| 摘要 |
<p>PURPOSE:To improve the S/N for weak electric field to make an AGC circuit of the IF band unnecessary by changing the passing band width and the degree of amplification for IF in proportion to and in inverse proportion to the reception electric field. CONSTITUTION:The output of a resonance circuit Q which has a resonance point in the center frequency of IF is amplified by an amplifier A of fixed gain, and an output voltage V0 is obtained through a forward voltage control amplifier beta'. This voltage V0 is fed back negatively to the input side of the resonance circuit Q through a feedback circuit beta. In this case, the feedback rate of the feedback circuit beta is changed in accordance with the reception electric field. The passing band width for IF is changed in proportion to the reception electric field, and the degree of amplification is changed in inverse proportion to the reception electric field. Thus, the AGC function is obtained.</p> |
