RADIO TRANSMITTER/RECEIVER

摘要

The object of the present invention is to realize a radio transmitter/receiver in which a receiving local oscillation means composed of a PLL including a dividing circuit is free from an erroneous operation due to an invasion of a transmitting signal and a suppression of power consumed is achieved. A frequency mixing circuit 3 receives a local oscillation signal S3 from a receiving local oscillation means 5 and converts a receiving signal S1 into an intermediate frequency signal. A transmitting section 6 output a transmitting signal S4 during talking. A transmitting detection circuit 7 detects the transmitting signal S4 to output a transmitting detection signal S5. An amplifying circuit 51 of receiving local oscillation means 5 is supplied with a current from a current source circuit 52 and amplifies the local oscillation signal S3. The current source circuit 52 increases the supply current upon the receipt of the transmitting detection signal S5 and increases the gain of the amplifying circuit 51. A rejection filter 86 is constituted such that the rejection filter 86 exhibits a low impedance for the frequency of the transmitting signal. A switch 53 is rendered to be in the ON state upon the receipt of the transmitting detection signal S5 so that the rejection filter 86 function to attenuate the transmitting signal which interferes into the dividing circuit.