| 摘要 |
PURPOSE:To prevent an unnecessary signal component from being leaked to the 2nd frequency conversion section, by making band pass characteristics from the 1st frequency conversion to the 2nd frequency conversion section steep. CONSTITUTION:In a series resonance trap circuit 13, the resonance frequency is set to a prescribed frequency f1 higher than the frequency of the 1st IF signal outputted from the 1st mixer 5, and the trap characteristics as shown in a figure are applied to an output signal of an IF amplifier 7. Thus, in inserting a series resonance trap circuit 13 between the IF amplifier 7 and the 2nd IF filter 10, the overall characteristics from the 1st frequency conversion section 3 to the 2nd frequency conversion section 8 are attenuated further at the skirt of the band pass characteristics. |
