Edward J Foley

US Patent:

46971840, Sep 29, 1987

Filed:

Feb 9, 1984

Appl. No.:

6/578539

Inventors:

James Cheal - Tempe AZ
James R. Fitzsimmons - Tempe AZ
Edward J. Foley - Tempe AZ

Assignee:

Southwest Microwave - Tempe AZ

International Classification:

G01S 1356
G01S 1338
G08B 1324

US Classification:

342 28

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.