CN103916149A - Down-conversion method, down-conversion apparatus, and device with the apparatus - Google Patents
Down-conversion method, down-conversion apparatus, and device with the apparatus Download PDFInfo
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Abstract
The invention relates to a down-conversion method, a down-conversion apparatus, and a device with the apparatus. The method comprises: receiving a digital intermediate frequency signal; obtaining a phase value of a local carrier wave signal; according to the obtained phase value, looking up in a look-up table for a corresponding sine value and a cosine value; and according to the found sine value and the cosine value and the polarity of the digital intermediate frequency signal, determining and outputting the amplitude values of a same-phase signal and an orthogonal signal after down-conversion of the digital intermediate frequency signal. By using the down-conversion method, the down-conversion apparatus, and the device with the apparatus, complex multiplication and addition operation of the digital intermediate frequency signal and a local carrier wave signal is prevented, resources are saved, operation amount is reduced, and signal processing rate is improved.
Description
Technical field
The present invention relates to signal processing technology, relate in particular to a kind of down conversion method, device and the equipment with this device.
Background technology
In GNSS(Global Navigation Satellite System, GPS (Global Position System)) in, antenna reception to satellite-signal after analog down, become intermediate-freuqncy signal.In order this satellite-signal to be caught, is followed the tracks of or extract when pseudo-(extraction of pseudo-random code sequence synchronised clock), need to carry out digital sample with generating digital intermediate-freuqncy signal to this intermediate-freuqncy signal, the digital medium-frequency signal of sampling and local quadrature carrier multiply each other and carry out mixing, realize the carrier wave of this satellite-signal is peeled off to (down-conversion), and generate in-phase signal (I) and orthogonal signalling (Q), this in-phase signal and orthogonal signalling and local pseudo noise code are multiplied each other and can realize despreading.After despreading is processed, can carry out follow-up for example catching, follow the tracks of, the processing such as extraction when pseudo-.
In prior art digital medium-frequency signal is carried out in down-conversion optical mixing process, conventionally by SIN value (sine value) and the COS value (cosine value) of carrier wave NCO output local carrier signal, then corresponding multiplying each other of two paths of signals with intermediate-freuqncy signal by it, in the process multiplying each other, need to carry out a large amount of computings, take more resource, affect the efficiency of signal processing.
Summary of the invention
Provide hereinafter about brief overview of the present invention, to the basic comprehension about some aspect of the present invention is provided.Should be appreciated that this general introduction is not about exhaustive general introduction of the present invention.It is not that intention is determined key of the present invention or pith, and nor is it intended to limit the scope of the present invention.Its object is only that the form of simplifying provides some concept, using this as the preorder in greater detail of discussing after a while.
A main purpose of the present invention is to overcome the defect of prior art, and a kind of down conversion method and device that improves signal treatment effeciency is provided.
Another main purpose of the present invention is to provide a kind of equipment with above-mentioned down-conversion device.
For achieving the above object, the invention provides a kind of down conversion method, comprising:
S1: receive digital medium-frequency signal;
S2: the phase value that obtains local carrier signal;
S3: search corresponding sine value and cosine value according to the phase value obtaining in look-up table;
S4: determine and export in-phase signal after digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling according to the polarity of the sine value of searching and cosine value and digital medium-frequency signal.
For achieving the above object, the present invention also provides a kind of down-conversion device, comprising:
Signal receiving module, for receiving digital medium-frequency signal;
Phase value acquisition module, for obtaining the phase value of local carrier signal;
Search module, for searching corresponding sine value and cosine value according to the phase value obtaining at look-up table;
Processing module, for determining according to the polarity of the sine value searched and cosine value and digital medium-frequency signal and exporting in-phase signal after this digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling.
For achieving the above object, the present invention also provides a kind of equipment, comprises above-mentioned down-conversion device.
Down conversion method of the present invention, device and the equipment with this device, in look-up table, search sine value and cosine value according to the phase value of local carrier signal, and can directly obtain the two paths of signals after down-conversion according to the polarity of the sine value of searching and cosine value and digital medium-frequency signal, avoid digital medium-frequency signal and local carrier signal to carry out complicated multiplication and add operation, saved resource, reduced operand, promoted signal processing speed.
