US3845486A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Doppler microwave landing systems
Assignee: BAE Systems Electronics Ltd
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Filing: 1973-01-03
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Granted: 1974-10-29
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Expires: 1993-01-03
Abstract
Abstract In a ground station providing guidance to aeroplanes, microwave energy is transmitted from a reference aerial and a vertical array of radiating elements along which the signal is commutated. The frequency of the transmitted signal supplied to the array is offset positively or negatively according to the direction of scan with respect to the signal fed to the reference aerial. The doppler shift between the signal from the reference aerial and the signal from the array as detected in an aircraft indicates elevation of the aircraft. Reversal of the frequency applied to the array is arranged to occur at a crest or a trough of the doppler frequency, so that discontinuities or cusps are not produced in the doppler signal at this time.
Inventors
- 👤 J Birchenough
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 18:37
CPC Classifications
G; G01; G01S; G01S1/00; G01S1/02; G01S1/08; G01S1/38; G01S1/40
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
149 words
A ground station of a doppler microwave radar system comprising an aerial array having a plurality of elements and adjacent one end of said array a reference aerial, transmitter means providing the reference aerial with a reference signal and the aerial array with a scanned signal frequency which is offset by a predetermined offset frequency from the reference signal, commutator means operative for feeding said scanned signal sequentially to the elements of the array so that a point from which signal transmission occurs is scanned from one end to the other of said array and back again, and means operative to change the scanned frequency by twice the offset frequency when that element of the array closest to the reference aerial is fed by said commutator and when the rate of change of amplitude of the beat frequency difference between the reference frequency and the scanned frequency is zero.
Claim 2
Dependent Claim
149 words
A ground station of a doppler microwave radar system comprising an aerial array having a plurality of elements and adjacent one end of said array a reference aerial, transmitter means providing the reference aerial with a reference signal and the aerial array with a scanned signal frequency which is offset by a predetermined offset frequency from the reference signal, commutator means operative for feeding said scanned signal sequentially to the elements of the array so that a point from which signal transmission occurs is scanned from one end to the other of said array and back again, and means operative to change the scanned frequency by twice the offset frequency when that element of the array closest to the reference aerial is fed by said commutator and when the rate of change of amplitude of the beat frequency difference between the reference frequency and the scanned frequency is zero.
Claim 3
Dependent Claim
96 words
A ground station as claimed in claim 1, wherein the reference frequency and the scanned frequency are fed to a phase discriminator operative when the signals applied thereto are in phase or in anti-phase to provide an output signal to gating means fed also from the commutator means with a gating signal when that element of said Array closest to the reference aerial is fed from said commutator, the gating means being effective for providing a gating signal to effect a frequency change of the scanning frequency when coincident signals are applied to said gating means.
Claim 4
Dependent Claim
33 words
A ground station as claimed in claim 1, wherein a digitiser is provided to introduce from time to time phase changes in the phase relationship between the reference frequency and the scanning 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) | 1977-10-28 | 1978-04-29 | 1978-10-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-10-28 | 1982-04-29 | 1982-10-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-10-28 | 1986-04-29 | 1986-10-29 | $7700.00 | Window Closed / Lapsed |