Abstract The invention relates to an improvement in direction sensitive ultrasonic Doppler detecting devices wherein an ultrasonic transducer transmits a given freqency signal toward an object which in turn reflects the given signal and Doppler shifted signals based on the movement of the object. The reflected signals including the Doppler shifted signals are processed and evaluated to determine the characteristics of the object movement both as to direction and degree. The insertion of a differentiating circuit in the processing of the reflected signals minimizes false interpretation of the reflected signals caused by non-harmonic oscillatory movement of the object. Furthermore through the addition of a signal processing circuit utilizing a non-linear multiplier circuit for multiplying the instantaneous values of the components of the reflected signals in contrast to the linear multiplication of these signals, the loss of sensitivity of the Doppler detection device as a function of distance is represented as as in the case in the conventional coherent Doppler detection devices.
In a Doppler-type system for detecting movement of an object, the combination of, transmitting means for transmitting an AC signal at a certain frequency, receiving means positioned at a distance X from the object for receiving the reflected portion of said AC signal from the object, first mixing means for deriving a Doppler signal which is the difference in frequency between the transmitted and received AC signals, first phase shifting means for phase shifting the transmitted signal a predetermined amount, second mixing means for deriving a Doppler signal which is a difference in frequency between the phase shifted transmitted AC signal and the received AC signal, second phase shifting means for shifting the phase of the AC output signal of said second mixing means, means operatively connected to the output of said first mixing means for converting said AC output signal from said first mixing means into a psuedo rectangular output waveform of substantially constant amplitude, a non-linear correlating means operatively coupled to the outputs of said means for converting and said second mixing means for producing an output signal having a magnitude which is proportional to 1/X and is indicative of the relative movement of the object.
Claim 2
Dependent Claim
198 words
In a Doppler-type system for detecting movement of an object, the combination of, transmitting means for transmitting an AC signal at a certain frequency, receiving means positioned at a distance X from the object for receiving the reflected portion of said AC signal from the object, first mixing means for deriving a Doppler signal which is the difference in frequency between the transmitted and received AC signals, first phase shifting means for phase shifting the transmitted signal a predetermined amount, second mixing means for deriving a Doppler signal which is a difference in frequency between the phase shifted transmitted AC signal and the received AC signal, second phase shifting means for shifting the phase of the AC output signal of said second mixing means, means operatively connected to the output of said first mixing means for converting said AC output signal from said first mixing means into a psuedo rectangular output waveform of substantially constant amplitude, a non-linear correlating means operatively coupled to the outputs of said means for converting and said second mixing means for producing an output signal having a magnitude which is proportional to 1/X and is indicative of the relative movement of the object.
Claim 3
Dependent Claim
18 words
A Doppler-type system as claimed in claim 1 wherein said second phase shifting means comprises a differentiating means.
Claim 4
Dependent Claim
38 words
In a Doppler-type system as claimed in claim 2 wherein said non-linear correlating means includes a multiplier means for multiplying said psuedo rectangular output waveform of said amplifying and clipping means and the output of said differentiating means.
Claim 5
Dependent Claim
22 words
In a Doppler-type system as claimed in claim 1 wherein said means for converting comprises a signal amplifier and signal clipper means.