Distance measuring equipment
First Claim
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1. Distance measuring equipment for measuring the distance from an airborne interrogator to a ground based transponder comprising;
- an interrogator encoder for providing a linear frequency modulated pulse modulated signal with selectable slope sign;
interrogator transmitter means for mixing a preselected radio frequency signal with the interrogator encoder pulse and transmitting the resulting radio frequency pulse;
transponder receiver means for receiving interrogator transmissions and providing an intermediate frequency output in response thereto;
a matched pulse compression filter coupled to the transponder receiver for providing time compression and signal to noise gain for intermediate frequency signals having a preselected center frequency and linear frequency modulated frequency modulation with separate detection for both modulation slope signs;
transponder decoder means coupled to the pulse compression filter for detecting the arrival of the leading edge of a received pulse and providing an output pulse indicating said arrival;
transponder transmitter means coupled to said transponder decoder means for transmitting a pulse of radio frequency signals at a preselected frequency in response to the decoder output;
interrogator receiver means for receiving transponder transmissions and providing an intermediate frequency output in response thereto;
interrogator decoder means coupled to the interrogator receiver for detecting the arrival of a transponder pulse having a preselected center frequency and providing an output indicating said arrival; and
range calculating means coupled to the interrogator encoder and the interrogator decoder for measuring the time between an interrogator transmission and reception of a transponder transmission and providing an output proportional to the distance from the interrogator to the transponder.
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Abstract
Disclosed is improved distance measuring equipment comprising an airborne FM coded, chirp, interrogator transmitter in combination with a weighted matched receiver in a ground transponder. The airborne transmitter produces a long low power frequency modulated output pulse. Detection in the transponder receiver is accomplished by pulse compression matched filter techniques.
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Citations
5 Claims
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1. Distance measuring equipment for measuring the distance from an airborne interrogator to a ground based transponder comprising;
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an interrogator encoder for providing a linear frequency modulated pulse modulated signal with selectable slope sign; interrogator transmitter means for mixing a preselected radio frequency signal with the interrogator encoder pulse and transmitting the resulting radio frequency pulse; transponder receiver means for receiving interrogator transmissions and providing an intermediate frequency output in response thereto; a matched pulse compression filter coupled to the transponder receiver for providing time compression and signal to noise gain for intermediate frequency signals having a preselected center frequency and linear frequency modulated frequency modulation with separate detection for both modulation slope signs; transponder decoder means coupled to the pulse compression filter for detecting the arrival of the leading edge of a received pulse and providing an output pulse indicating said arrival; transponder transmitter means coupled to said transponder decoder means for transmitting a pulse of radio frequency signals at a preselected frequency in response to the decoder output; interrogator receiver means for receiving transponder transmissions and providing an intermediate frequency output in response thereto; interrogator decoder means coupled to the interrogator receiver for detecting the arrival of a transponder pulse having a preselected center frequency and providing an output indicating said arrival; and range calculating means coupled to the interrogator encoder and the interrogator decoder for measuring the time between an interrogator transmission and reception of a transponder transmission and providing an output proportional to the distance from the interrogator to the transponder. - View Dependent Claims (2, 3, 4)
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5. In distance measuring equipment for measuring the distance from an airborne interrogator transmitter to a ground based transponder receiver, the method of providing pulsed radio frequency interrogation signals comprising:
- time expanding and linear frequency modulating said radio frequency pulses transmitted by said interrogator transmitter;
time compressing and frequency demodulating said radio frequency pulses received by said transponder; and
reversing said linear frequency modulation of said pulses on alternate interrogations in order to cancel transmission errors.
- time expanding and linear frequency modulating said radio frequency pulses transmitted by said interrogator transmitter;
Specification