| 摘要 |
An output level control circuit for radio-frequency transmitter which intermittently transmits radio-frequency carrier waves such as seen in the TDMA radio communication system and the digital cellular mobile telephone system. The variable gain amplifier unit of this transmitter amplifies the transmitting signal to a predetermined output power level in response to a control signal, the output power level is detected by a detecting diode which receives the application of a temperature-compensated bias voltage, and the sum of the detected output and the bias voltage becomes the detection output to the control loop. The bias voltage of the detecting diode is stored by bias voltage detection means during the off-period of the transmitting signal, an input reference voltage that is supplied in synchronism with the turning-on of the transmitting signal and the stored bias voltage are added by reference signal addition means, and the added output is served as the reference voltage that corresponds to the predetermined output power level. Power control means generates the control signal in response to the added output and the detection output, and the control signal controls the output power level of the variable gain amplifier unit.
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