

Measure channel at every section spread spectrum terminal, the spreading code phase tracking error is about 1% of chip width, and the carrier track error is less than 1Hz.Get comparatively abominable evaluated error condition, make in formula (16)～(19): μ ₀=0.01, μ ₁=1Hz, μ ₂=50Hz/s, μ ₃=500Hz/s ²If: code clock f _Code=5.115MHz, f _RF=2250.6MHz (S frequency range), λ=1/440 then, Ts=0.2s utilizes formula (2), formula (14) to calculate: δ f _d(t _K+1| t _k)＜21Hz, φ _Code(t _K+1| t _k)＜0.0142, the carrier doppler prediction error is mainly derived from carrier doppler frequency displacement single order, second dervative evaluated error, and the code phase prediction error is mainly derived from current phase estimator error, carrier tracking loop and code tracking loop still can obtain smaller initial tracking error under more abominable evaluated error condition, almost be to keep lock-out state (particularly code phase tracking).Can think, the carrier parameter evaluated error affects much larger than the code phase forecast precision carrier doppler frequency displacement forecast precision.Therefore, when spread spectrum measurement/non-spread spectrum is counted biography etc. in the multiplexing system, for keeping carrier frequency and code phase open-loop tracking accurately and reliably, must obtain accurately Doppler frequency shift and single order thereof, second dervative estimated value.

Can be in spreading channel front border configuration guidance information, as: information bit repeatedly " 1 " or " 0 " and provide forward protect to the spread spectrum transmission frame with guiding with guarantee the acquisition and tracking success; Front border configures repeated synchronous code with guiding and guarantees that demodulating data follows the tracks of successfully synchronously in non-spread spectrum Data Channel.If the recipient confirms to have lost to catch losing lock, then utilize the pure spreading channel of forward link to send instruction to transmit leg and make return link change the pure spread spectrum communication pattern of appointment over to, until recapture successfully and multiplexing system when instruction is controlled transmit leg back channel and changed spread spectrum measurement/non-spread spectrum over to and count biography etc. again behind the tracking lock.

Claims (1)

1. the signal processing system of an air fleet link communication/measurement comprehensive channel system, independence characteristics for group of planes formation task, the air fleet link communication of having constructed multiplexing physical channel when counting biography etc. based on spread spectrum measurement/non-spread spectrum with measure comprehensive channel system and its implementation, it is characterized in that: this signal processing system specifically comprises signal generation module and signal trace module; Concrete technical scheme is as follows:

(1), the signal generation module of air fleet link communication/measurement comprehensive channel system

This module is the comprehensive channel system that realizes that in unified channel spread spectrum range finding and high-speed communication number pass---multipling channel system when spread spectrum measurement/non-spread spectrum is counted biography etc., in the single carrier physical channel, utilize principle of multiplexing when waiting, the low code check spread baseband signal of alternate transmission and the non-spread baseband signal of high code check;

The multipling channel system satisfied following character when spread spectrum measurement/non-spread spectrum was counted biography etc.:

(1) spread spectrum measuring section and non-spread spectrum number pass the multiplexing physical channel of segment sync, are modulated on the same carrier wave with identical baseband form, and spread spectrum measuring section and non-spread spectrum number pass between the section without seam and gap;

(2) in 1PPS section blanking time to the UTC definition, i.e. the 1s interval of UTC definition, multiplex section when physical channel is divided into F grade, the cycle is T=1/F, and a section edge of the 1st section strictly aligns with 1PPS, and F has determined the metrical information output rating;

(3) when each waits in the multiplex section, define two pseudo channels: spread spectrum is measured channel and non-spread spectrum Data Channel, multiplex section when these two channels take each grade of physical channel successively, multiplex section had identical structure and duty ratio when each waited, the r% in multiplex section cycle when spread spectrum is measured channel occupancy etc., the 1-r% in multiplex section cycle when then non-spread spectrum Data Channel takies etc., the non-spread spectrum Data Channel cycle is the integer multiple relation that spread spectrum is measured channel cycle in the multiplex section when each waits;

