Transmitter having an improved power added efficiency and radio using same

摘要

A radio (300) has a transmitter (302) comprising a power amplifier (308), a voltage conditioner (318), and a controller (313). The power amplifier operates at one of a plurality of output power levels. When the output power level is reduced from a maximum setting to a lower setting, the controller adjusts a control signal level provided to the voltage conditioner. The change in control signal level selects a lower output voltage from the voltage conditioner, which is supplied to the power amplifier. By selectively adjusting the voltage level supplied to the power amplifier, the power added efficiency is maintained at an optimum level. The voltage conditioner may be a switched mode converter of buck, boost or buck/boost type.