To provide a small-sized transmitter-receiver.
This transmitter-receiver has a microcomputer 16, a transmitter- receiver antenna 24, a filter 26, in which a signal in a specified frequency band containing frequency f1 and the frequency f2 of a signal from a fixed transmitter-receiver 12 is passed, an antenna changeover switch 28, an oscillation circuit 30 oscillating the signal of frequency f1 modulated by a signal from the microcomputer 16, an RF amplifier 32 amplifying a signal from the oscillation circuit 30, an RF amplifier 34 amplifying a signal from the antenna changeover switch 28, a mixer 36 mixing a signal from the RF amplifier 34 and a signal from the oscillation circuit 30 and coverting the mixed signals into an intermediate-frequency signal and a detector 38 detecting an original signal from the intermediate-frequency signal of f0 (f2-f1). The generation of a transmitter-receiver signal and local oscillation in demodulation are conducted by one oscillation circuit.
SHIBAGAKI YUJI
ITO MICHIMASA
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