Importance

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Abstract

The present invention provides a broad band, multi-band radar detector which may be configured so as to have two or three down conversion stages. There are three mixers in the circuit, the second of which has a frequency synthesized local oscillator which is governed by a phase lock loop feedback circuit under the control of a microprocessor, so that the output frequency of the second local oscillator may be varied by an amount equal to .+-.f.sub.adj. The first local oscillator is also under the control of the microprocessor, so that a specific intermediate frequency signal from the first mixer may be derived. By varying the frequency of the second frequency synthesized local oscillator, the tuning range of the radar detector may be increased in each frequency band of interest by an amount equal to .+-.f.sub.adj for all frequency values in each respective frequency band of interest. The radar detector is a self-calibrating detector, so that the output frequency from the first swept local oscillator may be accurately controlled by determining the specific tuning voltage for a specific first local oscillator frequency at which a particular incoming radar signal may be detected. This is accomplished by bypassing the second mixer, and controlling its output frequency so that an harmonic frequency will mix with the first local oscillator frequency to give a calibration response for any predetermined input radar frequency. Accordingly, the problem of drift of the tuning capability of the radar detector may be accurately controlled.

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First Claim