Traffic radar and apparatus therefor

Abstract

Apparatus is provided for determining the frequency of unknown periodic input signals and primarily generally sinusoidal signals which may be accompanied by very substantial noise. More particularly, the system for determining the frequency of unknown periodic input signals accompanied by substantial noise is adapted to a unique traffic radar or doppler radar system. The apparatus includes a phase locked loop in which the incoming signal accompanied by noise is compared with the output from a voltage controlled oscillator to generate a synthetic signal which is substantially free of noise and is well adapted for counting, measuring and display circuitry to give a direct indication of the input signal frequency or a parameter directly related to that input signal frequency. Specifically in doppler radar systems the direct readout is in "miles per hour", a direct function of doppler frequency. The signal which is being subjected to frequency determination is applied directly to the comparator portion of the phase locked loop circuit and it is also applied to the comparator portion of the phase locked loop circuit through a tunable band pass filter whereby speed of response is obtained without loss of noise rejection or frequency or harmonic range. Also an automatic frequency control loop is employed with the comparator to adjust the voltage control oscillator and this AFC loop has adjustable gain which is directly related to the frequency of the incoming signal to enhance the stability over the entire frequency range. The system is also capable of an instantaneous determination of locked operation whereby false readings are avoided.

Dependencies are inferred from the claim text.