EP0314931A2

EP0314931A2 - Method and apparatus for transmitting a plurality of control signals in antenna systems

Info

Publication number: EP0314931A2
Application number: EP88116534A
Authority: EP
Inventors: Raffaello Ing. Pini
Original assignee: BRIONVEGA SpA
Current assignee: BRIONVEGA SpA
Priority date: 1987-11-02
Filing date: 1988-10-06
Publication date: 1989-05-10
Also published as: IT8722478A0; IT1223038B; EP0314931A3

Abstract

Method and apparatus for transmitting a plurality of control signals to an antenna system, in particular for directly receiving television signals from satellites, by means of the radio frequency transmission cables (16) of the system. The apparatus comprises at least one receiving antenna (1,5) having actuators, a low noise converter/amplifier (4, 7), a transmission cable (16), at least one internal unit (21,22), first circuit means (100) for transmitting codified signals in said cable and second circuit means (200) for receiving and decoding those codified signals, for sending adapted electric signals for operating said actuators. For generating receiving and decoding those signals, integrated circuit are used of the type currently employed in remote controls for TV sets, electric gates and similar devices.

Description

The present invention relates to an apparatus (and method) for trasmitting multiple control signals to an antenna, and in particular, but not exclusively, to an apparatus for transmitting adapted electrical signals for operating actuators associated to at least one receiving antenna in an apparatus for receiving direct TV signal from a satellite.
According to the known art, such an apparatus usually consists of a parabolic antenna and of a low noise converter, located inside the building, and its output signal, converted in the range between 950 and 1750 MHz and comprising multiple TV signals, is sent to an internal unit, located inside the building, and proximate, or inside, a television set, by means of a coaxial cable.
The external unit is usually powered through the cable that transmits the radio frequency signals.
For a better signal quality and in particular in view of future services with improved systems, it is preferable to transmit the first medium frequency signal, i.e. in the range of 950-1750 MHz, directly to the user, because possible frequency conversion in the VHF/UHF range will lead to unacceptable signal degrading in the future.
Unfortunately transmitting a signal of such a high frequency entails the use of cables having a larger section than those used for the VHF/UHF range.
Bearing in mind that, to avoid interferences, in satellite transmission adjacent channels have different polarization, i.e. leftsided and rightsided, or vertical and horizontal, two different transmission cables would be necessary to transmit signals of both polarization to the user, and this would entail practical difficulties in making the equipment.
It is known to overcome the inconvenience of using two different cables to convey differently polarized signals, by using parabolic antennas having a polarization shifting device known as "polarotor".
In this case just one transmitting cable can be used but it is necessary to provide a further cable to control the "polarotor" device.
Thinking of the number of satellites that will be transmitting in the future, other istances may arise such as the ability of receiving satellites having different orbital location on the equatorial plane.
In this case, if the working frequency of each satellite is in the same range, one antenna can be used as far as it has a polar mounting and an adapted rotating mechanism.
It is apparent that, in addition to the radio frequency transmitting cable, it is necessary to provide a further control cable, usually a five lead cable, to control the rotating mechanism.
A further case would be that of satellites having different orbital positions and different frequency ranges; in this case it is necessary to use two different antennas because, besides a different laying, they require two distinct signal conversion units.
Instead of having two distinct transmission cables it may be convenient to provide a switch device located at the antennas and a single transmission cable; in this case it is necessary to provide a further multiple lead control cable for the switch device.
Aim of the present invention is that of providing a method and apparatus for transmitting a plurality of control signals to devices located at the antennas that does not require any additional transmission cables.
A further aim of the present invention is that of providing a method, for transmitting a plurality of control signals to devices located at the antennas, that is simple, efficient, easy for the user and economic.
These aims are achieved in an antenna assembly as described above by a method according to claim 1 and by an apparatus according to claim 8.
