Gte Government Systems Corporation

Gte Communication Products Corporation

Mark R Magee

G Kirby Miller

Richard E Saffran

Richard D James

Melvin E Trimble

Drift of the standing wave pattern in an acoustic doppler intrusion detection system in a confined space is compensated by adjusting the relative radiating and receiving positions of the radiator and receiver transducers, respectively, either mechanically or electrically until the signal level of the carrier wave at the receiver transducer is optimized. In the mechanical adjustment mode, either the receiver transducer or the radiating transducer is supported for movement relative to the other and is moved by a motor energized under the control of a signal level sensor circuit connected to the output of the receiver transducer. In another mode, a plurality of receiver (or alternatively radiator) transducers are connected through a switch to the signal level sensor circuit which in response to a drop in received signal level below a predetermined threshold, selectively switches the active transducer to optimize the received signal level. In still another mode, one of at least two radiator (or alternatively, receiver) transducers is connected through a variable phase shifter to the signal generator (or to the receiver circuit for the receiver transducer), the phase shifter being adjustable in response to the output of the signal level sensor to optimize the signal level at the receiver transducer. The invention comprehends the apparatus for and method of optimizing signal strength at the receiver transducer.

Apparatus for and method of doppler motion detection with standing wave

A multimode perimeter intrusion detection system comprises at least one elongated electret tape mounted on a barrier, such as a fence or wall, along the perimeter of an area to be protected and operated simultaneously in both active and passive modes to detect intruders in proximity to, as well as in contact with, the barrier. The tape is directly mechanically coupled to the barrier above and parallel to the ground or floor and is electrically connected to a sound wave generator and to signal processing apparatus which detects signals produced on the tape by intruders and activates an alarm. In the active mode, the tape radiates sound waves, preferably in the ultrasonic range, outwardly from the barrier and receives doppler-shifted reflections from a person moving in the sound field for transmission to the signal processing apparatus. In the passive mode, the tape senses vibrations in the barrier caused by contact with the intruder, converts the vibrations to signals and transmits the latter to the signal processing apparatus. In a second passive mode, the tape also acts simultaneously as a line microphone to pick up audio sounds and to transmit them to a loudspeaker at the monitoring station. In a preferred form of the invention two of such tapes are mounted in juxtaposition and coextensively on the barrier, one tape functioning as the ultrasonic wave radiator, the other tape being the receiver-connected transducer.

Multimode perimeter intrusion detection system

Drift of the standing wave pattern in an acoustic doppler intrusion detection system with radiating and receiving transducers in a confined space is compensated by changing the operating frequency of the carrier wave generator when the magnitude of the received carrier wave is less than a predetermined threshold level. The magnitude of the received carrier wave is continuously monitored and compared to the threshold level. The generator frequency is incrementally increased until the carrier wave magnitude is optimum. This invention comprehends the apparatus for and method of optimizing signal strength at the receiving transducer by this technique.

Apparatus for continuously making an electret tape having an electrically conductive strip with dielectric layers on opposite sides thereof in which the tape is moved vertically in the direction of its length. A pair of opposed electrodes connected to a high voltage source and continuously wetted with a dielectric fluid contact the respective dielectric layers to electrostatically charge each layer. A second pair of identical electrodes connected to the high voltage source and the dielectric fluid supply is spaced above the other electrode pair and repeats electrostatic charging of the dielectric layers to insure uniformity of charge thereon. Fluid on the layers is dried by air blown against them as the tape emerges from the second electrode pair.

Apparatus for and method of making an electret tape

Apparatus for making an electret tape having an electrically conductive strip with a dielectric layer on one side thereof comprises tape supply and take-up reels arranged to move the tape from the former to the latter in an upwardly inclined plane and an electrostatic charging assembly between the reels having a dielectric fluid applicator for applying the fluid directly to the dielectric layer, a sponge-like electrode connected to a high dc voltage source, and an air blower for drying the fluid on the tape. The electrode is longitudinally spaced from the fluid application point in the direction of tape movement, engages the dielectric layer across its full width, and is wetted on the tape input side by the fluid on the layer. The blower is on the tape output side of the electrode with a baffle spaced closely to the dielectric layer between the blower and the electrode. This arrangement insures that the electrode is continuously wet and that the fluid is dried on the dielectric layer before the latter moves away from the electrode.

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Saratoga, CA, United States of America

Mark R Magee