Brief description of the drawings
Below with reference to the accompanying drawings illustrate embodiments of the invention, can understand more easily above and other objects, features and advantages of the present invention.Parts in accompanying drawing are just in order to illustrate principle of the present invention.In the accompanying drawings, same or similar technical characterictic or parts will adopt same or similar Reference numeral to represent.
Fig. 1 is the block diagram of a kind of embodiment of GPS (Global Position System), and this GPS (Global Position System) can comprise down-conversion device of the present invention.
Fig. 2 is the flow chart of a kind of embodiment of down conversion method of the present invention.
Fig. 3 is the block diagram of a kind of embodiment of down-conversion device of the present invention.
Embodiment
Embodiments of the invention are described with reference to the accompanying drawings.The element of describing in an accompanying drawing of the present invention or a kind of execution mode and feature can combine with element and feature shown in one or more other accompanying drawing or execution mode.It should be noted that for purposes of clarity, in accompanying drawing and explanation, omitted expression and the description of unrelated to the invention, parts known to persons of ordinary skill in the art and processing.
The invention provides a kind of down conversion method, comprise the following steps:
S1: receive digital medium-frequency signal;
S2: the phase value that obtains local carrier signal;
S3: search corresponding sine value and cosine value according to the phase value obtaining in look-up table;
S4: determine and export in-phase signal after digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling according to the polarity of the sine value of searching and cosine value and digital medium-frequency signal.
Alternatively, digital medium-frequency signal is 1 bit quantization signal.
Alternatively, in look-up table, store under plane right-angle coordinate sine value and the cosine value of the phase value in any one quadrant at least; In look-up table, search corresponding sine value and cosine value is specially according to the phase value obtaining:
In the time that the phase value obtaining cannot directly find in look-up table, within phase value being transformed to the scope of the phase value of storing in look-up table according to trigonometric function formula, then taking conversion after phase value as address, search corresponding sine value and cosine value;
In the time that the phase value obtaining can directly find in look-up table, taking the phase value that obtains as address, search corresponding sine value and cosine value.
Alternatively, determine and export in-phase signal after digital medium-frequency signal down-conversion and the value of orthogonal signalling according to the polarity of the sine value of searching and cosine value and digital medium-frequency signal, being specially:
Digital medium-frequency signal is described as r=ri+j*rq, and wherein ri is real part, and rq is that imaginary part, j are imaginary unit;
Work as ri=1, when rq=1, the amplitude of in-phase signal and orthogonal signalling is respectively sin θ and cos θ;
Work as ri=1, when rq=-1, the amplitude of in-phase signal and orthogonal signalling be respectively cos θ and-sin θ;
Work as ri=-1, when rq=1, the amplitude of in-phase signal and orthogonal signalling be respectively-cos θ and sin θ;
Work as ri=-1, when rq=-1, be respectively-sin of the amplitude of in-phase signal and orthogonal signalling θ and-cos θ;
Wherein θ is the phase value obtaining.
The present invention also provides a kind of down-conversion device, comprising:
Signal receiving module, for receiving digital medium-frequency signal;
Phase value acquisition module, for obtaining the phase value of local carrier signal;
Search module, for searching corresponding sine value and cosine value according to the phase value obtaining at look-up table;
Processing module, for determining according to the polarity of the sine value searched and cosine value and digital medium-frequency signal and exporting in-phase signal after digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling.
Alternatively, digital medium-frequency signal is 1 bit quantization signal.
Alternatively, in look-up table, store under plane right-angle coordinate sine value and the cosine value of the phase value in any one quadrant at least; Search module for:
In the time that the phase value obtaining cannot directly find in look-up table, within phase value being transformed to the scope of the phase value of storing in look-up table according to trigonometric function formula, then taking conversion after phase value as address, search corresponding sine value and cosine value;
In the time that the phase value obtaining can directly find in look-up table, taking the phase value that obtains as address, search corresponding sine value and cosine value.
