| 摘要 |
PURPOSE:To attain the transmission and reception over the desired entire communication frequency band by the transmitter-receiver of the same constitution by constituting a reception frequency conversion section so as to cancel an image frequency and providing a changeover means for the relation of upper/ lower state of a local signal frequency and a desired reception frequency. CONSTITUTION:A local signal outputted from a local oscillator 1 is inputted to mixers 3, 4 via a 0-90 deg. distributer 2. The signal at a reception input 9 is inputted to mixers 3, 4 in in-phase. Since the phase difference between the signal of the mixer 4 and the image signal and the desired reception signal of the mixer 3 is +90 deg. or -90 deg., the intermediate frequency signal extracted from the mixers 3, 4 is cancelled at a 0-90 deg. synthesizer 5 while bringing the phase of the image signal to be inverted to extract only the desired reception signal. Moreover, when the desired reception signal frequency is lower than the local signal frequency and the circuit is operated normally, a changeover switch 6 is switched to bring the desired reception frequency more than the local signal frequency to attain the operation.
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