US4423420A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cancellation of group delay error by dual speed of rotation
Assignee: AEG Bayly Inc
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Filing: 1981-05-06
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Granted: 1983-12-27
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Expires: 2001-05-06
Abstract
Abstract Radio direction finders using the principle of periodic scanning of a circular array inherently display a bearing error related to the group delay through the receiving, detection and evaluation process. Correcting by subtracting a constant θ o is simple but it is difficult to keep θ o constant. The present invention cancels the group delay error instead of compensating for it with a predetermined constant. Scanning is done at angular velocities Ω 1 and Ω 2 for m turns and n turns respectively. The parameters are related by the formulae ω.sub.2 /ω.sub.1 =m/n (1) n-m=1 (2) Group delay errors are cancelled by computing the true bearing from the formula nθ.sub.2 -mθ.sub.1 =θ where θ 1 and θ 2 are the bearing readings at ω 1 and ω 2 respectively and θ is the true bearing of the radio target.
Inventors
- 👤 Zdzistaw A. A. Krajewski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 12:56
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/02; G01S3/14; G01S3/58
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
134 words
A radio direction finding method comprising scanning a circular antenna array alternately at first and second different angular velocities ω 1 and ω 2 , scanning at angular velocity ω 1 being done for m turns and scanning at angular velocity ω 2 being done for n turns, the parameters m, n, ω 1 and ω 2 being related by the formulae ω.sub.2 /ω.sub.1 =m/n (1) and n-m=1 (2) whereby a cancellation of group delay errors in receiving equipment connected to the antenna is obtained by computing the true bearing of a radio target from the formula nθ.sub.2 -mθ.sub.1 =θ (3) where θ 1 and θ 2 are radio target bearing readings obtained at the angular velocities ω 1 and ω 2 respectively and θ is the true bearing angle of said radio target.
Claim 2
Dependent Claim
134 words
A radio direction finding method comprising scanning a circular antenna array alternately at first and second different angular velocities ω 1 and ω 2 , scanning at angular velocity ω 1 being done for m turns and scanning at angular velocity ω 2 being done for n turns, the parameters m, n, ω 1 and ω 2 being related by the formulae ω.sub.2 /ω.sub.1 =m/n (1) and n-m=1 (2) whereby a cancellation of group delay errors in receiving equipment connected to the antenna is obtained by computing the true bearing of a radio target from the formula nθ.sub.2 -mθ.sub.1 =θ (3) where θ 1 and θ 2 are radio target bearing readings obtained at the angular velocities ω 1 and ω 2 respectively and θ is the true bearing angle of said radio target.
Claim 3
Dependent Claim
44 words
A method as claimed in claim 1 wherein all the terms in equation (3) are multiplied by a constant k so that knθ.sub.2 -kmθ.sub.1 =kθ (4) and bearing readings are integrated over a number of scanning periods to eliminate errors caused by random noise.
Claim 4
Dependent Claim
142 words
A radio direction finding system comprising a circular antenna array, means for scanning the antenna array alternately at first and second different angular velocities ω 1 and ω 2 , scanning at angular velocity ω 1 being done for m turns and scanning at angular velocity ω 2 being done for n turns, the parameters m, n, ω 1 and ω 2 being related by the formulae ω.sub.2 /ω.sub.1 =m/n (1) and n-m=1 (2) whereby a cancellation of group delay errors in receiving equipment connected to the antenna is obtained by means for computing the true bearing of a radio target from the formula i nθ.sub.2 -mθ.sub.1 =θ (3) where θ 1 and θ 2 are radio target bearing readings obtained at the angular velocities ω 1 and ω 2 respectively and θ is the true bearing angle of said radio target.
Claim 5
Dependent Claim
142 words
A radio direction finding system comprising a circular antenna array, means for scanning the antenna array alternately at first and second different angular velocities ω 1 and ω 2 , scanning at angular velocity ω 1 being done for m turns and scanning at angular velocity ω 2 being done for n turns, the parameters m, n, ω 1 and ω 2 being related by the formulae ω.sub.2 /ω.sub.1 =m/n (1) and n-m=1 (2) whereby a cancellation of group delay errors in receiving equipment connected to the antenna is obtained by means for computing the true bearing of a radio target from the formula i nθ.sub.2 -mθ.sub.1 =θ (3) where θ 1 and θ 2 are radio target bearing readings obtained at the angular velocities ω 1 and ω 2 respectively and θ is the true bearing angle of said radio target.
Claim 6
Dependent Claim
38 words
A system as claimed in claim 3 wherein ω 1 and ω 2 are obtained by dividing an output frequency ω o of an oscillator by the factors m and n respectively in first and second frequency dividers.
Claim 7
Dependent Claim
31 words
A system as claimed in claim 4 wherein switching means is provided for alternately connecting said dividers to the antenna array via an antenna scanning drive and an antenna selector switch.
Claim 8
Dependent Claim
56 words
A system as claimed in claim 5 wherein consecutive pairs of antenna elements are connected via the antenna selector switch to a twin-channel receiver, said twin-channel receiver having a pair of outputs connected to inputs of a phase detector having an output connected to a bearing processor which, in turn, is connected to a bearing display.
Claim 9
Dependent Claim
17 words
A system as claimed in claim 6 wherein the frequency ω o of the oscillator is variable.
References Cited (Backward Citations)
US3950753A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-12-26 | 1987-06-27 | 1987-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-12-26 | 1991-06-27 | 1991-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-12-26 | 1995-06-27 | 1995-12-27 | $7700.00 | Window Closed / Lapsed |