| 摘要 |
PURPOSE:To decrease a nonlinear distortion at a strong electric field while ensuring a sufficient S/N at a weak electric field by adding a strong electric field detecting circuit so as to decrease the gain of a high frequency amplifier section at a strong electric field. CONSTITUTION:A strong electric field detection circuit 10 detects a strong electric field based on the reduction in an output voltage of an RF.AGC delay circuit 5. Then a detection circuit 10 detecting the strong electric field increases an output voltage of an RF.AGC delay adjusting circuit 9 more than that at a weak electric field. As a result, an RF.AGC voltage at the strong electric field fed from the delay circuit 5 to a tuner circuit 1 is decreased further and the gain of the high frequency amplifier section of the tuner circuit 1 is decreased. Since the gain of an intermediate frequency amplifier circuit 2 is increased as it is, the overall gain is unchanged. Thus, the nonlinear distortion at the strong electric field is reduced while a sufficient S/N is ensured at the weak electric field.
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