(4) spread spectrum is measured the transfer clock homology of channel and non-spread spectrum Data Channel, and from the frequency marking of air fleet link terminal, non-spread spectrum number passes the integer multiple relation that bit rate is spread-spectrum code rate, and ratio is P;

(5) when each waits in the multiplex section spread spectrum measure the channel inter-sync and load M transmission frame, in N data bit of each transmission frame inter-sync loading, each data bit period is the spreading code cycle, the spread spectrum code length is the L position;

(6) body realizes that built in the QPSK modulation system dual mode is arranged: 1. I/Q two branch roads are implemented simultaneously; 2. the I branch road is implemented, the Q branch road is non-spread spectrum Data Channel;

Transmit leg adopted pure spread spectrum system guiding when (7) this system started, and behind recipient's tracking lock transmit leg was transmitted remote control command or data are injected control mode switch, multiplexing system when changing spread spectrum measurement/non-spread spectrum after transmit leg is confirmed over to and counting biography etc.; When the recipient follows the tracks of losing lock, transmit leg is transmitted remote control command or data injection control mode switch, transmit leg changes pure spread spectrum system over to after confirming;

The whole pattern of multiplexing system and pure spread spectrum system was confirmed when (8) spread spectrum measurement/non-spread spectrum was counted biography etc., handoff procedure is that Two-way Feedback is confirmed and the ACTIVE CONTROL process, the recipient injects by remote control command or data transmit leg according to the tracking lock condition and carries out pattern control, and transmit leg predefined leader label in the transmission frame of spread spectrum measurement channel and non-spread spectrum Data Channel extracts the border that is used for the identification synchronous multiplexing for the recipient;

When air fleet link spread spectrum measurement/non-spread spectrum is counted biography etc. in the multiplexing system, the air fleet link terminal adopts pseudo-code despreading/solutions to be in harmonious proportion non-spread spectrum number and passes demodulation combination link, utilizes the higher performance of current information phase mutual designation acquisition;

In addition, the apparent Doppler shift that the local frequency marking drift of the relative motion between the group of planes formation member node and node causes will bring next section spread spectrum to measure the difficulty that channel acquisition is followed the tracks of, and losing lock is followed the tracks of in generation even mistake is caught; Therefore, the Doppler frequency shift that the high-acruracy survey of each rank Doppler parameter and calculating are measured channel to next section of accurate forecast spread spectrum is extremely important, and recapture fast when directly whether decision can accurately keep tracking lock state or mistake to catch: multiplex section during for F etc., F=5, spread spectrum is measured channel duty ratio r%=25%, spread spectrum code length L=1023, spread-spectrum code rate=5.115Mcps, non-spread spectrum number passes bit rate: spread-spectrum code chip speed multiplying power P=20, the spread spectrum of multiplex section was measured transmission frame number M=2 in the channel when each waited, then non-spread spectrum number passes bit rate=102.3Mbps, at the data bit N=125bit that each transmission frame inter-sync loads, the interior spread spectrum measurement of the multiplex section lasting cycle of channel was T=F when each waited ^-1* r%=50ms, enough for the acquisition and tracking time of general receiving element, if Doppler frequency shift parameter measurement estimated value before existing several times then can obtain faster capture time;

The spread spectrum communication pattern happens suddenly when multiplexing system was similar to etc. the acquisition and tracking of spread-spectrum signal when the spread spectrum measurements/non-spread spectrum that proposes was in essence counted biography etc., therefore take full advantage of the prior information aided capture and can guarantee that with following the tracks of acquisition probability, losing lock probability and receptivity meet the demands, make it identical with conventional continuous spread spectrum system; Design principle is as follows:

1. the spread spectrum duty ratio r% that measures channel is determined by the ratio of the required bit rate of information data transmission and high-transmission code check, multiplex section when waiting for F, determine every section in the lasting cycle T=F of spread spectrum measurement channel ^-1* r%, this cycle must be satisfied receiving element and be finished and catch and change over to thick tracking mode---follow the tracks of residual doppler in ± 250Hz, spread-spectrum code chip snaps to 1/4 chip precision;

