Method for tuning radio and television receivers with a microprocessor-controlled PLL circuit

摘要

Tuning system for radio and television receivers which have a microprocessor-controlled PLL circuit for generating a tuning voltage for the capacitance diodes in the RF and oscillator circuits. The step length of the tuning, which is determined by the PLL system, is reduced by inserting intermediate steps which are produced by digitally adding a capacitance with the aid of a control bit supplied by the microprocessor, which shifts the IF response curve.