Alternatively, digital medium-frequency signal is described as r=ri+j*rq, and wherein ri is real part, and rq is that imaginary part, j are imaginary unit; Processing module is used for:
At ri=1, when rq=1, make the amplitude of in-phase signal and orthogonal signalling be respectively sin θ and cos θ;
At ri=1, when rq=-1, make the amplitude of in-phase signal and orthogonal signalling be respectively cos θ and-sin θ;
At ri=-1, when rq=1, the amplitude of in-phase signal and orthogonal signalling is respectively-cos θ and sin θ;
At ri=-1, when rq=-1, the amplitude of in-phase signal and orthogonal signalling is respectively-sin θ and-cos θ;
Wherein θ is the phase value obtaining.
The present invention also provides a kind of equipment, comprises above-mentioned down-conversion device.
With reference to figure 1, down conversion method of the present invention and device can be applicable to GNSS(GlobalNavigation Satellite System, GPS (Global Position System)) in, this GNSS comprises antenna, radio-frequency module, ADC(Analog-to-Digital Converter, analog to digital converter), baseband module and post-processing module.Antenna is for receiving satellite signal, radio-frequency module to antenna reception to satellite-signal carry out analog down with generate analog if signal, this analog if signal forms digital medium-frequency signal after ADC carries out digitized sampling, this digital medium-frequency signal generates I, Q(homophase and orthogonal after the Digital Down Convert device in baseband module carries out Digital Down Convert) two paths of signals, this I, Q two paths of signals multiply each other and can realize the despreading of signal with local pseudo noise code in baseband module.Signal after despreading can carry out subsequent treatment via post-processing module, for example, catch, follow the tracks of, extract when pseudo-etc.Above-mentioned ADC also can be comparator.
A kind of embodiment of down conversion method of the present invention is for carrying out down-conversion to this digital medium-frequency signal, and it comprises the following steps:
S1: receive digital medium-frequency signal.In this step, can receive the digital medium-frequency signal from ADC or comparator.This digital medium-frequency signal specifically can be described as: r=ri+j*rq, and wherein ri is real number, and rq is imaginary number, and j is imaginary unit.
S2: the phase value that obtains local carrier signal.This step specifically can be by the local carrier signal of detection NCO output to obtain its phase value, and the local quadrature carrier signal producing specifically can be described as s=si+j*sq, and wherein si is real number, and sq is imaginary number, and j is imaginary unit.The phase value obtaining in this step can be between 0-360 degree.
S3: search corresponding sine value and cosine value according to the phase value obtaining in look-up table.
S4: determine and export in-phase signal after digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling according to the polarity of the sine value of searching and cosine value and digital medium-frequency signal.
Particularly, can store sine value and the cosine value of the multiple phase values between 0-360 degree in look-up table,, in the time searching, the phase value that can obtain is that corresponding sine value and cosine value are searched in address in look-up table.
In order to save memory space, also can only be stored in sine value and the cosine value of the phase value at least any quadrant under plane right-angle coordinate, in the time that the phase value obtaining is not in this quadrant, cannot directly in look-up table, search the phase value obtaining, according to trigonometric function formula, the phase value obtaining is transformed to the corresponding phase value of storing in look-up table, and taking the corresponding phase value stored in look-up table as address, search corresponding sine value and cosine value.
For example, in look-up table, can only store in first quartile, i.e. sine value and the cosine value of the phase value between 0 degree-90 degree, that is, only the phase value between 0-90 degree is stored corresponding sine value and cosine value as address.
Suppose that the phase value obtaining is φ 1, the phase value of φ 2 for storing in look-up table, and between φ 1 and φ 2, there is following relation:
When φ 1 is during at the second quadrant, φ 1=180-φ 2, φ 2=180-φ 1;
When φ 1 is during at third quadrant, φ 1=180+ φ 2; φ 2=φ 1-180;
When φ 1 is during in fourth quadrant, φ 1=360-φ 2; φ 2=360-φ 1;
Within can transforming to the scope of the phase value of storing in look-up table according to the phase value of following trigonometric function formula (f1)-(f6) cannot directly find so in look-up table, again taking conversion after phase value as address, search corresponding sine value and cosine value, then determine the positive and negative of its sine value and cosine value according to the phase value obtaining.
