US3969725A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Distance measuring equipment
Assignee: United States Department of Transportation
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Filing: 1974-06-12
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Granted: 1976-07-13
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Expires: 1994-06-12
Abstract
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.
Inventors
- 👤 James Benedict Couvillon
- 👤 William Dorsey Daniels
- 👤 Ronald Lee Gassner
- 👤 Robert Allen Maher
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 12:34
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/06; G01S13/08; G01S13/10; G01S13/26; G01S13/28; G01S13/282; G01S13/74; G01S13/76
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
254 words
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.
Claim 2
Dependent Claim
254 words
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.
Claim 3
Dependent Claim
66 words
Distance measuring equipment according to claim 1 wherein the interrogator encoder comprises a local oscillator, a one-shot for providing a preselected width video pulse, a mixer coupled to the local oscillator and one shot for providing a pulse of intermediate frequency signal having the preselected width, and a surface wave device pulse expander coupled to the mixer for providing a time expanded frequency modulated output pulse.
Claim 4
Dependent Claim
17 words
Distance measuring equipment according to claim 1 wherein the pulse compression filter comprises a surface wave device.
Claim 5
Dependent Claim
30 words
Distance measuring equipment according to claim 1 wherein the transponder receiver means includes a limiter amplifier for limiting the amplitude of the intermediate frequency output to a single preselected level.
Claim 6
Dependent Claim
75 words
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.
Claim 7
Dependent Claim
75 words
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.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-07-13 | 1980-01-12 | 1980-07-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-07-13 | 1984-01-12 | 1984-07-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-07-13 | 1988-01-12 | 1988-07-13 | $7700.00 | Window Closed / Lapsed |