Traffic radar and apparatus therefor
First Claim
1. Apparatus for synthesizing the frequency of an unknown periodic input signal which may be accompanied by noise comprising source means providing a periodic signal of variable frequency adapted for locked operation at a sample frequency which is a predetermined multiple of said input signal, first sample means responsive to said source means for providing a first sample of said input signal for a known time interval less than one half of the period of said input signal, control means generating a control signal having a level related to the magnitude and polarity of said first sample for relatively rapidly altering the frequency of said source means in response to said control signal, second sample means responsive to said source means for providing a second sample of said input signal for a predetermined time interval less than one half of the period of said input signal, sweep means generating a sweep signal which relatively slowly alters the frequency of said source means, and means responsive to an output of said second sample means to disable said sweep means when said output of said second sample means has a predetermined polarity.
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Accused Products
Abstract
Apparatus is provided for determining the frequency of unknown periodic input signals and primarily generally sinusoidal signals which may be accompanied by substantial noise. More particularly a unique traffic radar or doppler radar is provided employing such frequency measuring apparatus. The apparatus includes a phase locked loop in which a frequency multiplier effect is produced and in which a frequency 12 times the periodic input signal being subjected to measurement is employed for taking two independent samples of the input signal and providing a synthetic representation of that signal. The two samples are centered about quadrature time references and are preferably conterminous. This signal can be measured and utilized for speed measuring purposes and other purposes where the accurate measurement of a periodic signal accompanied by noise is desired. The system includes two sampling gates to control the frequency of a variable controlled oscillator in a manner which accurately matches the oscillator output to a harmonic of the input and selects portions thereof to eliminate harmonic ambiguities. Circuit means is also provided for signal verification and for improved long-term noise rejection by utilizing variable time constants.
26 Citations
19 Claims
- 1. Apparatus for synthesizing the frequency of an unknown periodic input signal which may be accompanied by noise comprising source means providing a periodic signal of variable frequency adapted for locked operation at a sample frequency which is a predetermined multiple of said input signal, first sample means responsive to said source means for providing a first sample of said input signal for a known time interval less than one half of the period of said input signal, control means generating a control signal having a level related to the magnitude and polarity of said first sample for relatively rapidly altering the frequency of said source means in response to said control signal, second sample means responsive to said source means for providing a second sample of said input signal for a predetermined time interval less than one half of the period of said input signal, sweep means generating a sweep signal which relatively slowly alters the frequency of said source means, and means responsive to an output of said second sample means to disable said sweep means when said output of said second sample means has a predetermined polarity.
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9. In doppler radar apparatus for determining the speed of a vehicle the combination comprising:
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input means for providing an input signal having a frequency related to the speed of such vehicle, source means for generating a synthetic signal of variable controllable frequency, gate means receiving said input signal, control means energized from said gate means and controlling the frequency of said source means, sampling means controlled by said source means to control said gate means whereby said gate means applies said input signal to said control means for intermittent periods with a duty cycle less than 50% to equate the periodicity of said synthetic signal to the periodicity of said input signal and eliminate harmonic ambiguities of said input signal, digital counter and display means energized from said source means to generate a count related to the frequency of said source means, and a timer means controlling the counting interval of said digital counter and display means whereby said count during said interval represents the speed of such vehicle. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification