| 摘要 |
PURPOSE:To improve greatly the power efficiency and at the same time to simplify the constitution of an amplitude modulating circuit, by superposing a modulating signal on the reference voltage of a switching regulator circuit of a power supply for a carrier power amplifier and then modulating the amplitude of the carrier wave. CONSTITUTION:A carrier power amplifier is provided with a transistor TR13, a transformer Tf11 and a capacitor C14. For a modulating signal amplifier IC12, a modulating signal is superposed on the reference voltage generated from a Zener diode D12 and a resistor R12 which constitute a switching regulator. This superposed signal and voltage is used to a positive input of a comparison amplifier IC11. The voltage E0 which is supplied to the carrier power amplifier as a negative input of the amplifier IC11 is equal to (ERef+e) (R16+R17)/R17, and the amplitude is modulated for the output of the carrier power amplifier. In this case, ERef means the reference voltage produced at the diode D12 and (e) is the voltage of the modulating signal. In such a constitution, the efficiency of the electric power supplied to a power amplifying circuit is greatly increased. In addition, a power transistor is eliminated to simplify the constitution of an amplitude modulating circuit. |
