Memory-saving all channel digital tuning system

Abstract

A tuning system for a television receiver includes fine tune memories and tuning information memories having reference channel nominal tuning information for each frequency band and increment tuning information representing the tuning voltage differences between successive channels. Accumulator means add the reference channel tuning information and increment information to develop the nominal tuning voltage for any selected channel. Control logic, including channel number counters and latches and state counters, is coupled to the accumulator means, tuning information memories and the fine tune memories. The memories' and accumulator means' outputs are coupled to a corresponding plurality of comparators which are also coupled to counters for deriving pulse-width modulated (PWM) signals corresponding to tuning information in the accumulator means and memories. The PWM signals are supplied to a tuning voltage generator where they are combined to produce the final tuning voltage for the tuner. The increment tuning information is representative of the slope of the tuning curve at each of the channel tuning points and is used to equalize any auxiliary tuning voltage source. The final tuning voltage consists of the derived nominal tuning voltage combined with the product of the fine tune voltage and channel increment tuning information.