A Microprocessor-Based TV Frequency Synthesizer with Automatic Fine Tuning

Digital tuning systems are continually becoming more and more sophisticated. In addition to this TV manufacturers can have widely varying require ments. To meet these demands a microprocessor based digital tuning system has been developed, thus allowing the maximum flexibility in system designs. Both voltage and frequency synthesis can be easily implemented. In the frequency synthesis configuration the system allows automatic search through the bands and direct channel selection with automatic search inside the channel for transmitters operating off assigned frequencies. The frequency is synthesized with a resolution of 500KHz and a digital plus linear Automatic Fine Tuning is provided in order to reach the correct tuning position and to control transmitter drifts.