PURPOSE: To reduce the disturbance due to a double higher harmonic and the degradation of NF and attain a sufficient separation, by using BPFs in the input stage and providing a high frequency amplifying circuit in the preceding stage of a switch circuit and turning on and off the power source of said amplifying circuit in accordance with the switch circuit.
CONSTITUTION: The signal from an antenna 1 is divided into N by BPFs 2-1'∼ 2-N'. The N-divided signals are amplified by amplifiers 13-1∼13-N and are inputted to a high frequency changeover switch 3'. This changeover switch 3' selects the output signal of one of amplifiers 13-1∼13-N in accordance with output signals 4-1∼4-N of an external switching signal circuit 4' by a switch diode. A power supply circuit of amplifiers 13-1∼13-N is so constituted that only signals of a band which the high frequency changeover switch 3' selects in accordance with output signals 4-1∼4-N of the external switching signal circuit 4' are inputted. The output of an AGC circuit 5 passes through a known circuit shown in Fig. and an intermediate frequency output is obtained in a terminal J.
USUI AKIRA
NAGAI HIROYUKI
| JPS49131009A | 1974-12-16 | |||
| JPS5590142A | 1980-07-08 |