Improvements and developments of the invention are outlined by the other claims.
Owing to the fact that the control signals are applied as frequency modulation on a carrier of lower frequency, such that does not interfere with the received working signal, and that such modulated frequency signal is respectively fed to the connecting means and picked up from the same means by means of mutually decoupling means, it is possible to utilize as connecting means a single cable connected to the at least one antenna and to the at least one internal receiving unit.
Furthermore, thanks to the fact that the control signals applied as a frequency modulation are codified signals, preferably with a digital code, a plurality of commands can be transmitted through a single transmission means, and for that purpose it is possible to use integrated circuits, usually employed in ordinary remote controls in TV sets, automatic gates and similar devices, easily procured on the market as low priced mass products, thus achieving the proposed aims in a simple and effective way.
Further scopes and advantages of the invention will be apparent by the following detailed description and by the enclosed drawing, provided esclusively as an explicative and not limitative example, in which the single figure schematically shows an antenna system for a direct reception of satellite TV signals, according to the invention.
The system , object of the present invention, aims at transmitting the direct voltage for powering the external unit and a low frequency carrier on the cable transmitting the radio frequency signal, for the short time necessary for the command.
The low frequency carrier is digitally codified by means of pulses and allows to control a plurality of functions, for each distinct code, in any selected point of the apparatus such as, for example, the "polarotor" control, the antenna rotation, the antennas switching, etc.
Each code is constituted by a word containing a number of "bits" and the binary information may, for example, be determined by the time distance of subsequent impulses.
Though several technical solutions are possible to generate, codify and decodify these control signals, a preferred solution of the present invention provides the use of devices (integrated circuits) currently employed in the remote controls of domestic TV sets.
Such per se known devices are employed, in the example described in the present invention, not to send infrared or supersonant signals, but just in order to generate and receive codified signals inserted, by means of adapted filters, on the high frequency cable connecting the antenna systems to the internal receiving unit for the satellite signals.
Several models of different makes are available for such devices and they are all suited for the present invention by modifying the circuits.
More details on the subject are contained in the patent application: "Method and apparatus for transmitting control signals to actuators in television satellite receivers",filed on this same date by the same applicant.
For technical features, reference can be made to each manufacturer's manuals; here common features will be pointed out for such devices which have, for example, a carrier of 38 KHz which can be modulated by a plurality of distanct codes with the P.C.M. system (Pulse Code Modulation).
There are about thirty such codes in the simplest systems and more in highly-developed ones.
In general some of these codes are devoted to switching functions (on, off, band switch) while other codes are devoted to analogical functions (tuning, etc.), i.e. they provide a tension ramp with a resolution of at least 13 bits.
In our instance the switch controls can be suitably used to control the "polarotor" or to switch the antennas, while the high resolution (tension ramp) can be used to rotate the parabola with a high precision aim.
It will be furthermore noted that the different switch and positioning functions can be memorized in at least sixteen memory cells coupled to the so called program push-buttons in order to be recalled subsequently by simply depressing one push-button.
In conclusion, the number of codes, and hence of distinct available control signals, may be greater than the number now actually needed, but the extreme manufacturing semplicity and the low cost of such devices, which are mass-produced, make their choice fully justifiable.
With reference to the figure, which schematically represents an antenna system for directly receiving TV signals from satellites, according to the invention, the parabolic antenna 1 has a polar mounting, a "polarotor" device 3 for switching polarization and a low noise converter/amplifier 4.
Similarly, the parabolic antenna 5 has a "polarotor" device 6 for switching polarization,and a low noise converter/amplifier 7.
