Abstract: An ultrasonic intrusion detection system having means for transmitting and receiving ultrasonic energy within a protected zone and generating an alarm when a moving object is present in the protected zone is supplemented to provide multiple independent response zones utilizing the same transmitter for all zones but individual receiver modules which can be added to the existing transmitter-receiver system to provide protection for additional independent zones with associated indicators for selectively indicating those zones which have been triggered by the presence of an intruder or other moving object.

Abstract: A transducer assembly which generates a cone shaped radiation pattern concentric with a selected axis is formed by a piezoelectric element mounted in a cylindrical resonant cavity defined by a Helmholtz chamber. Circumferentially spaced apart and radially aligned circular apertures are formed in the chamber's cylindrical side wall and an inclined reflecting plate is spaced apart from the apertures a selected distance. The plate extends outwardly from the chamber at an angle of less than 90.degree. to the chamber axis. The cone shaped radiation pattern is produced by generating a plurality of discrete spherical radiation patterns, combining these patterns to form an annular radiation pattern and partially reflecting the annular radiation pattern from an inclined reflection plate extending at an angle to the chamber axis of less than 90.degree. to produce a cone shaped radiation pattern.

Abstract: An ultrasonic or microwave intrusion detection system uses a transmitter having one or more transducers or antennas for maintaining wave fields in the area to be protected and fed by one or more transducers or antennas which detects echo reflections of the energy from within the area. The receiver employs two mixers energized to be mixed with the echo signals and a portion of the energy from the transmitter, one of the mixers receiving such transmitter energy with 90.degree. phase shift relative to the other mixer. The outputs of the two mixers thus are in quadrature phase relative to each other and define a rotating vector which contains the information relating to the echo signals. The product of these quadrature signals obtained by multiplying them together is processed continuously to obtain target information in the presence of substantially larger clutter return signals and other interference.