sin(π-a)=sina， （f1）；
cos(π-a)=-cosa， （f2）；
sin(π+a)=-sina， （f3）；
cos(π+a)=-cosa， （f4）；
sin（2kπ-α）=-sinα， （f5）；
cos（2kπ-α）=cosα， （f6）。
When φ 1 is during at the second quadrant:
From above formula (f1), sin φ 1=sin(180-φ 2)=sin φ 2, (f1.1)
From above formula (f2), cos φ 1=cos(180-φ 2)=-cos φ 2, (f2.1);
So, when φ 1 is during at the second quadrant, want to obtain sin φ 1 and cos φ 1, can arrive taking φ 2 as address search sin φ 2 and cos φ 2, again according to above formula (f1.1) and (f2.1), the sin φ 2 searching is defined as to sin φ 1, cos φ 2 is overturn and is defined as cos φ 1 for-cos φ 2.
When φ 1 is during at third quadrant:
From above formula (f3), sin φ 1=sin(180+ φ 2)=-sin φ 2, (f3.1);
From above formula (f4), cos φ 1=cos(180+ φ 2)=-cos φ 2, (f4.1);
So, when φ 1 is during at third quadrant, want to obtain sin φ 1 and cos φ 1, can arrive taking φ 2 as address search sin φ 2 and cos φ 2, again according to above formula (f3.1) and (f4.1),, for-sin φ 2 is defined as sin φ 1 the cos φ 2 searching is overturn and is defined as cos φ 1 for-cos φ 2 the sin φ 2 searching as upset.
When φ 1 is during in fourth quadrant:
From above formula (f5), sin φ 1=sin(360-φ 2)=-sin φ 2, (f5.1);
From above formula (f6), cos φ 1=cos(360-φ 2)=cos φ 2, (f6.1);
So, when φ 1 is during in fourth quadrant, want to obtain sin φ 1 and cos φ 1, can arrive taking φ 2 as address search sin φ 2 and cos φ 2, again according to above formula (f5.1) and (f6.1), using the sin φ 2 searching as upset for-sin φ 2 is defined as sin φ 1, the cos φ 2 searching is defined as to cos φ 1.
Therefore, in step S4, while determining the amplitude of I, Q two paths of signals according to the polarity of the sine value of searching and cosine value and digital medium-frequency signal, there are two kinds of situations, be in the time that the phase value obtaining can directly find in look-up table, directly according to the polarity of digital medium-frequency signal, the sine value finding and cosine value carried out after polarity processing (keep polarity constant, will just become and negatively maybe will bear and just become) to the amplitude as I, Q two paths of signals respectively.
Another is, in the time that the phase value obtaining can not directly find in look-up table, need first according to corresponding trigonometric function formula, the sine value of searching and cosine value to be carried out to the first polarity processing, be transformed to sine value and the cosine value of the phase value obtaining, then according to the polarity of digital medium-frequency signal, the sine value under this phase value obtaining and cosine value carried out to the second polarity processing.The first polarity described herein is processed and the sequencing of the second polarity processing is only used to illustrate its principle, when actual enforcement is of the present invention, this first polarity is processed and the second polarity processing can be carried out simultaneously, or, first carry out the second polarity processing, then carry out the first polarity processing.
The polarity of above-mentioned digital medium-frequency signal refers to that the homophase of this digital medium-frequency signal, the value of orthogonal two paths of signals (ri and rq) are for just or for negative.In the present embodiment, this digital medium-frequency signal is 1 bit quantization signal, and its polarity can comprise following four kinds: the first is ri=1, rq=1; The second is ri=1, rq=-1; The third is ri=-1, rq=1; The 4th kind is ri=-1, rq=-1.
In step S4, can determine according to the relation of the amplitude of the polarity of digital medium-frequency signal described below and I, Q two paths of signals the amplitude of I, Q two paths of signals:
Work as ri=1, when rq=1, the value of in-phase signal and orthogonal signalling is respectively sin θ and cos θ; Work as ri=1, when rq=-1, the value of in-phase signal and orthogonal signalling be respectively cos θ and-sin θ; Work as ri=-1, when rq=1, the value of in-phase signal and orthogonal signalling be respectively-cos θ and sin θ; Work as ri=-1, when rq=-1, be respectively-sin of the value of in-phase signal and orthogonal signalling θ and-cos θ, wherein θ is the phase value obtaining.
