Communications: directive radio wave systems and devices (e.g. – Presence detection only – By motion detection
Patent
1984-02-09
1987-09-29
Tubbesing, T. H.
Communications: directive radio wave systems and devices (e.g.,
Presence detection only
By motion detection
342129, 340554, G01S 1356, G01S 1338, G08B 1324
Patent
active
046971840
ABSTRACT:
An outdoor microwave transceiver area intrusion detection system includes circuitry for both amplitude and frequency modulation of the microwave carrier signal pulses, which are transmitted at approximately a 50% duty cycle pulses, from a radar antenna to a target. The return signal is mixed with a portion of the transmitted signal to produce first and second doppler frequency signals which are amplified and sampled during a narrow gating pulse. The two resulting sampled doppler frequency signals are alternately switched, in synchronization with the amplitude and frequency modulation signals, into first and second sample/hold circuits to reconstruct the first and second doppler frequency signals. The reconstructed signals are coupled to a differential amplifier to obtain a "range signal" which is proportional to the phase difference between the first and second doppler signals. The range signal is amplified and used to set an alarm circuit if its amplitude exceeds a certain threshold level for a certain interval of time. Signals from "close in" targets, due to rain on the radome surface and the like, are eliminated by the low value of the range signal. Signals from distant targets are cut off by the narrow gating pulse.
REFERENCES:
patent: 3697985 (1972-10-01), Faris et al.
patent: 3766554 (1973-10-01), Tresselt
patent: 3832709 (1974-08-01), Klein et al.
patent: 3932871 (1976-01-01), Foote
patent: 4527151 (1985-07-01), Byrne
"Modulation Schemes in Low-Cost Microwave Field Sensors", Jefford and Howes, IEEE Transactions on Microwave Theory and Techniques, vol. MTT-31, No. 8, Aug. 1983, pp. 613-623.
"Microprocessor Target Assessment for Microwave Intruder Alarms", Monds et al., 1982 Carnahan Conference on Security Technology, May 12-14, 1982.
Cheal James
Fitzsimmons James R.
Foley Edward J.
Barron Jr. Gilberto
Southwest Microwave
Tubbesing T. H.
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