PURPOSE: To realize both the low cast of the device and the low power consumption by sharing one unit of the amplifying circuit for both the amplificatin of the transmision signal and the oscillation of the local oscillation signal.

CONSTITUTION: The intermediate frequency signal sent from input 4 is transmitted from terminal 13 through BPF8 whose central frequency is the transmission signal frequency as well as circulator 18 after passing through frequency mixer 3 and transmission power amplifier 12 each. On the other hand, the local oscillation signal is obtained by installing the positive feedback loop which gives the reflection to the signal from terminal 5 of mixer 3 and at BPF8 via amplifier 12 and circulator 18 and then returns it to terminal 5 through attenuator 15, BPF16 (with the central frequency of the local oscillation signal frequency) and phase controller 17 each, and by giving the oscillation to amplifier 12 after setting 15 the feed back amount to the optimum level. In this case, amplifier 12 is used for both the local oscillation signal and the transmission signal, and thus the active circuit exclusive for the local oscillator can be omitted to realize the economization.