DK150041B - TRANSPONDER NAME FOR RADIO ELECTRIC DISTANCE MEASUREMENT - Google Patents

Description

The invention relates to a transponder of the kind described in the preamble of claim 1.

Such a transponder can be used for remote sensing with radio waves. From a main station a 10 possibly modulated carrier is emitted. When detected by the transponder, it emits a response carrier.

This one reaches the main station and the time elapsed is then a measure of the distance.

In this application, it becomes essential to know the transponder's time delay. If the time delay is not well defined, the distance determination will not be accurate. It has been found that even the use of high quality electrical components cannot immediately ensure a well-defined time delay. This is partly because temperature conditions and component aging also play a part.

In addition, US Patent No. 3,290,677 discloses 25 a transponder containing two phase-locked control loops. However, this transponder also contains a 38 KHz reference oscillator and this must be considered a major disadvantage of the circuit. If this oscillator changes frequency, e.g. due to temperature changes, it will degrade the quality of the distance measurement. While there are extremely stable and temperature-compensated crystal oscillators, these are relatively expensive.

The object of the invention is therefore to provide a transponder in which the output signal depends as simply as possible solely on the input signal, so that any possible time delay 5 will be well defined in all conditions. This is achieved when the transponder is constructed as specified in claim 1's design part.

In this construction, it is ensured that the signals transmitted from the transponder 10 are controlled solely by the signal received from the main station. The transponder signals are completely free of unwanted variations due to the various components of the transponder. Both frequency and phase of both a carrier and an auxiliary carrier emitted by the transponder are adjusted by the signals received by the transponder from the main station.

The circuit design ensures that the input amplifier 20 can have a large bandwidth and thus be insensitive to noise phenomena that could otherwise affect its throughput time. If, for some reason, phase changes of the generated signal occur relative to the input signal, this will be automatically corrected in the control loops. This is done without the use of reference oscillators, ie solely on the basis of the incoming signals.

Claims 2 and 3 disclose preferred embodiments, all of which have been found to work well in practice.

In the following, the invention will be described in more detail with reference to the drawing, in which FIG. 1 schematically shows a transponder communication message for distance measurement; FIG. 2 shows a block diagram of the transponder 5 according to the invention, and FIG. 3a, 3b and 3c show schematically different signal spectra, and FIG. 3d shows another view of the signals of FIG. 3c.

The transponder of the invention is intended for distance measurement between a first station or satellite Pi (Fig. 1) and a second station, e.g. a ground station P2.

The first station Pi comprises a transmitter-receiver installation EiRi ·

The second station comprises a transmitter-receiver installation R2E2 · 25 The transmitter Ei emits a sinusoidal carrier e.g.

with an ultra-high frequency with an angular frequency ^ o * which is phase modulated by a high-frequency auxiliary carrier.

The transmitter E2 of station P2, whose function depends on receiving signals transmitted from station 30 Pi to station P2, comprises a generator g2P2 capable of securing transmission from station P2 of an ultra-high frequency carrier with a frequency. which deviates from the frequency of the ultra-high-frequency carrier emitted from the station Pi, as well as a generator for a high-frequency auxiliary carrier 92S2P2 which serves to phase modulate the ultra-high-frequency carrier.

The first station Ρχ receives the phase-modulated ultra-high frequency signals emitted from transmitter E2 and the distance between station Ρχ and station P2 is determined by station Ρχ by comparing the signals received by station Ρχ from station P2 to signals broadcast from the station

Pi

The receiver transmitter R2E2 of the state ion P2 comprises a receiver and transmit antenna 11 (Fig. 2) and an antenna coupler 15 12 arranged to transmit the signals received by the antenna 11 to an input channel 13. This comprises an amplifier 14, the output of which is 15 signals received by the station P2 from the station Ρχ have a frequency spectrum, as shown schematically in FIG. 3a. This spectrum 20 is symbolized by a vector F representing the ultra-high frequency carrier having an angular frequency increase received by station P2 and two vectors f and f of the same length but opposite, representing the phase modulation of the auxiliary carrier, and located on both sides of the the vector F and at a distance from it and in the counter phase thereof representing the frequency of the auxiliary carrier e.g. 1 MHz.

