Radio-electric system for locating a given object
First Claim
1. A radio locating system comprising an interrogator having means for transmitting a radio signal to a transponder, said transmitting means including means for modulating said radio signal with a modulation signal having a linearly varying frequency, said transponder including means for receiving said radio signal, means for forming from the received signal, a signal having a component with the same modulation slope as that of the received signal and a frequency shifted in one direction by a predetermined amount characteristic of that transponder, and means for transmitting the signal having said frequency shifted component to said interrogator, said interrogator further including at least two spaced antennas for receiving said signal with said frequency shifted component, means, coupled to said antennas, for deriving a beat signal from the signal received by each antenna and the signal transmitted by said interrogator transmitting means, means for shifting the frequency of at least one of said beat signals by said predetermined amount in a direction opposite to said one direction, a frequency discriminator having an output and an input coupled to said frequency shifting means, means for coupling the signal at said output of said discriminator to said modulating means to control the slope of said modulation signal so that the frequency of said frequency-shifted component is constant, and means for deriving from said beat signals data regarding the bearing of said transponder relative to said interrogator.
0 Assignments
0 Petitions
Accused Products
Abstract
The disclosed system is intended to supply angular and range data regarding the position of an object to be located in a reference system. The system comprises an interrogator which transmits a linearly frequency-modulated signal to a transponder disposed on the object. The transponder is provided with means for shifting the frequency of the received signal in one direction by a predetermined amount characteristic of that transponder and means for retransmitting the received signal. The interrogator further includes a pair of receiving antennas whose signals are used for forming beat signals with the transmitted signal. The interrogator is also provided with means for shifting the frequency of the beat signals in the other direction by the same amount. At least one of the shifted beat signals is applied to a frequency discriminator whose output signal is utilized for controlling the slope of the modulation signal in order to keep the frequency of the shifted beat signal constant.
-
Citations
13 Claims
- 1. A radio locating system comprising an interrogator having means for transmitting a radio signal to a transponder, said transmitting means including means for modulating said radio signal with a modulation signal having a linearly varying frequency, said transponder including means for receiving said radio signal, means for forming from the received signal, a signal having a component with the same modulation slope as that of the received signal and a frequency shifted in one direction by a predetermined amount characteristic of that transponder, and means for transmitting the signal having said frequency shifted component to said interrogator, said interrogator further including at least two spaced antennas for receiving said signal with said frequency shifted component, means, coupled to said antennas, for deriving a beat signal from the signal received by each antenna and the signal transmitted by said interrogator transmitting means, means for shifting the frequency of at least one of said beat signals by said predetermined amount in a direction opposite to said one direction, a frequency discriminator having an output and an input coupled to said frequency shifting means, means for coupling the signal at said output of said discriminator to said modulating means to control the slope of said modulation signal so that the frequency of said frequency-shifted component is constant, and means for deriving from said beat signals data regarding the bearing of said transponder relative to said interrogator.
Specification