another means is provided for generating a feedback signal to the predistortion generating mechanism so that the feedback signal is based on the output of the pa when the predistortion circuit is locked and is based upon the input signal to the pa when the predistortion generating circuit is unlocked undesired emissions from the power amplifier are inhibited when the predistortion mechanism is unlocked application_number US 34947989 A description fig1 illustrates a prior art implementation of a transmitter which utilizes a linear pa and circuitry for providing a predistorted signal to the pa this embodiment illustrates a signal sideband rf transmitter which includes a transmitter exciter 10 and a polar loop circuit 12 which provides a predistorted signal 14 to pa 16 the output 18 of the pa is coupled to antenna 22 by means of an rf coupler 20 which also samples the pa output signal the sample signal is attenuated by attenuator 24 before being coupled as the feedback input signal 26 to circuit 12 in circuit 12 an rf splitter 28 splits the input signal from exciter 10 and provides inputs to mixer 30 pll 32 and envelope detector 34 the output 36 of pll 32 provides the other input to mixer 30 the output of the mixer consists of a frequency translated signal which is filtered by bandpass filter 38 the amplitude of the signal is controlled by variable attenuator 40 the output of attenuator 40 consists of the predistorted.