The output signals from the amplifier 14 are applied to a first input 16 of a mixing step 17, the second input 18 of which is the heterodyne input, which is connected to the output 19 of an amplitude modulator 20. A frequency to be modulated is applied to a first input 21 of said modulator. from a 150041 5 1 frequency multiplier 22 and introducing a multiplication factor equal to p1 a frequency produced by a quartz-controlled oscillator 23. The oscillator 23 has a controlled frequency and serves to produce the carrier wave of the station P2. Preferably, a voltage controlled oscillator is used whose nominal frequency is of the magnitude - where <00 is the angular frequency of the ultra-high frequency carrier received by the station P2 and p and q are multiplication factors.

10

The modulation signal applied to a second input 25 of the modulator 20 is the output of a high frequency quartz oscillator 26 or voltage controlled oscillator (VCO), which has a controlled frequency and serves to produce the auxiliary carrier transmitted by the station P2. The circuit 24 connected to the output of the oscillator 23 is divided into a first circuit branch 27 connected to the input of the frequency multiplier 22 and a second circuit branch 28 connected to the input of a second frequency multiplier 29 which introduces a multiplication factor corresponding to q. The output 31 of the frequency multiplier 29 is fed to the input 32 of a circuit designated 33 as a whole, which controls the frequency 25 and the phase of the high frequency oscillator 26, and comprises a phase rotary link 34 which performs a phase rotation of r / 2, a phase comparator 35 and a filter 36 whose output is connected to an input 37 which controls the frequency and phase of the high frequency oscillator 26. Firstly, filter 30 36 eliminates undesirable frequencies from the output of phase comparator 35, and serves to maintain operating conditions for the control loop containing the oscillator 26.

6 15 AND U1 1 The second input 38 of the phase comparator 35 is connected to the output 39 of an intermediate frequency amplifier 41, the input 42 of which is connected to the output 44 of the mixing stage 17. A bandpass filter 5 45 is inserted between the amplifier 41 and the phase comparator 35.

The output 39 of the intermediate frequency amplifier 41 is further connected to the input 46 of a second phase comparator 47, the second input 48 of which is connected to the output 49 of a second amplitude modulator 51, whose input 52 of the frequency to be modulated is connected to the output 31 of the frequency multiplier. 29. The modulation applied to a second input 53 of modulator 15 51 is applied across circuit 54 from the output of high frequency oscillator 26.

The output 55 of the phase comparator 47 is connected via a filter 56 to the control input 57 for the frequency of the oscillator 23.

The carrier frequency transmitted through circuit 24, after multiplying the frequency by a factor m of a multiplier 71, is input to input 72 72 of a phase modulator 73, whose second input 74. is connected to the output of the second oscillator 26, optionally over a multiplier or frequency divider 75. The output 76 of the phase modulator 73 is passed over an inserted amplifier 77 to the antenna coupler 12, 30 which carries the carrier which is phase modulated by the auxiliary carrier to the antenna 11.

The apparatus described works as follows.

7 15004 1 1 The ultra high frequency with the angular frequency α) o which is phase modulated with the high frequency f is received by the antenna 11 and amplified in the amplifier 14 / which may have a large bandwidth and therefore will be almost 5 insensitive to interference - and noise signals that may affect its throughput time. The signals from the amplifier 14 are applied to the input 16 of the mixing step 17, which receives over its input 18 signals coming from the amplitude modulator 20. The frequency 10 to be modulated and applied to the input 21 of the modulator 20 has the value: -e-ω0 p +% 15

The signal is amplitude modulated by a sinusoidal high frequency wave supplied from the oscillator 26, e.g. at a frequency of 1MHz. The spectrum of the signal output from the output 19 of the amplitude modulator 20 is shown in FIG. 3b by the vectors ίχ and f2 having the same magnitude and distance from the frequency to be modulated.

