US3946385A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interferometric navigation and guidance system
Assignee: United States Department of Transportation
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Filing: 1975-01-20
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Granted: 1976-03-23
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Expires: 1995-01-20
Abstract
Abstract This invention comprises an interferometric technique for the one-way transmission of bearing angle information to an unlimited number of mobile receivers. In accordance with the invention the angle related path length difference, between transmitters located at either end of an interferometer baseline, to a mobile receiver is measured in wavelengths at a modulation frequency.
Inventors
- 👤 Harold I. Ewen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 22:06
CPC Classifications
G; G01; G01S; G01S1/00; G01S1/02; G01S1/08; G01S1/20; G01S1/30; G01S1/302
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
130 words
A method of intermediate frequency interferometry comprising the steps of: generating a first carrier frequency; generating a second carrier frequency; generating a modulation signal; employing the modulation signal to generate a first sideband frequency relative to the first carrier frequency and a second sideband frequency relative to the second carrier frequency, each sideband frequency having the same frequency and phase relationship relative to its carrier frequency; transmitting the carrier frequencies and their related sideband frequencies from respective points located on a common baseline; receiving and separating the transmitted signals at a single point; extracting the modulation frequency from each carrier and its related sideband; and comparing the phase of the extracted modulation frequencies to obtain an indication of the bearing angle between the point of signal reception and the baseline.
Claim 2
Independent Claim
130 words
A method of intermediate frequency interferometry comprising the steps of: generating a first carrier frequency; generating a second carrier frequency; generating a modulation signal; employing the modulation signal to generate a first sideband frequency relative to the first carrier frequency and a second sideband frequency relative to the second carrier frequency, each sideband frequency having the same frequency and phase relationship relative to its carrier frequency; transmitting the carrier frequencies and their related sideband frequencies from respective points located on a common baseline; receiving and separating the transmitted signals at a single point; extracting the modulation frequency from each carrier and its related sideband; and comparing the phase of the extracted modulation frequencies to obtain an indication of the bearing angle between the point of signal reception and the baseline.
Claim 3
Dependent Claim
38 words
The method of claim 1 wherein the step of transmitting further includes: simultaneousely delivering respective carrier and related sideband signals to a pair of antennas separated by a distance which is one wavelength at the common modulation frequency.
Claim 4
Dependent Claim
189 words
A passive direction finding system comprising: means for generating a first carrier frequency signal; means for generating at least a second carrier frequency signal; means for generating a modulation signal at a frequency lower than any of said carrier frequency signals; modulator means responsive to each of said carrier frequency signals and to said modulation signal for generating sideband signals for said first and second carrier frequency signals; means for respectively transmitting said carrier signals and associated sideband signals, said transmitting means each including an antenna located at either end of a baseline, said antennas being separated by a nominal distance equivalent to the wavelength of the said modulation frequency; and means for receiving the transmitted carrier and associated sideband signals, said receiving means generating a modulation frequency signal commensurate with the frequency difference between each transmitter carrier frequency signal and its associated transmitted sideband signal, the phase difference between the modulation signal derived from the first carrier and its sideband and the modulation signal derived from the second carrier and its sideband being commensurate with the bearing angle from the receiver to the antennas located on the baseline.
Claim 5
Dependent Claim
189 words
A passive direction finding system comprising: means for generating a first carrier frequency signal; means for generating at least a second carrier frequency signal; means for generating a modulation signal at a frequency lower than any of said carrier frequency signals; modulator means responsive to each of said carrier frequency signals and to said modulation signal for generating sideband signals for said first and second carrier frequency signals; means for respectively transmitting said carrier signals and associated sideband signals, said transmitting means each including an antenna located at either end of a baseline, said antennas being separated by a nominal distance equivalent to the wavelength of the said modulation frequency; and means for receiving the transmitted carrier and associated sideband signals, said receiving means generating a modulation frequency signal commensurate with the frequency difference between each transmitter carrier frequency signal and its associated transmitted sideband signal, the phase difference between the modulation signal derived from the first carrier and its sideband and the modulation signal derived from the second carrier and its sideband being commensurate with the bearing angle from the receiver to the antennas located on the baseline.
Claim 6
Dependent Claim
50 words
The apparatus of claim 3 wherein said receiving means comprises: means for heterodyning each carrier with its associated sideband to generate signals at the said modulation frequency; and phase detector means responsive to said signals at the modulation frequency for providing an output signal commensurate with the phase difference therebetween.
Claim 7
Dependent Claim
45 words
The apparatus of claim 3 wherein said transmitting means includes: a pair of antennas spaced at either end of a baseline; and means for simultaneously delivering a carrier frequency and a single related sideband signal frequency from said modulator means to each of said antennas.
Claim 8
Dependent Claim
45 words
The apparatus of claim 4 wherein said transmitting means includes: a pair of antennas spaced at either end of a baseline; and means for simultaneously delivering a carrier frequency and a single related sideband signal frequency from said modulator means to each of said antennas.
References Cited (Backward Citations)
US3665468A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-03-23 | 1979-09-22 | 1980-03-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-23 | 1983-09-22 | 1984-03-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-23 | 1987-09-22 | 1988-03-23 | $7700.00 | Window Closed / Lapsed |