Ranging quadrature doppler microwave intrusion alarm system

Abstract

Movement of an object (intruder) in a specified area is sensed by transmitting microwave energy from an antenna (10) that also receives energy reflected from the intruder, where the received energy is quadrature processed using Doppler techniques. Connected to the antenna (10) is a transceiver (12) that includes a quadrature mixer (48) coupled to an RF oscillator (50) through an RF switch (52). The RF switch (52) is controlled by a switch driver (54) to provide pulse energy from the antenna (10). Doppler outputs E.sub.1 and E.sub.2 from transceiver (12) are processed in the same manner except for a 90-degree phase lead applied to the Doppler output E.sub.2 by a phase lead network (18). Doppler outputs E.sub.1 and E.sub.2 (E.sub.2 90-degree phase shifted) are applied simultaneously to a sum and signature processor (24) and to a difference and signature processor (22). The sum and signature processor provides the "approach" receiving signal and processes the signature to further reduce the nuisance alarm rates. The difference and signature processor (22) provides the "recede" receiving signal and similarly processes the signature to reduce nuisance alarms. Outputs of the processors (22) and (24) are respectively applied to rectifiers (32) and (28) and to integrators (34) and (30) which are similar in design and serve to rectify, amplify and filter the inputs applied thereto. A voltage comparator (36) responds to the output of the integrators (34) and (30) to trigger an alarm (38) when the voltage difference between the outputs of the integrators reaches a predetermined magnitude.

Dependencies are inferred from the claim text.