2. the duty ratio r% of spread spectrum measurement channel is retrained by number of communications biography mission requirements, multiplex section when waiting for F, the F value determines by measuring output rating, the two has certain selection space, needs to determine according to measuring both sides' relative motion degree of dynamism, and F is too small to cause measuring the output rating deficiency, do not satisfy and measure requirement, excessive will cause every section in spread spectrum measure channel and continue the cycle and shorten, be unfavorable for the acquisition and tracking that continues, need compromise to consider;

When 3. measuring output rating each waiting when low in the multiplex section spread spectrum measure channel to continue cycle T longer, be conducive to the parallel Direct Acquisition of frequency domain; The measurement output rating is conducive to when higher follow the tracks of keep;

(2), air fleet link communication/measurement comprehensive channel system the signal trace module

To relative motion between the member node in the group of planes formation, introduce the statistical estimate model, adopt the statistical filtering algorithm, utilize current Doppler shift measurement value to estimate in real time carrier parameter, comprise: 1 rank of carrier phase, carrier doppler frequency displacement, Doppler frequency shift/2 order derivatives, spreading code phase place, the code clock then utilizes carrier wave auxiliary code ring track algorithm to calculate in real time; After spread spectrum is measured the channel end and is entered non-spread spectrum Data Channel, these parameters can be used in real-time recursive prediction carrier parameter and code phase parameter, the recipient utilizes these parameters to calculate in real time the required carrier wave NCO frequency control word of carrier tracking loop open loop control, code NCO clock frequency control word, the real-time estimated value of code phase, control carrier tracking loop and code tracking loop NCO counter epoch, guiding open-loop tracking and forecast enter the front border moment and the carrier doppler frequency thereof that next section spread spectrum is measured channel within the non-spread spectrum Data Channel cycle; Provide following three Parameters Forecasting formula:

1. the real-time prediction value computing formula of carrier doppler frequency displacement

$f_d\left(t_{k+1}\right)=f_d\left(t_k\right)+{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}{\stackrel{\·\·}{f}}_d\left(t_k\right){\mathrm{\Δt}}^2+\frac{1}{6}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right){\mathrm{\Δt}}^3+{\mathrm{\μ}}_f\mathrm{\Δt}$ (1)

Wherein, k=0,1,2 ..., N, Δ t=t _k-t _K+1,ε _k∈ [t _k, t _K+1]

In the formula (1): f _d(t _k), Be respectively the carrier doppler frequency displacement at t _k0 rank, 1 rank, 2 order derivatives constantly; Front 4 of formula (1) formula right side is f _d(t) (t ∈ [t _k, t _K+1]) 3 rank can lead the Taylor expansion of composition continuously, wherein Be remainder, the 5th μ _fΔ t is f _d(t) (t ∈ [t _k, t _K+1]) 3 rank can lead the residual components outside the composition continuously, these two is the unknown, becomes the model error of real-time prediction value computing formula;

Order: δ f _d(t _k),

Be respectively f _d(t _k), Evaluated error, t then _K+1The prediction error δ f of carrier doppler frequency displacement constantly _d(t _K+1| t _k) be:

$\mathrm{\δ}{f}_d\left(t_{k+1}\right|t_k)=\mathrm{\δ}{f}_d\left(t_k\right)+\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right){\mathrm{\Δt}}^2+\frac{1}{6}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right){\mathrm{\Δt}}^3+{\mathrm{\μ}}_f\mathrm{\Δt}$ (2)

Wherein, k=0,1,2 ..., N, Δ t=t _k-t _K+1,, ε _k∈ [t _k, t _K+1]

2. the code clock frequency real-time prediction value computing formula

Because the code phase tracing process relies on code clock control code NCO, adopt carrier wave auxiliary code ring tracking strategy to calculate a yard NCO frequency control word by carrier wave NCO frequency control word, establish: f _Code(t) be the code clock frequency, wherein, f _CodeBe nominal value, f _RF(t) carrier frequency, wherein, f _RFBe nominal value, order: λ is the ratio of code clock and radio frequency output frequency, then:

