Surface wave filter with variable characteristics, for TV receiver IF stage, provides flat bandpass region with steep sides or step in LF-side skirt response and Nyquist characteristic

摘要

The SAW filter has selectable characteristics, acting as a simple bandpass filter with minimal attenuation between 32.25 and 40.05 MHz and a steep skirt response, or with a narrower passband exhibiting a Nyquist characteristic and a step in the skirt response on the LF side at - 20 dB. The first response is used for reception of digital signals and the second for analog signals, the step in the LF filter skirt response acting as a sound shelf. Independent claims are included for : (1) a circuit for receiving modulated HF signals; and (2) a TV receiver using the SAW filter of the invention.