| 摘要 |
PURPOSE:To accomplish an excellent demodulating characteristic against variance in input frequency and temperature, by inserting a SAW filter having the same delay time and temperature characteristics to a Nyquist filter side and a limiter circuit side respectively. CONSTITUTION:An input signal from an input terminal IN is amplified to a specified level at an intermediate frequency amplifier AMP and distributed at a hybrid HYB. One signal distributed is fed to a video detection circuit DET via a Nyquist filter SAW1 by a SAW filter. Further, another signal is picked up for a video carrier at a limiter LIM through a video carrying filter FvBPF, and this is fed to the circuit DET via a band pass filter SAW2 consisting of SAW filters. In this case, by manufacturing the filters SAW1 and SAW2 on the same board, the temperature characteristics are entirely the same and negligible. Further, the filters SAW1 and SAW2 are designed to have the same delay time easily. |
