Patent ID: 6188349
Filing Date: 2001-02-13
Classification: F41G,G01S

Abstract:
In a radar receiver wherein a voltage controlled oscillator is used to produce a local oscillator signal to be heterodyned with a radar signal to form an intermediate frequency signal for detection in a phase detector, such detector producing a first alternating signal having a frequency indicative of the difference between the actual frequency of the voltage controlled oscillator and the frequency of such oscillator required to produce the intermediate frequency signal, the improvement comprising:(a) a high pass filter, responsive to the alternating signal from the phase detector, for isolating such signal;(b) means, responsive to the local oscillator signal out of the voltage controlled oscillator, for producing a second alternating signal indicative of the difference between the actual frequency out of the voltage controlled oscillator and a reference frequency; and(c) means, responsive to the first and second alternating signals, for changing the frequency of the voltage controlled oscillator to null the first alternating signal.