Below by further step S4 being described for example:
For example, suppose the phase value stored in look-up table between 90-180 degree, the phase value θ 1 that obtains is also at 90-180 degree, and sine value and cosine value corresponding with θ 1 in look-up table are respectively A4 and B4, can in look-up table, find sine value A4 and cosine value B4.Now if the two paths of signals of digital medium-frequency signal (being made as respectively ri and rq) were+1, keep the polarity constant (being just) of sine value A4 and cosine value B4, and A4 and B4 be defined as respectively to I(in-phase signal), Q(orthogonal signalling) amplitude of two paths of signals; If ri is+1, rq is-1, keep cosine value B4 polarity constant, the polarity of sine value A4 is become negative, be respectively-A4 of amplitude and the B4 of I, Q two paths of signals.
Suppose that the phase value θ 2 obtaining is at first quartile, in look-up table, store the phase value θ 3 of a third quadrant and the phase value θ 4 of a fourth quadrant, and there is following relation between θ 2 and θ 3 and θ 2 and θ 4: θ 2=θ 3-180, θ 2=360-θ 4.Can θ 3 be address search sin θ 3 and cos θ 3, and the polarity of the sin θ 2, the cos θ 2 that obtain according to the relation between θ 2 and sine value, the cosine value of θ 3 and digital medium-frequency signal be determined the amplitude of I, Q two paths of signals; Or taking θ 4 as address search sin θ 4 and cos θ 4, and the polarity of the sin θ 2, the cos θ 2 that obtain according to the relation between θ 2 and sine value, the cosine value of θ 4 and digital medium-frequency signal is determined the amplitude of I, Q two paths of signals.For example:
Sin θ 2=-sin θ 3, cos θ 2=-cos θ 3, when ri is that+1, rq is-1 o'clock, the amplitude of in-phase signal is-cos θ 2=cos θ 3 that the amplitude of orthogonal signalling is-sin θ 2=sin θ 3.
Sin θ 2=-sin θ 4, cos θ 2=cos θ 4, when ri is that-1, rq is 1 o'clock, the amplitude of in-phase signal is-cos θ 2=-cos θ 4 that the amplitude of orthogonal signalling is sin θ 2=-sin θ 4.
Relation between sine value under the amplitude of this I, Q two paths of signals and the phase place of obtaining and the polarity of cosine value and digital medium-frequency signal obtains by following inference:
If the signal that this digital medium-frequency signal is carried out after down-conversion is:
dem=r*s=(ri+j*rq)*(si+j*sq) （1）
Making the signal after Digital Down Convert is dem=demi+j*demq, and wherein demi is real number, in order to describe, digital medium-frequency signal is carried out to the in-phase signal obtaining after down-conversion; Demq is imaginary number, in order to describe, digital medium-frequency signal is carried out to the orthogonal signalling that obtain after down-conversion; J is imaginary unit.:
demi＝ri*si-rq*sq
demq＝ri*sq+rq*si （2）
Make si=Sin[φ], sq=Cos[φ], wherein φ is arbitrary phase value, has
demi＝ri*Sin[φ]-rq*Cos[φ]
demq＝ri*Cos[φ]+rq*Sin[φ] （3）
Work as ri=1, when rq=1,
Work as ri=1, when rq=-1,
Work as ri=-1, when rq=1,
Work as ri=-1, when rq=-1,
Make φ=θ+π/4, wherein θ is the phase value obtaining.Make amplitude simultaneously divided by
:
Work as ri=1, when rq=1
demi＝Sinθ （8）
demq＝Cosθ
Work as ri=1, when rq=-1
demi＝Cosθ （9）
demq＝-Sinθ
Work as ri=-1, when rq=1
demi＝-Cosθ （10）
demq＝Sinθ
Work as ri=-1, when rq=-1
demi＝-Sinθ （11）
demq＝-Cosθ
From above formula (8)-(11), work as ri=1, when rq=1, the value of in-phase signal and orthogonal signalling is respectively sin θ and cos θ; Work as ri=1, when rq=-1, the value of in-phase signal and orthogonal signalling be respectively cos θ and-sin θ; Work as ri=-1, when rq=1, the value of in-phase signal and orthogonal signalling be respectively-cos θ and sin θ; Work as ri=-1, when rq=-1, be respectively-sin of the value of in-phase signal and orthogonal signalling θ and-cos θ.
