PURPOSE: To obtain a transceiver circuit which can efficiently supply high-frequency pulses into a probe up to a high frequency region.

CONSTITUTION: High-frequency pulses from a transmitting circuit 1 are sent into a probe 2. The resonance signal from the probe 2 is sent into a receiving circuit 4 through a transmission line transformer 3. A switching circuit 5 is inserted into the primary side of the transmission line transformer 3. In order to turn ON and OFF the switching circuit 5, a peak detecting circuit 6 and a driving circuit 8 for driving the switching circuit 5 based on a blanking signal are provided. A negative voltage is outputted from the peak detecting circuit 6 during the period wherein the high-frequency pulses are generated. Thus, the switching circuit 5 is not biased and the impedance of the transmission line transformer becomes high. as a result the high-frequency pulses flows into the probe. During the period wherein the high-frequency pulses are not generated (receiving period), the driving circuit 8 is ON, and the switching circuit becomes also ON. The impedance of the transmission line transformer becomes low. Therefore, the resonance signal from the probe is sent into the receiving circuit 4.