US3699571A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Instrument landing system using a retrodirective sletten antenna responser
Assignee: TDK Micronas GmbH
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Filing: 1970-11-30
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Granted: 1972-10-17
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Expires: 1990-11-30
Abstract
Abstract A radar responser (beacon) system including an interrogating airborne station which receives range and angle coded replies from an otherwise quiescent ground station. A Sletten antenna is employed at the ground station because of its relative simplicity and unique output phase relationships as a function of the angle of arrival of a received signal. The angle of arrival information of the Sletten Antenna phase relationship is transposed to audio modulation for retransmission back to the airborne unit. The interrogating pulses are ''''played back'''' to an airborne range tracker for range determination, and the Sletten antenna receive signal terminal phase relationship is reduced to the audio domain through the aforementioned modulation process. A relatively simple amplitude detection scheme at the airborne station extracts an angle analog which can be used (typically) for elevation angle information. The system is adapted for the measurement of bearing angles in lieu of elevation angles or may be duplicated for the derivation of analogs of both angular coordinates.
Inventors
- 👤 Lon L Sanders
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 06:53
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/74; G01S13/76; G01S13/765; G01S13/88; G01S13/91; G01S13/913
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
240 words
A radar responser system for determining at least an angle at which said second station is located with respect to a first station; interrogation means within said second station for transmitting relatively a train of short radio frequency interrogation pulses at a predetermined repetition frequency; a Sletten antenna at said first station for receiving said interrogation pulses from said second station, said Sletten antenna having first and second received signal terminals at which energy of the received radio and pulse repetition frequencies is extant, the phase difference between said terminals being a function of said angle; first and second amplitude modulators connected for modulating said energy from said first and second terminals respectively; means for supplying said first amplitude modulator a first low frequency modulation signal to modulate energy from said first signal terminal and for supplying said second amplitude modulator a second low frequency modulation signal to modulate energy from said second signal terminal; combiner means for combining the modulated outputs of said amplitude modulators; antenna means for radiating said combiner output in a pattern capable of being received at said second station; receiving means at said second station for reproducing said interrogation pulse train amplitude modulated by said combined first and second low frequency modulation signals; and means responsive to said receiving means for separately detecting said first and second modulation signals and comparing their relative amplitudes to generate a signal which is a function of said angle.
Claim 2
Dependent Claim
240 words
A radar responser system for determining at least an angle at which said second station is located with respect to a first station; interrogation means within said second station for transmitting relatively a train of short radio frequency interrogation pulses at a predetermined repetition frequency; a Sletten antenna at said first station for receiving said interrogation pulses from said second station, said Sletten antenna having first and second received signal terminals at which energy of the received radio and pulse repetition frequencies is extant, the phase difference between said terminals being a function of said angle; first and second amplitude modulators connected for modulating said energy from said first and second terminals respectively; means for supplying said first amplitude modulator a first low frequency modulation signal to modulate energy from said first signal terminal and for supplying said second amplitude modulator a second low frequency modulation signal to modulate energy from said second signal terminal; combiner means for combining the modulated outputs of said amplitude modulators; antenna means for radiating said combiner output in a pattern capable of being received at said second station; receiving means at said second station for reproducing said interrogation pulse train amplitude modulated by said combined first and second low frequency modulation signals; and means responsive to said receiving means for separately detecting said first and second modulation signals and comparing their relative amplitudes to generate a signal which is a function of said angle.
Claim 3
Dependent Claim
26 words
Apparatus according to claim 1 including radio frequency power amplification means between each of said received signal terminals and the corrEsponding one of said amplitude modulators.
Claim 4
Dependent Claim
57 words
The invention set forth in claim 2 including a pulse generator within said interrogation means at said second station for generating control pulses to time the generation of said radio frequency interrogation pulses, and a range tracking circuit responsive to said control pulses and said receiving means at said second station to produce a distance analog signal.
Claim 5
Dependent Claim
28 words
The invention set forth in claim 2 in which said interrogation pulse repetition frequency is high compared to either of said first and second low frequency modulation signals.
Claim 6
Dependent Claim
60 words
Apparatus according to claim 4 in which said first station is defined as a fixed station, said second station is located on a movable vehicle and said receiving means at said second station includes antenna means having a directivity pattern permitting transmissions to and reception of transmissions from said first station over a predetermined range of positions for said vehicle.
Claim 7
Dependent Claim
56 words
The invention according to claim 5 in which said antenna means forming a part of said second station receiving means is connected to said interrogation means and said receiving means through duplexing means whereby said second station transmits during generation of each discrete interrogation pulse and may receive transmissions from said first station at other times.
Claim 8
Dependent Claim
91 words
Apparatus according to claim 6 in which said means for detecting said first and second modulation signals and comparing their relative amplitudes at said second station includes a boxcar detector responsive to said second station receiving means, first and second bandpass filters tuned to said first and second low frequency modulation signals respectively, first and second amplitude detection means connected to the outputs of said first and second filters respectively and means for differencing the outputs of said amplitude detectors to produce said signal which is a function of said angle.
Claim 9
Dependent Claim
44 words
Apparatus according to claim 7 in which said first and modulation signal comprises + or - 45* phased components and said second modulation signal comprises + or - 45* phased components, and said modulation at said first station is of the vestigal sideband type.
Claim 10
Dependent Claim
43 words
The invention set forth in claim 8 in which said first station is defined as a fixed ground station, said second station is defined as airborne and said angle is the elevation angle of said second station with respect to said first station.
Claim 11
Dependent Claim
39 words
Apparatus according to claim 9 further defined in that said first and second low frequency modulation signals are 90 and 150 cycles respectively, and said interrogation pulse repetition frequency is at least ten times said second modulation signal frequency.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-17 | 1976-04-17 | 1976-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-17 | 1980-04-17 | 1980-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-17 | 1984-04-17 | 1984-10-17 | $7700.00 | Window Closed / Lapsed |