$\mathrm{\λ}=\frac{f_{\mathrm{code}}}{f_{\mathrm{RF}}}=\frac{f_{\mathrm{code}}\left(t\right)}{f_{\mathrm{RF}}\left(t\right)}---\left(3\right)$

f _RF(t)＝f _RF+f _d(t) (4)

Get according to formula (3), formula (4):

f _code(t)＝λf _RF(t) (5)

＝f _code+λ _fd(t)

f _code ⁽ⁿ⁾(t)＝λf _RF ⁽ⁿ⁾(t) (6)

=λ f _d ⁽ⁿ⁾(t) wherein, n=1,2,3 ...

In the formula (6): f _Code ⁽ⁿ⁾(t) be the code clock frequency at t n order derivative constantly, n=1 wherein, 2,3 ...; Get according to formula (1), formula (5):

$f_{\mathrm{code}}\left(t_{k+1}\right)=f_{\mathrm{code}}+\mathrm{\λ}{f}_d\left(t_{k+1}\right)$

$=f_{\mathrm{code}}+\mathrm{\λ}{f}_d\left(t_k\right)+\mathrm{\λ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}$ (7)

$=f_{\mathrm{code}}\left(t_k\right)+{\stackrel{\·}{f}}_{\mathrm{code}}\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}{\stackrel{\·\·}{f}}_{\mathrm{code}}\left(t_k\right){\mathrm{\Δt}}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}$

Wherein, k=0,1,2 ..., N, Δ t=t _k-t _K+1

According to formula (1)～formula (7), obtain t _K+1The prediction error δ f of moment code clock frequency _Code(t _K+1| t _k) be:

$\mathrm{\δ}{f}_{\mathrm{code}}\left(t_{k+1}\right|t_k)=\mathrm{\λ\ϵ}{f}_d\left(t_k\right)+\mathrm{\λ\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)\mathrm{\Δ}{t}^3+\mathrm{\λ}{\mathrm{\μ}}_f\mathrm{\Δt}$

Wherein, k=0,1,2 ..., N, Δ t=t _k-t _K+1, ε _k∈ [t _k, t _K+1]

Within the non-spread spectrum Data Channel cycle, real-time prediction value, the code real-time prediction value of clock frequency and the generated frequency control word of utilizing formula (1), formula (7) to calculate in real time the carrier doppler frequency displacement is used for control carrier wave NCO, code NCO at non-spread spectrum Data Channel operate in open loop state, and this pattern is implemented open-loop tracking based on Parameters Forecasting; Carrier wave NCO and code NCO counter counting output value epoch reach set point---by non-spread spectrum Data Channel cycle decision, then judge the forward position that has arrived next section spread spectrum measurement channel; In spread spectrum is measured channel cycle, change over to as the initial value of capturing carrier/track loop the closed loop of spread-spectrum signal is followed the tracks of with the counting in the last period in the non-spread spectrum Data Channel cycle predicted value of ending constantly to extrapolate, based on carrier tracking loop automatic frequency tracking and phase-locked loop and code tracking loop railway digital delay lock loop closed-loop control carrier wave NCO, code NCO work, this pattern is implemented closed loop and is followed the tracks of based on following the tracks of the residual error FEEDBACK CONTROL;

3. the real-time prediction value computing formula of code phase

Provide a group of planes form into columns in the relation formula of relative velocity all-order derivative and Doppler frequency shift all-order derivative between the member node:

$v^{\left(n\right)}\left(t\right)=c\frac{{f_d}^{\left(n\right)}\left(t\right)}{f_{\mathrm{RF}}}---\left(9\right)$

By formula (9), consider kinematical theory, obtain:

