| 摘要 |
<p>The signal of desired frequency band and the signal of frequency band of interference wave are input to a gain variable circuit from a terminal and is then supplied to an active filter circuit after the gain control. Such output signal is waveform-shaped by a limiter circuit and is then supplied to a signal data demodulating circuit from the terminal. A first coefficient circuit multiplies the predetermined coefficient to the level of an output signal of the active filter circuit, a second coefficient circuit multiplies the predetermined coefficient to the input signal level, a first level detecting circuit and a second level detecting circuit detect output levels of the first and second coefficient circuits. Moreover, a switch circuit controllably outputs the higher level signal of the detecting signals of the first and second level detecting circuits and its output is input to a comparator (differential amplifier) and is then compared with an output of the reference signal source to provide the stable output characteristic of the active filter circuit through the feedback control. <IMAGE></p> |
