Elimination of spurious signals in double conversion tuner using a dynamic intermediate frequency and a preselected crystal reference frequency

摘要

A double conversion tuner (DCT) free of spurious signals generated by the local oscillator frequencies and the crystal reference frequency is described herein. These spurious signals are generated by the first and/or second oscillator signals as well as by their harmonic frequencies. Spurious signals are also generated when the crystal reference frequency is not properly selected. In the past, complex-mechanical designs had to be used to isolate circuit blocks to reduce these spurious signals. By using a dynamic first intermediate frequency and/or selecting the value of the crystal reference frequency, these spurious signals can be reduced or eliminated.