SSB filter suitable for IF section of radio receiver - uses combined quartz crystal and ceramic oscillator bridge circuits to regulate characteristics

摘要

The SSB filter has a quartz crystal and a ceramic oscillator. The latter is in a bridge circuit. Two such combinations of crystal and ceramic oscillator may be combined. Tuning components, e.g. variable capacitors are used to set the frequency of the quartz crystal. One branch of the bridge circuit is made up from the series combination of the ceramic oscillator, a capacitor and an inductor while another branch is formed from a capacitor. The resulting composite characteristics of the filter have steep edges between passband and stop band and constant impedance within pass and stop bands.