US4894659A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Radar altimeter systems
Assignee: Smiths Group PLC
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Filing: 1988-10-04
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Granted: 1990-01-16
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Expires: 2008-10-04
Abstract
Abstract An aircraft microwave altimeter system has a threshold detector with two parallel channels that provide two sets of output signals at two different levels of sensitivity. The signals at the higher sensitivity are supplied to a display whereas those at the lower sensitivity are supplied to a navigation system. A comparator indicates a fault in the system if the two sets of output signals differ by more than a predetermined amount.
Inventors
- 👤 Frank P. Andrews
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 00:06
CPC Classifications
G; G01; G01S; G01S7/00; G01S7/02; G01S7/28; G01S7/285; G01S7/292; G01S7/2921; G01S7/2922; G01S13/00; G01S13/02; G01S13/06; G01S13/08; G01S13/10; G01S7/34; G01S7/40; G01S7/4004; G01S7/4021; G01S13/88; G01S13/882
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
166 words
An aircraft microwave altimeter system comprising: means for transmitting microwave signals to the ground; means for receiving microwave signal reflected from the ground and objects on the ground; means for deriving from the received signals information as to the height of the aircraft above the ground or objects on the ground; threshold detector means, said threshold detector means being arranged to provide a first set of output signals in accordance with height at a first threshold level, and a second set of output signals in accordance with height at a second threshold level greater than said first threshold level; display means; means supplying said first set of output signals to said display means; navigation means; and means supplying said second set of output signals to said navigation means, such that said navigation means is supplied with signals representative of the height of the aircraft above ground whereas said display means is supplied with signals representative of the height of the aircraft above objects on the ground.
Claim 2
Dependent Claim
166 words
An aircraft microwave altimeter system comprising: means for transmitting microwave signals to the ground; means for receiving microwave signal reflected from the ground and objects on the ground; means for deriving from the received signals information as to the height of the aircraft above the ground or objects on the ground; threshold detector means, said threshold detector means being arranged to provide a first set of output signals in accordance with height at a first threshold level, and a second set of output signals in accordance with height at a second threshold level greater than said first threshold level; display means; means supplying said first set of output signals to said display means; navigation means; and means supplying said second set of output signals to said navigation means, such that said navigation means is supplied with signals representative of the height of the aircraft above ground whereas said display means is supplied with signals representative of the height of the aircraft above objects on the ground.
Claim 3
Dependent Claim
46 words
An aircraft microwave altimeter system according to claim 1, wherein said threshold detector means includes two parallel threshold detector channels, and wherein said two detector channels are arranged to supply the respective first and second sets of output signals in respect of the same received signals.
Claim 4
Dependent Claim
56 words
An aircraft microwave altimeter system according to claim 1 wherein the said threshold detector means has a single channel which selectively adjustable in threshold sensitivity, and wherein the said threshold detector means is arranged to supply alternately output signals at one sensitivity level to said display means and at another lower sensitivity to said navigation means.
Claim 5
Dependent Claim
21 words
An aircraft microwave altimeter system according to claim 1, wherein the said means for transmitting microwave signals transmits pulsed microwave signals.
Claim 6
Dependent Claim
46 words
An aircraft microwave altimeter system according to claim 3, wherein the said means for transmitting microwave signals transmits pulsed microwave signals, and wherein said threshold detector means supplies information derived from a greater number of reflected pulses to said display means than to said navigation means.
Claim 7
Dependent Claim
66 words
An aircraft microwave altimeter according to claim 1, wherein the said threshold detector means is responsive to the magnitude of the received signals, such that the said first set of output signals is provided in response to received signals above a first magnitude and said second set of output signals is provided in response to received signals above a second magnitude greater than the first magnitude.
Claim 8
Dependent Claim
62 words
An aircraft microwave altimeter system according to claim 6, wherein, said threshold detector means includes amplifier means, said amplifier means being arranged to produce two sets of intermediate output signals at different gains and wherein the threshold detector means passes to said display means and navigation means respectively those of the two sets of intermediate output signals above the same threshold level.
Claim 9
Dependent Claim
71 words
An aircraft microwave altimeter system according to claim 4, wherein said threshold detector means is responsive to the duration of the received signals, such that said first set of output signals is provided in response to received signals longer than a first duration and said second set of output signals is provided in response to received signals longer than a second duration, said second duration being longer than said first duration.
Claim 10
Dependent Claim
71 words
An aircraft microwave altimeter system according to claim 6, wherein said threshold detector means is responsive to both the magnitude and duration of the received signals by integration, and wherein the said first set of output signals is provided in response to integrated signals above a first magnitude and said second set of output signals is provided in response to integrated signals above a second magnitude greater than, said first magnitude.
Claim 11
Dependent Claim
56 words
An aircraft microwave altimeter system according to claim 1 including comparator means, means connecting said comparator means to receive said first and second sets of output signals, and said comparator means being arranged to provide an indication when there is a difference between said first and second sets of output signals greater than a predetermined difference.
Claim 12
Dependent Claim
54 words
An aircraft microwave altimeter system according to claim 10, wherein the system is arranged to supply only one of said sets of output signals to both the display means and the navigation means when the indication provided by said comparator means indicates that the other one of said sets of output signals is faulty.
Claim 13
Dependent Claim
35 words
An aircraft microwave altimeter system according to claim 11, including means to increase the sensitivity of said threshold detector means if the said one set of output signals is said second set of output signals.
Claim 14
Dependent Claim
29 words
An aircraft microwave altimeter system according to claim 1, including means to modify the threshold levels of said threshold detector means in accodance with the height of the aircraft.
Claim 15
Dependent Claim
33 words
An aircraft microwave altimeter system according to claim 1 including means to modify the threshold levels of said threshold detector means in accordance with the terrain conditions over which the aircraft is flying.
Claim 16
Dependent Claim
30 words
An aircraft microwave altimeter system according to claim 1 including means to modify the threshold levels of said threshold detector means in accordance with the flight conditions of the aircraft.
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) | 1993-01-15 | 1993-07-17 | 1994-01-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-15 | 1997-07-17 | 1998-01-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-15 | 2001-07-17 | 2002-01-16 | $7700.00 | Window Closed / Lapsed |