DE2331328

• Main Authors: GERSHBERG, DAVID NELSON, ROCKVILLE, MD., US, LEE, ALEX YOUNG, ARLINGTON, VA., US
• Format: Patent
• Language: English
• Published: 23.06.1988
• Edition: 4
• Subjects: ALARM SYSTEMS; ANALOGOUS ARRANGEMENTS USING OTHER WAVES; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION ORRERADIATION OF RADIO WAVES; MEASURING; ORDER TELEGRAPHS; PHYSICS; RADIO DIRECTION-FINDING; RADIO NAVIGATION; SIGNALLING; SIGNALLING OR CALLING SYSTEMS; TESTING

Motion within a large specified volume is detected by multiple ultrasonic transducer assemblies with a redundant microwave antenna to reduce false alarms. Each of the ultrasonic transducer assemblies contains a plurality of highly directive transmitting radiating elements and/or a plurality of highly directive receiving elements. Combining networks interconnect the various radiating elements in parallel to a frequency source. The microwave transducer includes a transmit/receive antenna coupled to a microstrip oscillator through a microstrip balanced mixer. Signals from the ultrasonic transducers are processed by means of time integration to provide an alarm signal. Similarly, signals received at the microwave antenna are processed by means of time integration to provide an alarm signal. Alarm signals from both the ultrasonic subsystem and the microwave subsystem are combined in logic that responds to generate a system alarm only upon the simultaneous existence of alarm signals from both sources. Also coupled to the ultrasonic subsystem and the microwave subsystem is an automatic self-testing and tamper determining system. When either transducer source indicates a fault condition, an alarm signal is generated by combining logic networks.