Currently, the only available wideband (multiple MHz), accurate, amplifier linearization method is feedforward. Feedforward, though, requires automatic adaptation of key parameters for reliable distortion cancellation as operational and environmental conditions vary. In this thesis, previous analysis on adaptive feedforward linearization is extended to include an _alternative placement of the adaptive signal cancellation coefficient.In contrast to previous analysis, this placement results in a non-quadratic error surface. Consequently, two available criteria for the optimization of the signal cancellation coefficient result in different optimal values. This result can have practical implementation consequences under certain operating conditions. A new analysis is presented that shows that various inaccuracies & the implementation of baseband correlation, such as frequency and phase oeets, filter mismatches, and incomplete image suppression, do not affect the final converged coefficient values. With a novel and appropriate use of DSP, a feedforward linearizer has been implemented with adaptation driven by easily computed gradient signals. This overcomes the dficulties, such as DC -. offsets at the output of analog mixers and masking of weak signals by stronger ones, that slow and/or cause incorrect convergence of many previously reported implementations. The result is 40 dB reduction of intermodulation spectra over a bandwidth of 7 MHz. Coefficient convergence occurs within 50 msec of start-up, and following a 6 dB change in input power, reconvergence occurs \in 3 msec with no loss in distortion suppression.
ACKNOWLEDGEMENTSNothing is ever done alone; thus, I would like to thank certain people who helped me along the way with this project. Thanks to my Senior Supervisors, Jim Cavers and Paul Goud, who, I feel, were responsible for advancing my knowledge and confidence in the area of wireless communications to a new and hopehlly much higher level than before.Deserving of thanks as well, is my wife, Irma, for her constant support the whole way through the project, fiom start to finish.
