Adaptive digital linearization of a DRP based edge transmitter for cellular handsets

2007 50th Midwest Symposium on Circuits and Systems Pub Date : 2007-08-01 DOI:10.1109/MWSCAS.2007.4488676

K. Waheed, S. Ba

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引用次数: 8

Abstract

The digital RF processor (DRP) based EDGE small- signal polar transmitter utilizes a highly non-linear digitally controlled pre-power amplifier (DPA) for on-chip combination of the amplitude and phase modulation paths. This complex signal drives an off-chip power amplifier (PA), optimized for power added efficiency (PAE), causing further degradation in the linearity of transmission. We propose an effective adaptive predistortion scheme that takes advantage of the time division duplex (TDD) nature of the EDGE modulation and uses the on-chip receiver as a feedback path during transmission. The proposed linearization technique features automatic calibration of nominal AM-AM and AM-PM look-up tables (LUT). The temporal variations primarily caused by temperature, aging, impedance and voltage changes are compensated by an incremental predistortion function that is periodically adapted using a low complexity iterative algorithm. The proposed predistortion technique improves the EDGE TX error vector magnitude (EVM) contribution from -20 dB (or 10%) in absence of predistortion to -67 dB (0.04%) while the adjacent channel power ratio (ACPR) at 400 kHz offset improves from -46 dBc to -69 dBc.

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基于DRP的手机边缘发射机的自适应数字线性化

基于数字射频处理器(DRP)的EDGE小信号极性发射机利用高度非线性的数字控制前置功率放大器(DPA)进行片上幅度和相位调制路径的组合。该复杂信号驱动片外功率放大器(PA)，优化功率附加效率(PAE)，导致传输线性度进一步下降。我们提出了一种有效的自适应预失真方案，该方案利用EDGE调制的时分双工(TDD)特性，并在传输过程中使用片上接收器作为反馈路径。提出的线性化技术具有自动校准标称AM-AM和AM-PM查找表(LUT)的特点。主要由温度、老化、阻抗和电压变化引起的时间变化由增量预失真函数补偿，该函数使用低复杂度迭代算法进行周期性调整。提出的预失真技术将EDGE TX误差矢量幅度(EVM)的贡献从无预失真的-20 dB(或10%)提高到-67 dB(0.04%)，而400 kHz偏移的相邻通道功率比(ACPR)从-46 dBc提高到-69 dBc。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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2007 50th Midwest Symposium on Circuits and Systems

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