초록 ▼

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 th

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.

대표청구항 ▼

Apparatus for detecting motion of an object in a confined space to the degree that said object amplitude modulates a carrier wave in a predetermined frequency range, said apparatus comprising: means for generating the carrier wave; radiator means connected to said generating means and positioned to

Apparatus for detecting motion of an object in a confined space to the degree that said object amplitude modulates a carrier wave in a predetermined frequency range, said apparatus comprising: means for generating the carrier wave; radiator means connected to said generating means and positioned to radiate the carrier wave into said space; receiving means spaced from said radiator means and positioned in said space to receive said carrier wave; demodulator means connected to the output of said receiver means for demodulating said carrier wave and for producing an alarm in response to movement of an object in said space; and means to change the effective position of said radiator means or said receiver means, in response to a decrease in the strength of the carrier wave at said receiver means below a predetermined level.