$d\left(t_{k+1}\right)=d\left(t_k\right)+v\left(v_k\right)\mathrm{\Δt}+\frac{1}{2}\stackrel{\·}{v}\left(t_k\right){\mathrm{\Δt}}^2+\frac{1}{6}\stackrel{\·\·}{v}\left(t_k\right){\mathrm{\Δt}}^2+\frac{1}{6}\stackrel{\·\·}{v}\left(t_k\right){\mathrm{\Δt}}^3+\frac{1}{12}\stackrel{\·\·\·}{v}\left({\mathrm{\ϵ}}_k\right){\mathrm{\Δt}}^4+{\mathrm{\μ}}_v\mathrm{\Δt}$ (10)

Wherein, k=0,1,2 .., N, Δ t=t _k-t _K+1, ε _k∈ [t _k, t _K+1]

In the formula (10): d (t _k) be t _kGeometric distance between the moment two airborne antenna phase centers; Front 4 of formula (10) formula right side is v (t) (t ∈ [t _k, t _K+1]) 3 rank can lead the Taylor expansion of composition continuously, wherein

Be remainder, the 5th μ _vΔ t is v (t) (t ∈ [t _k, t _K+1]) 3 rank can lead the residual components outside the composition continuously, these two is the unknown, becomes the model error of real-time prediction value computing formula; Got by formula (10):

$\mathrm{\τ}\left(t_{k+1}\right)=\mathrm{\τ}\left(t_k\right)+\frac{f_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}{\mathrm{\Δt}}^3+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}{\mathrm{\Δt}}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt}$ (11)

Wherein, k=0,1,2 ..., N, Δ t=t _k-t _K+1, ε _k∈ [t _k, t _K+1]

In the formula (11): τ (t _k) be t _kTime wave is the spatial time delay between two member's nodes in a group of planes is formed into columns, τ (t _k)=d (t _k)/c, wherein, c is vacuum light speed;

Order: δ τ (t _k) be τ (t _k) evaluated error, t then _K+1Prediction error δ τ (t constantly _K+1| t _k) be:

$\mathrm{\δ\τ}\left(t_{k+1}\right|t_k)=\mathrm{\δ\τ}\left(t_k\right)+\frac{\mathrm{\δ}{f}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^3$ (12)

$+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt}$ Wherein, k=0,1,2 ..., N, Δ t=t _k-t _K+1, ε _t∈ [t _k, t _K+1]

Definitions phase alignment error is φ _Code(t), have:

${\mathrm{\φ}}_{\mathrm{code}}\left(t\right)=\frac{\mathrm{\δ\τ}\left(t\right)}{T_{\mathrm{code}}}=\mathrm{\δ\τ}\left(t\right)\·f_{\mathrm{code}}---\left(13\right)$

Get t by formula (12), formula (13) _K+1Code phase prediction error constantly is:

${\mathrm{\φ}}_{\mathrm{code}}\left(t_{k+1}\right|t_k)=[\mathrm{\δ\τ}\left(t_k\right)+\frac{\mathrm{\δ}{f}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δt}+\frac{1}{2}\frac{\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^2+\frac{1}{6}\frac{\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^3$

$+\frac{1}{12}\frac{{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right)}{f_{\mathrm{RF}}}\mathrm{\Δ}{t}^4+\frac{{\mathrm{\μ}}_v}{c}\mathrm{\Δt}]\·f_{\mathrm{code}}---\left(14\right)$

$={\mathrm{\φ}}_{\mathrm{code}}\left(t_k\right)+\mathrm{\λ\δ}{f}_d\left(t_k\right)\mathrm{\Δt}+\frac{1}{2}\mathrm{\λ\δ}{\stackrel{\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^2+\frac{1}{6}\mathrm{\λ\δ}{\stackrel{\·\·}{f}}_d\left(t_k\right)\mathrm{\Δ}{t}^3$

$+\frac{1}{12}\mathrm{\λ}{\stackrel{\·\·\·}{f}}_d\left({\mathrm{\ϵ}}_k\right){\mathrm{\Δt}}^4+\frac{{\mathrm{\μ}}_v}{c{T}_{\mathrm{code}}}\mathrm{\Δt}$ Wherein, k=0,1 ..., N, Δ t=t _k-t _K+1, ε _k∈ [t _k, t _K+1]

