| 摘要 |
PROBLEM TO BE SOLVED: To provide a receiver which uses a digital filter and also can be fast transmitted at low cost. SOLUTION: This amplifier circuit includes a level detection circuit 7 which detects the levels of received signals not yet digitized, a level decision circuit 8 which decides the signal levels detected by the circuit 7, the analog amplifiers 2, 4 and 6 to which the received signals not yet digitized are inputted and a series circuit of analog variable attenuators 3 and 5. The circuit 8 outputs a control signal to set the large attenuation to the attenuators 3 and 5 when the decided signal levels are larger than the prescribed value. The output signals of a variable attenuator 6 are digitized by a semi-synchronization detection part 102 and supplied to digital filters 17 and 18. The output signals of the filters 17 and 18 are amplified by limiting amplifiers 19 and 20 constituted of digital circuits and then outputted to a demodulation circuit 21. |