The interface decoder unit 200 has the following units: unit 8 is an high-pass filter that allows signals in the range of 950-1750 MHz to pass practically without loss, while the low frequency control signal coming from the decoder 24 of unit 100 is derived through the radio frequency block coil 9 and carried, through the condenser 10, to the decoder device 11.
Coil 32 has such a reactance as to block the low frequency control signal directed to the antennas, while, together with the radio frequency block coils 13, can close the direct current circuit and hence carry the power voltage to the converter/amplifiers of the parabolic antennas and, in case, also to the decoder unit 200.
The signals decoded by unit 11 are carried to the interface circuits 12 to operate the actuators such as, for example, switch 29 which, according to the command decoded by unit 11, allows to carry the radio frequency signal coming from the antenna 1 through cable 14, or the signal coming from the antenna 5 through cable 15, on the single transmission cable 16.
The interface circuit 12 is connected to the rotating device 2 of antenna 1 by means of cable 17, to the "polarotor" device 3 of antenna 1 by means of cable 18 and to the "polarotor" device 6 of antenna 5 by means of cable 19.
According to the codes decoded by unit 11 we will have the rotation in either directions of antenna 1, the switching of polarization of antenna 1 or the switching of polarization of antenna 5.
Inside unit 100 there is a high-pass filter 20 that allows the radio frequency signal in the range of 950-1750 MHz to pass without any detectable loss; this signal comes from the antenna through cable 16 and is sent to the internal unit 21, for receiving the satellite signal, whose output is connected to the TV set 22.
The matrix push-button panel 23 (provided on a remote control for example) has a number of push-buttons, or keys, each corresponding to a desired control function such as for example: left or right rotation of the antenna, switching between antennas, "polarotor" operation, etc.
By depressing one of the push-buttons the codifier circuit 24 generates a carrier modulated by the corresponding digital code, for as long as the push-button is depressed.
Through the condenser 25 and the radio frequency signals block coil 26, such signal is transmitted to cable 16 where it is taken by unit B, by means of coil 9 and condenser 10, decoded by unit 11 and sent to the interface 12 which activate the corresponding actuator.
Coil 27 of unit 100 has such a reactance as to block the low frequency control signals directed towards receiver 21 and together with the radio frequency block coil 28, closes the direct current circuit and transmit power to unit 100.
In conclusion, thanks to the provided filters, the radio frequency working signal is completely transmitted from the amplifier/converter 4 of antenna 1 or from the amplifier/converter 7 of antenna 5 to the internal unit 21, while the low frequency signal is transmitted exclusively on the section of cable 16 comprised between units 100 and 200 for just the short time required to perform the command.
In the described diagram, the satellite receiver 21 powers the entire system but, naturally, power may also be supplied by either unit 100 or unit 200.
Besides the described function control push-buttons, panel 23 may also be provided with a memory push-button and further push-buttons in order to memorize several satellite aiming positions of the antenna, one for each push-button, to be recalled automatically depressing the corresponding button.
Such feature does not require any further circuit complication, being already provided on the available devices.
In the practical realization, the codifier circuit 24 (based, for example, on the M708 integrated circuit available on the market) and the decoder 11 (based, for example, on the integrated circuit M490) will be made according to the specifications provided by the manufacturer of the selected devices (in this case "S.G.S"), while the interface circuit 12 will be made according to the type of actuators selected.
In particular, switch 29 may be of a fully electronic type, for example as those currently used for the inlets switching in the internal units for receiving satellite signals.
The operations of the described system is apparent from the above description and enclosed drawings.
From the above description are also apparent the advantages of the system according to the present invention.
In particular, a great advantage resides in the fact that all signals, control signals and working signals, are transmitted through the single radio frequency transmission cable, preferably a coaxial cable, thus greatly simplifying the apparatus especially in the case of communal receiving apparatuses having a plurality of receivers.
Furthermore the ability to memorize the more frequently occurring situations is of great convenience to the user.
Naturally numerous variations can be made, besides those described, by the man of the art on the described apparatus without departing from the scope of the present invention.

