Detection system employing digital bandpass filtering circuitry

Claim 2

A detection system for detecting motion of a particular character in a predetermined space, said system comprising: a continuous wave transmitter for sending a wave of energy of predetermined frequency through the space wherein motion is to be detected; a receiver arranged to receive said wave of energy as modified by the motion of objects within said space; a phase rate detector, operably coupled with said transmitter and receiver, for comparing the instantaneous phase of the received wave with that of the transmitted wave and for providing a digital output signal comprising a train of pulses having pulse widths proportional to the rate at which the phase of said received wave changes with respect to said transmitted wave; and digital filtering means, operably connected with said phase rate detector output, for filtering out pulse widths uncharacteristic of the particular motion to be detected.

Claim 3

A detection system according to claim 1 wherein said digital filtering means comprises high and low-pass filters connected in series.

Claim 4

A detection system according to claim 2 wherein said low-pass filter is fed by said phase rate detector output and comprises means for transmitting only those pulses having a width greater than a predetermined value, and said high-pass filter is fed by pulses transmitted by said low-pass filter and comprises means for counting the number of pulses transmitted by said low-pass filter and for providing an output signal by which an alarm may be activated when said counting means counts more than a predetermined number of pulses within a predetermined time interval.

Claim 5

A detection system according to claim 1 wherein said phase rate detector comprises: means, operably coupled with said transmitter and receiver, for comparing the instantaneous phase of said received and said transmitted wave and for providing a digital output signal comprising a train of pulses, each of said pulses having a pulse width proportional to the instantaneous difference in phase between said transmitted and received waves; means for averaging said digital output of said phase comparing means so as to obtain an analog signal having a frequency substantially equal to the rate at which the phase of said received wave changes with respect to that of said transmitted wave; and means for converting said analog signal to a digital waveform comprising a train of pulses, each pulse of which has a pulse width proportional to the rate of change in phase.

Claim 6

The detection system according to claim 4 wherein said analog to digital converting means comprises a regenerative squaring circuit of the Schmitt trigger variety.

Claim 7

A detection system for detecting motion of a predetermined character in a predetermined space said system comprising: means for transmitting a continuous wave of energy of predetermined frequency through the space wherein motion is to be detected; means for receiving said energy wave as modified by the motion of objects within said space; a phase rate detector, operably coupled with said transmitting and receiving means for comparing the instantaneous phase of the received wave with that of the transmitted wave and for providing a digital output signal comprising a train of substantially rectangular pulses having a repetition rate corresponding to the rate at which the phase of thE received wave changes with respect to the transmitted wave, said phase rate detector comprising gate means, operably coupled with the outputs of said transmitting and receiving means, for transmitting pulses having pulse widths proportional to the instantaneous difference in phase between said transmitted and received waves, means for averaging the output of said gate means so as to provide an analog waveform having a frequency proportional to the rate at which the phase of said received wave varies with respect to said transmitted wave, and means for squaring said analog waveform so as to provide said digital output signal; and digital filtering means, operably connected with said phase rate detector output, for filtering out pulse widths uncharacteristic of the particular motion to be detected.

Claim 8

A detection system for detecting motion of a predetermined character in a predetermined space said system comprising: means for transmitting a continuous wave of energy of predetermined frequency through the space wherein motion is to be detected; means for receiving said energy wave as modified by the motion of objects within said space; a phase rate detector, operably coupled with said transmitting and receiving means for comparing the instantaneous phase of the received wave with that of the transmitted wave and for providing a digital output signal comprising a train of substantially rectangular pulses having a repetition rate corresponding to the rate at which the phase of thE received wave changes with respect to the transmitted wave, said phase rate detector comprising gate means, operably coupled with the outputs of said transmitting and receiving means, for transmitting pulses having pulse widths proportional to the instantaneous difference in phase between said transmitted and received waves, means for averaging the output of said gate means so as to provide an analog waveform having a frequency proportional to the rate at which the phase of said received wave varies with respect to said transmitted wave, and means for squaring said analog waveform so as to provide said digital output signal; and digital filtering means, operably connected with said phase rate detector output, for filtering out pulse widths uncharacteristic of the particular motion to be detected.

Claim 9

A Doppler detection system for detecting motion of a particular character occurring in a predefined space, said system comprising: means for transmitting a continuous wave of energy of predefined frequency into said predefined space; transducing means arranged to receive said wave of energy upon being reflected and/or modified by objects within said predefined space, said transducing means being adapted to provide a first electrical signal having a frequency proportional to the frequency of the received wave of energy; means for providing a second electrical signal having a frequency proportional to the frequency of said transmitted wave of energy; means for comparing said first and second electrical signals to provide an analog signal of the Doppler frequency; means, operatively coupled with said analog signal, for providing a digital output signal comprising a train of pulses, each pulse having a pulse-width proportional to the instantaneous Doppler frequency; and digital filtering means for transmitting only those pulses in said train of pulses having pulse widths within a predefined range of pulse widths.

Claim 10

A Doppler detection system for detecting motion of a particular character occurring in a predefined space, said system comprising: means for transmitting a continuous wave of energy of predefined frequency into said predefined space; transducing means arranged to receive said wave of energy upon being reflected and/or modified by objects within said predefined space, said transducing means being adapted to provide a first electrical signal having a frequency proportional to the frequency of the received wave of energy; means for providing a second electrical signal having a frequency proportional to the frequency of said transmitted wave of energy; means for comparing said first and second electrical signals to provide an analog signal of the Doppler frequency; means, operatively coupled with said analog signal, for providing a digital output signal comprising a train of pulses, each pulse having a pulse-width proportional to the instantaneous Doppler frequency; and digital filtering means for transmitting only those pulses in said train of pulses having pulse widths within a predefined range of pulse widths.

Claim 11

The invention according to claim 7 wherein said wave of energy is acoustic in nature and said predefined frequency is ultrasonic.

Claim 12

The invention according to claim 7 wherein said digital filter comprises low-pass filtering means for transmitting only those pulses having a pulse width greater than a predefined value and means operatively coupled to said low-pass filtering means for counting the number of pulses transmitted by said low-pass filtering means and for providing an output signal, whereby an alarm can be activated, when said counting means counts more than a predetermined number of pulses within a predefined time interval.

Claim 13

The invention according to claim 7 wherein said squaring means comprises a Schmitt-type trigger.