ELIMINATION OF SPURIOUS SIGNALS IN A DOUBLE CONVERSION TUNERUSING A DYNAMIC INTERMEDIATE FREQUENCY AND A PRESELECTED CRYSTAL REFERENCE FREQUENCY

摘要

A double conversion tuner (DCT) free of spurious signals generated by t he local oscillator frequencies and the crystal reference frequency is describe d 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 generate d when the crystal reference frequency is not properly selected. In the past, complex mechanical designs had to be used to isolate circuit blocks to reduc e these spurious signals. By using a dynamic first intermediate frequency and/ or selecting the value of the crystal reference frequency, these spurious signa ls can be reduced or eliminated.