In the formula (14): φ _Code(t _k) be t _kCode phase alignment error constantly; When the non-spread spectrum Data Channel of present segment finishes, code phase prediction error φ _Code(t _K+1| t _k) will become the initial code phase positions alignment error that next section spread spectrum is measured channel;

Therefore, the initial tracking error of carrier frequency, code clock frequency initial tracking error, the initial tracking error of code phase cause by Doppler frequency shift extrapolation prediction error, and factor has:

1. current carrier parameter, code phase parameter measurement error;

2. a group of planes is formed into columns, and the relative motion state changed within the non-spread spectrum Data Channel cycle between the interior member node, caused that Doppler frequency three order derivatives increase, and acceleration is undergone mutation or can not be led;

3. the performance of the accuracy of statistical estimate model and filtering algorithm causes Doppler frequency shift all-order derivative evaluated error;

t _K+1The prediction error γ f of carrier doppler frequency displacement constantly _d(t _K+1| t _k) be exactly the initial tracking error of carrier frequency when entering next section spread spectrum measurement channel, t _K+1The prediction error δ f of code clock frequency constantly _Code(t _K+1| t _k) be exactly the initial tracking error of code clock frequency when entering next section spread spectrum measurement channel, t _K+1Code phase prediction error φ constantly _Code(t _K+1| t _k) be exactly the initial tracking error of spreading code phase place when entering next section spread spectrum measurement channel;

For simplicity, only consider f _d(t) composition can be led in three rank, ignores the Taylor expansion remainder; Order:

$\underset{t}{\sup }\left|{\mathrm{\φ}}_{\mathrm{code}}\left(t\right)\right|={\mathrm{\μ}}_0---\left(16\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{f}_d\left(t\right)\right|={\mathrm{\μ}}_1--\left(17\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{\stackrel{\·}{f}}_d\left(t\right)\right|={\mathrm{\μ}}_2---\left(18\right)$

$\underset{t}{\sup }\left|\mathrm{\δ}{\stackrel{\·\·}{f}}_d\left(t\right)\right|={\mathrm{\μ}}_3---\left(19\right)$

Measure channel at every section spread spectrum terminal, the spreading code phase tracking error is about 1% of chip width, and the carrier track error is less than 1Hz; Get comparatively abominable evaluated error condition, make in formula (16)～(19): μ ₀=0.01, μ ₁=1Hz, μ ₂=50Hz/s, μ ₃=500Hz/s ²If: code clock f _Code=5.115MHz, f _RF=2250.6MHz, λ=1/440 then, T _s=0.2s utilizes formula (2), formula (14) to calculate: δ f _d(t _K+1| t _k)＜21Hz, φ _Code(t _K+1| t _k)＜0.0142, the carrier doppler prediction error is mainly derived from carrier doppler frequency displacement single order, second dervative evaluated error, and the code phase prediction error is mainly derived from current phase estimator error, carrier tracking loop and code tracking loop still can obtain smaller initial tracking error under more abominable evaluated error condition, almost be to keep lock-out state; The carrier parameter evaluated error affects much larger than the code phase forecast precision carrier doppler frequency displacement forecast precision; Therefore, when spread spectrum measurement/non-spread spectrum is counted biography etc. in the multiplexing system, for keeping carrier frequency and code phase open-loop tracking accurately and reliably, must obtain accurately Doppler frequency shift and single order thereof, second dervative estimated value;

Front border configuration guidance information in spread spectrum is measured channel, adopt information bit repeatedly " 1 " or " 0 " and provide forward protect to the spread spectrum transmission frame with guiding with guarantee the acquisition and tracking success; Front border configures repeated synchronous code with guiding and guarantees that demodulating data follows the tracks of successfully synchronously in non-spread spectrum Data Channel; If the recipient confirms to have lost to catch losing lock, then utilize the pure spread spectrum of forward link to measure channel and send instruction to transmit leg and make reverse link change the pure spread spectrum communication pattern of appointment over to, until recapture successfully and multiplexing system when instruction is controlled the transmit leg backward channel and changed spread spectrum measurement/non-spread spectrum over to and count biography etc. again behind the tracking lock.

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