With reference to figure 3, a kind of embodiment of down-conversion device of the present invention comprises: signal receiving module 10, phase place acquisition module 20, search module 30 and processing module 40.
Signal receiving module 10 is for receiving the digital medium-frequency signal that for example ADC produces.
Phase place receiver module 20 is for obtaining the phase value of local carrier signal, and particularly, it is phase-accumulated and produce that the phase value of this local carrier signal can carry out from 0 degree via NCO, and phase place receiver module 20 receives the phase value between 0-360 degree.
Search module 30 for searching corresponding sine value and cosine value according to the phase value obtaining at look-up table, phase value between wherein can 0-360 in look-up table is that corresponding sine value and cosine value are stored in address, also can plane coordinate system under at least the phase value in any one quadrant be that corresponding sine value and cosine value are stored in address.
Processing module 40 is for determining according to the polarity of the sine value searched and cosine value and digital medium-frequency signal and exporting in-phase signal after digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling (I, Q two paths of signals).
Wherein processing module 40 can be determined according to the relation of the amplitude of the polarity of the sine value/cosine value of the above-mentioned phase value of searching, digital medium-frequency signal and I, Q two paths of signals the amplitude of I, Q two paths of signals.
In the time that the phase value obtaining cannot directly find in look-up table, within phase value being transformed to the scope of the phase value of storing in look-up table according to trigonometric function formula, again taking conversion after phase value as address, search corresponding sine value and cosine value, determine the positive and negative of its sine value and cosine value according to the phase value that obtains again, then determine the amplitude of I, Q two paths of signals according to the sine value of the polarity of digital medium-frequency signal and the phase value that obtains and cosine value.
In the time that the phase value obtaining can directly find in look-up table, taking the phase value that obtains as address, search corresponding sine value and cosine value.Determine again the amplitude of I, Q two paths of signals according to the sine value of the polarity of digital medium-frequency signal and the phase value that obtains and cosine value.
Equipment of the present invention can comprise above-mentioned down-conversion device, and equipment of the present invention can be, for example, for carry out the equipment of signal processing at GNSS.
Down conversion method of the present invention and device are searched sine value and cosine value according to the phase value of local carrier signal in look-up table, and can directly obtain the two paths of signals after down-conversion according to the polarity of the sine value of searching and cosine value and digital medium-frequency signal, avoid digital medium-frequency signal and local carrier signal to carry out complicated multiplication and add operation, saved resource, reduced operand, promoted signal processing speed.
Further, by only arbitrarily the phase value in quadrant store corresponding sine value and cosine value as address, and the symmetric relation in quadrant is determined the corresponding sine value of phase value and the cosine value outside this quadrant by each phase value, the amplitude of in-phase signal and orthogonal signalling can either be determined fast, storage resources can also be saved.
Further, making digital intermediate frequency is 1 bit quantization signal, is keeping noise less in the situation that, also further simplified operation, lifting signal treatment effeciency.
In the system and method for the present invention, obviously, each parts or each step reconfigure after can decomposing, combine and/or decomposing.These decomposition and/or reconfigure and should be considered as equivalents of the present invention.Simultaneously, in the above in the description of the specific embodiment of the invention, describe and/or the feature that illustrates can be used in same or similar mode in one or more other execution mode for a kind of execution mode, combined with the feature in other execution mode, or substitute the feature in other execution mode.
Should emphasize, term " comprises/comprises " existence that refers to feature, key element, step or assembly while use herein, but does not get rid of the existence of one or more further feature, key element, step or assembly or add.
Although described the present invention and advantage thereof in detail, be to be understood that in the case of not exceeding the spirit and scope of the present invention that limited by appended claim and can carry out various changes, alternative and conversion.And scope of the present invention is not limited only to the specific embodiment of the described process of specification, equipment, means, method and step.One of ordinary skilled in the art will readily appreciate that from disclosure of the present invention, can use carry out with the essentially identical function of corresponding embodiment described herein or obtain process, equipment, means, method or step result essentially identical with it, that existing and will be developed future according to the present invention.Therefore, appended claim is intended to comprise such process, equipment, means, method or step in their scope.
