Rapid scanning radio with multi-mode local oscillator control

Claim 1

A rapid scanning radio circuit with multi-mode local oscillator control, comprising: an electrically variable local oscillator having a frequency control input; a reference oscillator; synthesizer means for comparing an output signal from said local oscillator with an output signal from said reference oscillator, said synthesizer means including a frequency code input; filter means for filtering an output signal from said synthesizer means; a DAC; switch means for coupling said local oscillator frequency control input to said filter means in a closed-loop mode and to said DAC in an open-loop mode; first scan means operative during said closed-loop mode for sequentially supplying a plurality of frequency codes to said frequency code input of said synthesizer means, said scan means supplying each frequency code for a sufficient duration for the signal on said oscillator frequency control input to reach a steady state; processor means operative during said closed-loop mode for determining a DAC input value which corresponds to the steady-state level of the signal on said oscillator frequency control input; and second scan means operative during said open-loop mode for sequentially loading said DAC with said DAC input values identified by said processor means.