US3708795A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cassegrain antenna mounted in aircraft nose cone
Assignee: BAE Systems PLC
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Filing: 1971-02-10
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Granted: 1973-01-02
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Expires: 1991-02-10
Abstract
Abstract A forward-facing aircraft antenna of modified Cassegrain configuration, having a flat plate main dish and a sub-dish which has a reflecting surface chosen from among surfaces of revolution that require two or more reflections to bring a wave parallel to the axis of revolution to a substantial point focus.
Inventors
- 👤 J Lyons
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:45
CPC Classifications
H; H01; H01Q; H01Q1/00; H01Q1/27; H01Q1/28; H01Q1/281; H01Q19/00; H01Q19/10; H01Q19/18; H01Q19/19; H01Q19/195
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
95 words
A forward-looking aircraft antenna of substantially Cassegrain configuration, comprising a main dish in flat plate form, and a sub-dish forward of the main dish with a reflecting surface in the form of a surface of revolution generated about a fore-and-aft axis passing through the center of the main dish, said sub-dish surface being chosen from the class of surfaces of revolution that require more than a single reflection at said sub-dish to bring a wave approaching from said main dish anD parallel to said axis of revolution to a substantial point focus on said axis.
Claim 2
Dependent Claim
95 words
A forward-looking aircraft antenna of substantially Cassegrain configuration, comprising a main dish in flat plate form, and a sub-dish forward of the main dish with a reflecting surface in the form of a surface of revolution generated about a fore-and-aft axis passing through the center of the main dish, said sub-dish surface being chosen from the class of surfaces of revolution that require more than a single reflection at said sub-dish to bring a wave approaching from said main dish anD parallel to said axis of revolution to a substantial point focus on said axis.
Claim 3
Dependent Claim
15 words
An antenna according to claim 1, wherein the sub-dish also constitutes the external aircraft radome.
Claim 4
Dependent Claim
19 words
An antenna according to claim 1, wherein the chosen surface requires two reflections to achieve a substantial point focus.
Claim 5
Dependent Claim
33 words
An antenna according to claim 3, wherein the sub-dish surface has an equation of the form: x/F (1 - (y/2F)2) - (y/F) Square Root 1 + (y/2F)2 where F is the focal length.
Claim 6
Dependent Claim
30 words
An antenna according to claim 4, wherein the angular spread of the feed to the sub-dish, measured from the axis of revolution of the sub-dish surface, is substantially 36* .
Claim 7
Dependent Claim
51 words
An antenna according to claim 1, wherein the chosen surface requires more than two reflections to achieve a substantial point focus and has an equation of the form: y A(1 - x) + B (1 - x2) where A and B are empirically determined constants for any particular number of reflections.
Claim 8
Dependent Claim
18 words
An antenna according to claim 6, wherein the number of reflections is three, A 1.4226 and B 0.0774.
Claim 9
Dependent Claim
18 words
An antenna according to claim 6, wherein the number of reflections is four, A 0.3358 and B 0.0392.
Claim 10
Dependent Claim
18 words
An antenna according to claim 6, wherein the number of reflections is five, A 0.2751 and B 0.0249.
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) | 1976-01-02 | 1976-07-03 | 1977-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-02 | 1980-07-03 | 1981-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-02 | 1984-07-03 | 1985-01-02 | $7700.00 | Window Closed / Lapsed |