| 摘要 |
PURPOSE:To correctly detect reflected power regardness of the length of an antenna feed line and the mismatching position of impedance by holding the detected value of a reflected power detecting circuit into plural sample holding circuits and selecting the max. value thereof. CONSTITUTION:The reflected power detecting circuit 3 detects the reflected power at the transmission line between the output terminal of a power amplifier circuit 2 which amplifies the high-frequency power and an antenna input terminal 5. A phase shift circuit 4 is inserted between the circuit 3 and the terminal 5 and the phase shift quantity of the circuit 4 is controlled at a prescribed period by a shift quantity control signal 107a from a control signal generating circuit 7. The sample holding circuits 8, 9 sample and hold the detected value 3 at the points of the sampling time different from each other in synchronization with the signal 107a. A selection circuit 10 is inputted with the holding voltages 108, 109 of the circuits 8, 9, select the larger holding voltage and output the same as a reflected power signal 110 to an output terminal 12.
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