| 摘要 |
PURPOSE:To simplify the structure of a signal extracting part and at the same time to obtain a general-purpose IC by providing a frequency counting means for transmission power and changing the reactance in accordance with the counted frequency. CONSTITUTION:A matching circuit 9 serves as a reactance circuit network containing three pairs of variable reactance circuits. Each of the reactance circuits consists of capacitors 3 and 4 and a coil 5. The transmission power is sent to an antenna 7 from a transmitter 1 via an antenna coupler 8 through a channel of a comparatively high transmission/reception frequency band. Thus the output terminal D1 of a latch circuit 19 is set at H level in response to the count value of a counter 17 of a frequency counter 10. Then a switch S1 is actuated. Therefore a reference potential point (earth) is connected to the terminal L1 of the circuit 9. Thus the inductance of a coil 5 is reduced and the antenna 7 of the transmitter 1 is controlled. |
