Analysis and design of an adaptive polynomial predistorter with the loop delay estimator

Most adaptive linearization circuits for the nonlinear amplifier have a feedback loop that returns the output signal of the amplifier to the linearizer. The loop delay of the linearizer must be controlled precisely so that the convergence of the linearizer should be assured. In this Letter a delay control circuit is presented. It is a delay lock loop (DLL) with a modified early–late gate and can be easily applied to a DSP implementation. The proposed DLL circuit is applied to an adaptive linearizer with the use of a polynomial predistorter, and the simulation for a 16‐QAM signal is performed. The simulation results show that the proposed DLL eliminates the delay between the reference input signal and the delayed feedback signal of the linearizing circuit perfectly, so that the predistorter polynomial coefficients converge into the optimum value and a high degree of linearization is achieved. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 117–121, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10391