US3761946A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Radio altimeter with rate of height change indication
Assignee: International Standard Electric Corp
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Filing: 1972-01-24
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Granted: 1973-09-25
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Expires: 1992-01-24
Abstract
Abstract An FM/CW radio altimeter of the type which measures altitude as a function of the beat frequency signal resulting from mixing of the received energy against a portion of the transmitted signal. A circuit is included for determining the rate of change of altitude with time. A portion of the beat frequency signal is bandpass filtered and differentiated to reset a digital counter driven by a timing oscillator. The count is sampled and displayed and gives a measure of the rate of change of height of the aircraft. The dh/dt output is itself inherently digital and may therefore be presented in a counter type display. The rate of change signal is derived without differentiating or otherwise processing the output signal of the overall device as fed to a height display.
Inventors
- 👤 R Johanessen
- 👤 J Mun
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:40
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/06; G01S13/08; G01S13/32; G01S13/34; G01S13/345; G01S13/50; G01S13/58; G01S13/60
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
132 words
A rate-of-height-change device for inclusion in a radio altimeter of the frequency modulated type, producing a beat frequency signal characterizing the altitude and available within said radio altimeter, comprising the combination of: a bandpass filter responsive to said beat frequency signal; means responsive to the output of said filter for developing a signal representative of the derivative of the waveshape of said filter output; a timing oscillator having a frequency higher than the frequencies expected in said derivative signal; a digital counter responsive to said timing oscillator to count the cycles thereof; means responsive to said derivative signal to terminate the count of said counter at discrete times whenever said derivative signal attains a predetermined condition; and means for displaying and holding said counter output for a predetermined time for visual observation.
Claim 2
Dependent Claim
132 words
A rate-of-height-change device for inclusion in a radio altimeter of the frequency modulated type, producing a beat frequency signal characterizing the altitude and available within said radio altimeter, comprising the combination of: a bandpass filter responsive to said beat frequency signal; means responsive to the output of said filter for developing a signal representative of the derivative of the waveshape of said filter output; a timing oscillator having a frequency higher than the frequencies expected in said derivative signal; a digital counter responsive to said timing oscillator to count the cycles thereof; means responsive to said derivative signal to terminate the count of said counter at discrete times whenever said derivative signal attains a predetermined condition; and means for displaying and holding said counter output for a predetermined time for visual observation.
Claim 3
Dependent Claim
66 words
Apparatus according to claim 1 in which said means for developing said signal representative of the derivative includes means for deriving a signal representative of the eNvelope of the signal at said filter output, and means for detecting selected inflection points in said envelope and for producing said derivative signal in the form of pulses corresponding in real time to the occurrence of said inflection points.
Claim 4
Dependent Claim
44 words
Apparatus according to claim 2 in which said means for deriving said signal representative of said envelope comprises rectifying means peak detecting the output of said filter, thereby to develop said envelope signal in the form of a signal having relatively sharp minimum values.
Claim 5
Dependent Claim
22 words
Apparatus according to claim 3 in which said rectifying means is followed by amplifier and limiter means for producing said derivative pulses.
Claim 6
Dependent Claim
36 words
Apparatus according to claim 4 in which said derivative pulses are applied as triggering pulses to terminate said count of said counter, and said discrete times are substantially the times of occurrence of said derivative pulses.
Claim 7
Dependent Claim
29 words
Apparatus according to claim 5 including means for inverting said count whereby said display and holding means receives a count directly rather than inversely proportional to said rate-of-height change.
Claim 8
Dependent Claim
36 words
Apparatus according to claim 6 in which said filter is also responsive to a signal representing altitude, separately determined by said radio altimeter, to control the center frequency of said filter as a function of altitude.
Claim 9
Dependent Claim
36 words
Apparatus according to claim 6 in which said filter is also responsive to a signal representing altitude, separately determined by said radio altimeter, to control the passband characteristics of said filter as a function of altitude.
Claim 10
Dependent Claim
35 words
Apparatus according to claim 1 including means for controlling at least the center frequency of said filter as a function of altitude in response to a separately provided altitude-representing signal produced by said radio altimeter.
Claim 11
Dependent Claim
35 words
Apparatus according to claim 1 including means for controlling at least the passband characteristics of said filter as a function of altitude in response to a separately provided altitude-representing signal produced by said radio altimeter.
References Cited (Backward Citations)
US3305862A
Cited
US3522602A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-09-24 | 1977-03-26 | 1977-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-24 | 1981-03-26 | 1981-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-24 | 1985-03-26 | 1985-09-25 | $7700.00 | Window Closed / Lapsed |