Research On Power Amplifier Based On Least-Mean-Square Algorithms

In radio access layer, the quality of net will be higher and higher by the coming era of the 3rd generation communication system. The traditional GSM repeaters are not available for WCDMA system. This article advised that use the method of digital signal process to amplifier the base band signal and restrain the adjacent channel power ratio (ACPR) for higher frequency and wider band wide.This article analyzes the theory of repeaters at beginning. And propose the architecture of repeater, which used in WCDMA system. It references the traditional repeater, and consults a process method for base band signal. Then do a research of pre-distortion algorithm and practice in the amplifier module. This is the key and innovative point of the whole article, and first mentioned in this area. LMS (least-mean-square) algorithm was run application here in this system, which use for calculate the difference between input signal and feedback signal. And then the system will get a value to correct the input signal. So the distortion was in a regular way. Mean time, this system is a close-loop system, which has the function of self-adaptation.During this project, the LMS algorithm was be improved many times by thousand times of practice. Pre-distortion micro-chip ISL5239 and digital signal process micro-chip TMS320C3X were used in this system. An emulator was run to simulate whole system before it was build up to make sure the result would be closer to the real system. And each module had been test many times to ensure each of them can provide correct parameters.The designed equipment presents a distinct score. Its output power is 14% higher compare with traditional one. And the value of ACPR decreases 13dB. Simultaneously, the 3^rd intermediation minimizes 9dB.In all, this article induces digital signal process method into RF signal area. Combine LMS algorithm and make use of the theory of self-adaptation to improve the traditional power amplifier. It will bring meaningful sense to the area of power amplifier domestically.