| 摘要 |
PROBLEM TO BE SOLVED: To provide a multifrequency transmitter-receiver circuit capable of achieving tuning by efficiently adjusting resonance capacitance and further reducing spurious oscillation.SOLUTION: A multifrequency transmitter-receiver circuit comprises: a coil 2; one main capacitor 51 having main capacities connected to the coil 2 respectively in series and connected to each other in parallel; a resonator composed to a plurality of capacitors 5 consisting of one or a plurality of correction capacitors 52 having a correction capacity less than the main capacity; a plurality of switch elements 7 turned ON and OFF on receiving a capacity control signal and having a diode connected in series with each capacitor 5 to allow a current in a reverse direction; and an inverter 20 connected to the coil 2. A switch element 7 for controlling conduction of the main capacitor 51 has a series circuit of a resistance 511 and a capacitor 512 for spurious suppressing in parallel, and a resonance frequency of a resonator 1 is adjusted by selecting the main capacitor 51 for activating the switch element 7 and an added correction capacitor 52.SELECTED DRAWING: Figure 6 |
