Frequency bandwidth tuning system and method

Claim 1

A clocked receiving system including a receiver having a controllable oscillator and capable of automatically sensing the frequency at a prespecified position within the bandwidth of a received input signal of frequency unknown at the receiving system, said receiver producing pulses at a difference frequency between said oscillator and said received signal, comprising clock means for providing a series of clock pulses at a given rate, clock rate division means responsive to said clock means for providing clock pulses at a reduced rate which is less than said given rate by an amount dependent upon said prespecified position, oscillator frequency control means including a first up-down counter responsive to pulses from said clock means for incrementally controlling the oscillator tuning frequency of said receiver over the bandwidth of said receiver as a function of the count of said first counter to effect an incremental scanning of the oscillator frequency back and forth over a range of discrete frequency increments during the operation of said clock means, measuring counter means including a second up-down counter responding to the presence of difference frequency pulses and to the output of said clock rate division means for counting up at said reduced rate during the presence of said pulses from an initial count up to a threshold count attained at occurrence of a difference frequency pulse corresponding to the maximum bandwidth of said received input signal, said measuring counter means including a control circuit responsive to cessation of said difference frequency pulses for changing the direction of counting of said first and second counters and for changing the counting rate of said second counter to that of said clock means, and clock inhibiting means responding to attainment of the initial count by the down-counting second counter for maintaining the incremental frequency count of said first counter and to hold the receiver at said predetermined position within the bandwidth of said received input signal.