JPS5642437A - Radio receiver - Google Patents

Abstract

PURPOSE:To make it possible to avoid a dead point due to multipath by setting a local oscillation frequency to (f1+f2)/2 (f1 and f2 are carrier frequencies) and by providing an intermediate frequency amplifier that has its intermediate frequency set to (f1-f2)/2. CONSTITUTION:In receiver B, received signals from receiving antennas 21 and 22 are inputted to high frequency amplifying circuit 4, but circuit 4 includes filters F1 and F2 that have their peaks of passing bands at carrier frequencies f1 and f2 and the received signals of frequencies f1 and f2 are amplified and applied to mixing circuit 6 at the following stage. Next, since local oscillating circuit 5 is so set that it will oscillate at frequency (f1+f2)/2, intermediate frequencies obtained by circuit 6, when the received signals of f1 and f2 are inputted, are considered to be (f1-f2)/2 and -[(f1-f2)/2] by calculation and in any case, an intermediate frequency output of (f1-f2)/2 is supposed to be obtained by circuit 6. Thus, the reception output that corresponds to frequency f1 or f2 is to be obtained, so that the communication can be prevented from being disabled due to a dead point.