Abstract: A radio transmitter includes a power amplifier (12); a linearizer (10) for maintaining linearity in the power amplifier; and a feedback path (13) for feeding a signal from an output of the power amplifier to the linearizer. The amplifier, linearizer and feedback path cooperate to form a feedback loop having adjustable loop linearization parameters (for example phase and gain). Further, a look-up table (19) is used to store predetermined loop linearization parameters and cooperates with a microprocessor having an operating condition input.

Abstract: A radio transmitter circuit is provided comprising: a power amplifier coupled to an antenna for transmission of radio signals; linearizer means, such as a Cartesian feedback linearizer or a predistortion equalizer, for compensating for non-linearity in the power amplifier; means for inputting a training sequence to the linearizer means and outputting a training signal from the power amplifier resulting from the training sequence; and a feedback circuit for feeding the training signal output from the power amplifier back to the linearizer means to adjust the linearizer means and/or feedback circuit. Means are provided for inhibiting transmission of radio signals through the antenna while the training signal is being output from the power amplifier.

Abstract: A power amplifier is described, such as an amplifier employing closed loop feedback (e.g. Cartesian feedback) as well as a radio transmitter incorporating such an amplifier. The amplifier circuit has an amplifier control loop and a loop closing element (18, 107) for selectively opening and closing the control loop in response to a loop closing signal (40). One or more gain elements (30, 31, 32, 33, 101, 102, 110, 111) external to the control loop is adjusted responsive to the loop closing signal so as to maintain approximately constant gain between the input and the output of the amplifier during opening and closing of the loop, Because the gain adjustment is carried out external to the loop, any negative impact on the phase shift or phase stability is reduced or eliminated, and the circuit can be designed with reduced phase margin and greater simplicity.