Power amplifier for radio transmitter and dual mode remote radio

摘要

A power amplifier for a radio transmitter is described. For operation at optimum efficiency, the amplifier has a bias level control input (52) for control of direct current power consumption by the amplifier (50). A sample-and-hold arrangement (80) sampling signals output from the amplifier over a first period of time. Computations are performed (13, 86) on the signals sampled; and the bias level input of the amplifier is adjusted at a time following the first period of time. The arrangement is particulary suitable for use in a radio system comprising a remote radio (10) and a base station (20) where the radio is arranged to operate in a first mode under the control of the base station (e.g. trunked mode) and a second, direct radio-to-radio, mode of operation.