The spectrum of the signal appearing at output 25 44 of mixer 17 is shown in FIG. 3c. It comprises a vector f 3 having a frequency - oo q and of a magnitude, which depends on the shift between the modulated high frequency phase of the signal supplied to the input 16 and the modulated high frequency phase of the signal which the input 18 of the mixing step 17. is added to the spectrum 17. The spectrum further contains the vectors λ 4 and f5 located on both sides of the vector f3 and at the same distance from it, in the example 1MHz shown, corresponding to the amplitude modulation. Furthermore, the spectrum contains the vectors fg and ίη located on both sides of the vector and at the same distance from it, in the example 1 MHz shown, and representing the sidebands due to the phase modulation.

5

After amplification in the medium frequency amplifier 41, the signal is transmitted partly to the input 38 of the phase comparator 35 over the filter 45 leaving only the one in FIG. 3c, the frequency f3 passes, partly to the input 46 of the phase comparator 47.

In the loop designated 61 as a whole containing the mixing step 17, the intermediate frequency amplifier 41, the filter 45, the phase comparator 35, the filter 36, the high frequency oscillator 26 and the amplitude modulator 20, the frequency and phase of the oscillator 26 are controlled by input signals 16 of the mixing stage 17. If for some reason phase shifts occur in the oscillations 20 produced by the oscillator 26 relative to the modulation supplied to the input 16, an error signal will be generated at the output of the phase comparator 35 which corrects the phase of the oscillator 26 to a value corresponding to that to be observed relative to the phase modulated signal received by the station 1 * 2 * In the 62 designated circuit as a whole containing the ultra high frequency oscillator 23, the multiplier 29, the amplitude modulator 51 and the phase comparator 47, the phase of the oscillator 23 is controlled by the ultra-high frequency applied to the input 46 of the phase comparator 4 7th

150041 9 1 The signals applied to the input 48 of this comparator have the same spectrum, except for a frequency converter, as those applied to the input 18. The central portion of the spectrum fed to the input 48, 5 has the frequency: --- ω0 If for some reason undesirable variations occur in the phase of the ultra-high frequency produced by the station P2 by the oscillator 23, an error signal will appear at the output 55 of the phase comparator 47, which corrects the phase of the oscillator 15 23. so that it receives the same position relative to the phase of the ultra-high frequency received by the station P2 coming from the station Ρχ.

In a changed embodiment, the products of the signals supplied to the inputs 16, 21 and 25 respectively will be changed in order. The same applies to the product of signals applied to the inputs 52, 53 and 46, respectively. The fitting modulation at the station P2 may differ from the auxiliary carrier received from the second station Ρχ.

The invention may also apply in a case where the station P2 has means for generating several auxiliary carriers, controlling the frequency and phase of said auxiliary carriers by an auxiliary carrier in the signal emitted from the station P1 and received at the station P2. In one embodiment, the auxiliary carriers can be set in phase relative to the auxiliary carrier received. In a modified 150OA 1 or 1 embodiment, the phase shift of the auxiliary carriers to be emitted from the station P2 is measured relative to the phase of an auxiliary carrier / received from the station Ρχ. The invention may also apply to a phase modulation which is not sinusoidal but of a different type e.g. square, assuming the mean of the modulation is zero.

Claims (3)

1500A1 1 PATENT REQUIREMENT A transponder for a time-sensitive radio communication system and also comprises a main station 5 (Pi) # which emits a phase-modulated UHF carrier, which transmits a UHF response carrier back to the main station, the response carrier being modulated with a local auxiliary carrier generated in accordance with the phase modulation received from the main station, wherein the transponder has a first control loop (62) for controlling a first voltage controlled oscillator (23) for generating the response carrier phase locked to the received carrier, and further having another control loop 15 (61) with a second voltage controlled oscillator (26) for generating a local auxiliary carrier phase locked to the phase modulating auxiliary wave received from the main station, the transponder also comprising an amplifier (14), intermediate frequency amplifier (41) and a phase comparator (47), the first oscillator (23) being controlled by the output of the phase comparator (47) 25, characterized in that (a) the transponder has two circuit branches (27, 28), both connected to the output of the first oscillator (23) to produce a heterodinous signal and a reference signal respectively, each branch (27, 28) ) contains an amplitude modulator 30 (20, 51) arranged so that the sum of the frequencies of said signals corresponds to the frequency of the incoming carrier, b) the amplitude modulators (20, 51) are both connected.