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US 3,942,178 AGranted
Intrusion detection system
AssigneeSontrix, Inc.
InventorKenneth R. Hackett
Life of this patent
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AssigneeSontrix, Inc.
InventorKenneth R. Hackett
Estimating the term…
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. The multiplication of the two quadrature signals to obtain cancellation of the clutter return signals and enhancement of the target signals is achieved without further phase shift requirements by differentiating one of the quadrature signals before it is multiplied with the other quadrature signal. In the preferred embodiment the differentiated quadrature signal is normalized to enhance the dynamic range of the equipment and eliminate the requirement for balanced channels.
The method of detecting moving target echos in the presence of interference comprising the steps of radiating energy and receiving echo return energy, hetrodyning radiated and received energy signals to produce separate quadrature beat frequency signals, differentiating and amplitude limiting one of said beat frequency signals, multiplying the differentiated and limited signal and the other beat frequency signal to obtain the four quadrant product of the signals multiplied, and integrating said product.
In an echo signal intrusion alarm system having enhanced detection capability for moving objects in the presence of interference and clutter return echos wherein a signal is transmitted into a protected zone and reflected signals are received from said zone, said system including first and second quadrature mixing means for mixing signals corresponding to the transmitted and received signals to produce direction sensitive quadrature output signals in accordance with the beat frequency between said transmitted and received signals, the improvement comprising phase rotation processor means responsive to the full information content of a predetermined bandwidth of said quadrature output signals for producing a bipolar signal in accordance with the product of the magnitudes of said quadrature output signals multiplied by said beat frequency, means for integrating said bipolar signal, and threshold means responsive to the magnitude of the integrated bipolar signal exceeding a predetermined value for providing an alarm signal.
In an echo signal intrusion alarm system having enhanced detection capability for return echos from a moving object in the presence of interference and clutter return wherein a signal is transmitted into a protected zone and reflected signals are received from said zone, said system including first and second quadrature mixing means for mixing signals corresponding to the transmitted and received signals to produce direction sensitive quadrature output signals in accordance with the beat frequency between said transmitted and received signals, the improvement comprising:
In an echo signal intrusion alarm system having enhanced detection capability for return echos from a moving object in the presence of interference and clutter return wherein a signal is transmitted into a protected zone and reflected signals are received from said zone, said system including first and second quadrature mixing means for mixing signals corresponding to the transmitted and received signals to produce direction sensitive quadrature output signals in accordance with the beat frequency between said transmitted and received signals, the improvement comprising:
In an echo signal intrusion alarm system having enhanced detection capability for return echos from a moving object in the presence of interference and clutter return wherein a signal is transmitted into a protected zone and reflected signals are received from said zone, said system including first and second quadrature mixing means for mixing signals corresponding to the transmitted and received signals to produce direction sensitive quadrature output signals in accordance with the beat frequency between said transmitted and received signals, the improvement comprising:
In an echo signal intrusion alarm system having enhanced detection capability for return echos from a moving object in the presence of interference and clutter return wherein a signal is transmitted into a protected zone and reflected signals are received from said zone, said system including first and second quadrature mixing means for mixing signals corresponding to the transmitted and received signals to produce direction sensitive quadrature output signals in accordance with the beat frequency between said transmitted and received signals, the improvement comprising:
Dependencies are inferred from the claim text.