Patent US4389647A successfully refreshed from Google Patents.
US4389647A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Doppler discrimination of aircraft targets
Assignee: United States Department of the Army
•
Filing: 1980-12-22
•
Granted: 1983-06-21
•
Expires: 2000-12-22
Abstract
Abstract Two discriminator circuits are used with Doppler radars to indicate the t of aircraft in the radar beam based on the modulating effect of the aircraft rotor or propeller on the Doppler return signal. The increase in the Doppler signal when a rotor or propeller becomes orthogonal to the incident radar beam causes a spike in the detected Doppler signal. The frequency of such spikes is an indication of the make and model aircraft being observed and the circuitry comprises means for sensing such frequency and operating one of a plurality of indicators if such frequency corresponds to that of a known rotor or propeller frequency of a particular make and model aircraft corresponding to that indicator.
Inventors
- 👤 Michael A. Fanuele
- 👤 Joseph A. McCray
- 👤 Otto F. Rittenbach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 15:34
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/02; G01S13/50; G01S13/58; G01S13/581; G01S7/00; G01S7/02; G01S7/41; G01S7/415
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
245 words
A Doppler radar capable of discriminating between different types of aircraft having rotating elements including circuitry for sensing the occurrence of increases in the Doppler signal amplitude of target returns resulting from increases in cross section of the rotating elements as they become orthogonal to the incident radar beam of said radar, said circuitry comprising, Doppler detector means for detecting the Doppler signal of said radar including a direct reference voltage indicative of the body of said aircraft and a spike frequency component indicative of the orthogonal rotating element of a particular aircraft type, bandpass filter means coupled to the Doppler detector, said bandpass filter means having a wide passband that blocks the direct voltage and passes the spike frequency component, a threshold circuit and a pulse stretcher connected in cascade to the output of said bandpass filter, said threshold circuit providing an output pulse upon the occurrence of said spike frequency above a set threshold, a microprocessor adapted to receive the output of said pulse stretcher, a clock connected to said microprocessor, and a plurality of indicators connected to the output of said microprocessor, each indicator being associated with a respective aircraft type, said microprocessor being adapted to count the number of stretched pulses occurring in a predetermined time period determined by the frequency of said clock and to operate an indicator if the frequency of said stretched pulses corresponds closely to the rotating element spike frequency of an aircraft represented by that indicator.
Claim 2
Dependent Claim
245 words
A Doppler radar capable of discriminating between different types of aircraft having rotating elements including circuitry for sensing the occurrence of increases in the Doppler signal amplitude of target returns resulting from increases in cross section of the rotating elements as they become orthogonal to the incident radar beam of said radar, said circuitry comprising, Doppler detector means for detecting the Doppler signal of said radar including a direct reference voltage indicative of the body of said aircraft and a spike frequency component indicative of the orthogonal rotating element of a particular aircraft type, bandpass filter means coupled to the Doppler detector, said bandpass filter means having a wide passband that blocks the direct voltage and passes the spike frequency component, a threshold circuit and a pulse stretcher connected in cascade to the output of said bandpass filter, said threshold circuit providing an output pulse upon the occurrence of said spike frequency above a set threshold, a microprocessor adapted to receive the output of said pulse stretcher, a clock connected to said microprocessor, and a plurality of indicators connected to the output of said microprocessor, each indicator being associated with a respective aircraft type, said microprocessor being adapted to count the number of stretched pulses occurring in a predetermined time period determined by the frequency of said clock and to operate an indicator if the frequency of said stretched pulses corresponds closely to the rotating element spike frequency of an aircraft represented by that indicator.
Claim 3
Dependent Claim
59 words
The Doppler radar of claim 1 wherein said Doppler signal comprises quadrature I and Q channels and wherein said detector means comprises a pair of square law detectors having their inputs connected to respective said I and Q channels and an adder connected to the outputs of said channels, the output of said adder being the detected Doppler signal.
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) | 1986-06-20 | 1986-12-20 | 1987-06-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-06-20 | 1990-12-20 | 1991-06-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-06-20 | 1994-12-20 | 1995-06-21 | $7700.00 | Window Closed / Lapsed |