Claims

1. Method for transmitting a plurality of control signals in antenna systems, particularly for directly receiving television signals from satellites, such systems comprising at least one receiving antenna (1, 5) having mechanical actuators and connection means connecting said at least one antenna to at least one internal unit for receiving signals from satellites, characterized in that it comprises the steps of:

a) generating a low frequency carrier for the short time necessary to perform the command, said carrier having a frequency lower than the lowest frequency of the working signal received by said antenna;

b) generating a control signal corresponding to the command to be given to the antenna systems;

c) codifying the control signal by means of codifying means (24) according to a plurality of codes respectively corresponding to each command;

d) modulating said low frequency carrier with the codified control signal and applying said carrier to an end (30), of said connection means (16), connected to a receiving internal unit (21, 22) through decoupling means (20, 25) of the radio frequency signals and of said control signal on said low frequency carrier;

e) picking up said modulated low frequency carrier with said codified control signal from an end (31) of connection means (16) connected to said at least one receiving antenna (1, 5) by means of second separating means (8,10) of the radio frequency signals from the modulated low frequency carrier with control signal and applying said carrier to the actuators to which said commands are respectively directed, by means of decoder means (11) and interface means (12); said connection means comprising a single transmission cable (16) connected to said at least one antenna (1, 5) and to said at least one internal receiving unit (21, 22).

2. Method, according to claim 1, characterized in that said control signal is codified according to a digital code.

3. Method, according to claim 1, characterized in that the frequency of said low frequency carrier is comprised between zero and a value lower than the lowest frequency of the working signal received by said antenna.

4. Method, according to claim 1, characterized in that the frequency of the low frequency carrier is 36 MHz.

5. Method, according to one or more of the preceeding claims, characterized in that integrated circuits (11, 24) generate, receive and decode said codified signals, said integrated circuits being of the type currently used in remote controls for Television sets, gates and similar devices.

6. Method, according to one or more of the preceeding claims, characterized in that said codifier circuit (24) comprises an M708 integrated circuit made by S.G.S. and said decoder circuit (11) comprises an M490 integrated circuit, made by S.G.S.

7. Method, according to one or more of the preceeding claims, characterized in that signal arrangements generated by each of the transmitted commands are memorized in respective memory cells, each of said memory cell being associated to a push-button in order to recall any command by means of the respective memory cell by depressing the corresponding push-button.

8. Apparatus for transmitting a plurality of control signals in antenna systems, particularly for directly receiving television signals from satellites, such systems comprising at least one receiving antenna (1, 5) having mechanical actuators and connection means connecting said at least one antenna to at least one internal unit for receiving signals from satellites, characterized in that said connection means comprises a single radio frequency transmission cable (16) and in that it furthermore comprises:

a) first circuit means (100) comprising means (23) for generating a low frequency carrier, said low frequency being lower than the lowest frequency of the working signal received by the antenna, and for generating and selecting a plurality of control signals, said first circuit means further comprising means (24) for codifying a selected signal among said plurality of control signal and for modulating said low frequency carrier with said selected codified control signal and applying said modulated carrier to said radio frequency transmission cable (16), first separating means (20, 25) being provided to separate said radio frequency signals from said control signal carried on said low carrier;

b) second circuit means (200) for picking up said low frequency carrier from said transmission cable (16) by means of second separating means (8,10) acting on said radio frequency carrier;

c) means (11) for demodulating and decoding said control signal;

d) interface means (12) for applying said control signal to a respective actuator (2, 3, 6, 29).

9. Apparatus, according to claim 8, characterized in that said first circuit means (100) comprises memory cell assemlies, each of said assemblies being associated to a corresponding push-button and being adapted to memorize and recall the control signal arrangements generated by respective commands sent to said actuators.

10. Apparatus, according to claim 8 or 9, characterized in that it comprises more than one first circuit means (100).

11. Apparatus, according to one or more of claims 8 to 10, characterized in that said first circuit means (100) comprises a panel (23) having a plurality of control push-buttons.

12. Apparatus, according to claim 11, characterized in that said panel (23) is comprised in an integrated circuit remote control.

13. Apparatus, according to claim 12, characterized in that said integrated circuits are M708 and M490 integrated circuits by S.G.S.

14. Apparatus, according to one or more of claims 8 to 13, characterized in that said codifying means comprises low-resolution means and high-resolution means, said low-resolution means being used to operate said "polarotor" device and to switch antennas, said high-resolution means being used to rotate said antenna.

15. Apparatus, according to one or more of claims 8 to 14, characterized in that said first (20,25) and second (8,10) separating means comprise means (32,27) for closing the direct current circuit powering said apparatus with a power voltage supplied by either of said first (100) and second (200) circuit means.