Claims (9)
1. a down conversion method, is characterized in that, comprises the following steps:
S1: receive digital medium-frequency signal;
S2: the phase value that obtains local carrier signal;
S3: search corresponding sine value and cosine value according to the phase value obtaining in look-up table;
S4: determine and export in-phase signal after described digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling according to the polarity of the sine value of searching and cosine value and described digital medium-frequency signal.
2. down conversion method according to claim 1, is characterized in that, described digital medium-frequency signal is 1 bit quantization signal.
3. down conversion method according to claim 1 and 2, is characterized in that, stores under plane right-angle coordinate sine value and the cosine value of the phase value in any one quadrant at least in described look-up table; In look-up table, search corresponding sine value and cosine value is specially according to the phase value obtaining:
In the time that the phase value obtaining cannot directly find in described look-up table, within described phase value being transformed to the scope of the phase value of storing in described look-up table according to trigonometric function formula, again taking conversion after phase value as address, search corresponding sine value and cosine value;
In the time that the phase value obtaining can directly find in described look-up table, taking the phase value that obtains as address, search corresponding sine value and cosine value.
4. down conversion method according to claim 2, it is characterized in that, determine and export in-phase signal after described digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling according to the polarity of the sine value of searching and cosine value and described digital medium-frequency signal, being specially:
Described digital medium-frequency signal is described as r=ri+j*rq, and wherein ri is real part, and rq is that imaginary part, j are imaginary unit;
Work as ri=1, when rq=1, the amplitude of described in-phase signal and orthogonal signalling is respectively sin θ and cos θ;
Work as ri=1, when rq=-1, the amplitude of described in-phase signal and orthogonal signalling be respectively cos θ and-sin θ;
Work as ri=-1, when rq=1, the amplitude of described in-phase signal and orthogonal signalling be respectively-cos θ and sin θ;
Work as ri=-1, when rq=-1, be respectively-sin of the amplitude of described in-phase signal and orthogonal signalling θ and-cos θ;
Wherein θ is the phase value obtaining.
5. a down-conversion device, is characterized in that, comprising:
Signal receiving module, for receiving digital medium-frequency signal;
Phase value acquisition module, for obtaining the phase value of local carrier signal;
Search module, for searching corresponding sine value and cosine value according to the phase value obtaining at look-up table;
Processing module, for determining according to the polarity of the sine value searched and cosine value and described digital medium-frequency signal and exporting in-phase signal after described digital medium-frequency signal down-conversion and the amplitude of orthogonal signalling.
6. down-conversion device according to claim 5, is characterized in that, described digital medium-frequency signal is 1 bit quantization signal.
7. according to the down-conversion device described in claim 5 or 6, it is characterized in that, in described look-up table, store under plane right-angle coordinate sine value and the cosine value of the phase value in any one quadrant at least; Described search module for:
In the time that the phase value obtaining cannot directly find in described look-up table, within described phase value being transformed to the scope of the phase value of storing in described look-up table according to trigonometric function formula, again taking conversion after phase value as address, search corresponding sine value and cosine value;
In the time that the phase value obtaining can directly find in described look-up table, taking the phase value that obtains as address, search corresponding sine value and cosine value.
8. down-conversion device according to claim 6, is characterized in that, described digital medium-frequency signal is described as r=ri+j*rq, and wherein ri is real part, and rq is that imaginary part, j are imaginary unit; Described processing module is used for:
At ri=1, when rq=1, make the amplitude of described in-phase signal and orthogonal signalling be respectively sin θ and cos θ;
At ri=1, when rq=-1, make the amplitude of described in-phase signal and orthogonal signalling be respectively cos θ and-sin θ;
At ri=-1, when rq=1, the amplitude of described in-phase signal and orthogonal signalling is respectively-cos θ and sin θ;
At ri=-1, when rq=-1, the amplitude of described in-phase signal and orthogonal signalling is respectively-sin θ and-cos θ;
Wherein θ is the phase value obtaining.
9. an equipment, is characterized in that, comprises the down-conversion device described in any one in claim 5-8.
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