Abstract: In a radar or radio frequency signal regenerator an incoming RF signal is mixed with the output of a single-side-band generator to produce a derived IF signal. The single-side-band generator operates to mix together the outputs of two local oscillators to provide the signal mixed with the incoming RF signal. A frequency lock loop circuit is used to compare the frequency of the derived IF signal with a reference IF frequency and the frequency of one of the local oscillators is varied to correct any frequency error and thus to make the frequency of that local oscillator equal to the incoming RF frequency.

Abstract: In radar apparatus for actively enhancing and retransmitting a received radar signal, the incoming signal is mixed with the output of a first local oscillator, the resulting signal being supplied to a frequency lock loop which varies the frequency of the first local oscillator until the frequency of the resulting IF signal is equal to a first reference IF frequency. The first local oscillator output is mixed with the output of a second local oscillator, the frequency of which is varied until the frequency of the resulting second IF signal is equal to a second reference IF frequency. The output from the second local oscillator is retransmitted. The first and second reference IF frequencies are identical if the frequency to be retransmitted is the same as the incoming RF carrier frequency.

Abstract: A frequency lock loop circuit has a pair of square-wave pulse generators which are clocked from a common input. The width of the pulses from the first generator is dependent on the frequency of the clocking signal; the width of the pulses from the second generator is dependent on a reference frequency. The difference in the width of the pulses from the two generators is fed back as an error signal to adjust the frequency of the clocking signal until the two waveforms are aligned. In a heterodyne receiver, the clocking signal may be the intermediate frequency signal from the mixer and it may then be adjusted by adjusting the frequency of the local oscillator in accordance with the pulse-width difference signal.