Transponder for radiocommunication system, particularly for measuring the distance between two stations

• US 4,183,022 A
• Filed: 06/02/1977
• Issued: 01/08/1980
• Est. Priority Date: 06/03/1976
• Status: Expired due to Term

• Current Assignee: Dassault Electronique
• Original Assignee: Electronique Marcel Dassault
• Inventors: Schumperli, Max, Pouzet, Alain, Baudard, Thierry
• Primary Examiner(s): Richardson, Robert L.
• Assistant Examiner(s): Ng, Jin F.
• Application Number:
  US05/803,115
• Time in Patent Office: 950 Days
• Field of Search: 325/3, 325/7, 325/8, 325/17, 325/47, 325/48, 325/50-61, 325/346, 325/63, 325/418-421, 343/5 AF, 343/6.5 SS, 343/6.8 R, 343/14, 343/17.5, 343/6.5 R, 340/152 T
• US Class Current: 342/174
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement

Abstract

A system for measuring the distance between an interrogating station and a transponder station comprises, at the latter station, a receiver for a phase-modulated UHF wave emitted by the interrogating station and a transmitter for sending back an outgoing main carrier modulated in phase by a locally generated subcarrier. A first oscillator generates a wave whose frequency is a subharmonic of the frequencies of both the incoming and the outgoing main carrier and from which there are derived, besides this outgoing carrier, a heterodyning oscillation and a reference oscillation which are both amplitude-modulated by the output of a second oscillator whose frequency matches that of the incoming subcarrier and which also serves as a source of the locally generated outgoing subcarrier. The amplitude-modulated heterodyning oscillation is mixed with the incoming carrier wave to produce an i-f oscillation with a central frequency matching that of the reference oscillation and with two pairs of sidebands respectively due to the phase modulation of the incoming carrier and to the amplitude modulation of the heterodyning oscillation. The first oscillator is provided with a phase-locking loop including a phase comparator which receives the i-f oscillation and the amplitude-modulated reference oscillation; the same i-f oscillation, freed from its sidebands, is compared with the unmodulated reference oscillation to yield a corrective signal for adjusting the frequency and phase of the second oscillator.

Claims

1. In a radiocommunication system including an interrogating station transmitting a phase-modulated UHF carrier wave and a transponder station responsive to said carrier wave for sending back a main UHF carrier phase-modulated by a locally generated subcarrier,

the improvement wherein said transponder station comprises:

oscillation-generating means including a first voltage-controlled oscillator for producing said main UHF carrier;

a subcarrier source including a second voltage-controlled oscillator;

receiving means for intercepting an incoming UHF carrier wave transmitted by said interrogating station;

circuit means with two branches connected to said first oscillator for respectively producing in one of said branches a heterodyning oscillation and in the other of said branches a reference oscillation with frequencies whose sum equals the frequency of said incoming carrier wave;

amplitude-modulating means connected to said branches and to said second oscillator for modulating the amplitudes of said heterodyning oscillation and of said reference oscillation with an output oscillation of said second oscillator, said output oscillation having a frequency equaling the phase-modulation frequency of said incoming carrier wave;

mixer means with inputs connected to said one of said branches and to said receiving means for deriving from said incoming carrier wave and from the amplitude-modulated heterodyning oscillation a phase-modulated and amplitude-modulated i-f oscillation having the same frequency as said reference oscillation;

first phase-comparison means with input connections to said mixer means and to said other of said branches for detecting phase difference between said i-f oscillation and said reference oscillation and for deriving therefrom an error signal fed to said first oscillator for introducing compensatory phase changes in said heterodyning and reference oscillations;

filter means connected to said mixer means for suppressing the sidebands due to the phase and amplitude modulations of said i-f oscillation;

second phase-comparison means with an output connection to said second oscillator and with input connections to said filter means and to said other of said branches for receiving therefrom said i-f oscillation and said reference oscillation in substantially unmodulated form and for deriving from their phase difference a corrective signal controlling the phase of said output oscillation;

phase-modulating means connected to said oscillation-generating means and to said subcarrier source for producing a phase-modulated outgoing UHF carrier stabilized to frequency and phase by said incoming carrier wave; and

transmitting means connected to said phase-modulating means for emitting said outgoing carrier.

2. The improvement defined in claim 1 wherein said first oscillator has an operating frequency subharmonically related to the frequency of said incoming carrier wave, said branches including respective frequency multipliers.

3. The improvement defined in claim 2 wherein said amplitude-modulating means comprises an amplitude modulator in each of said branches downstream of the respective frequency multiplier.

4. The improvement defined in claim 3 wherein one input connection of said second phase-comparison means extends from a point of said other of said branches located between the frequency multiplier and the amplitude modulator thereof.

5. The improvement defined in claim 4 wherein said one input connection includes a 90°

phase shifter.