| 摘要 |
PROBLEM TO BE SOLVED: To always obtain the best reception quality by making it possible to optionally adjust the center frequency, band width, and noise convergence point of an IF filter only under the control of a CPU at the time of shipment or at a shipment destination and since they are adjusted according to the shipment destination and monitoring the center frequency of an IF filter even while a radio broadcast is received. SOLUTION: This amplifier 11 has band-pass notch filters composed of a low-pass notch filters LPN (LPN1 to LPN4) and high-pass notch filters HPN (HPN1 to HPN4), those band-pass notch filters are connected in plural stages, and only the final stage can be adjusted by a CPU 14. A noise convergence point trimmer circuit 22 which is adjusted by the CPU 14 is arranged in front of the band-pass notch filters of the stages. Further, an IFAGC circuit 25 monitors not only an IF output, but also the output of the initial-stage band-pass notch filter to control variable gain amplifiers VCA (VCA1 and VCA2). |
