Research On Base-band Predistortion Algorithm

High Power Amplifier (HPA) is an important component in the transmitter. In engineering, good linearization of HPA is required, especially in OFDM and WCDMA system. However, in reality, the nonlinearity and memory effect of HPA cause the gain of transmitter not a constant. There are many methods for linearization. Among these, the most effective method is a class named as pre-distortion. This method is to place a nonlinear device to compensate the memory effect of HPA. In this method, base-band pre-distortion is believed as an excellent method.Classical base-band pre-distortion algorithm is designed base on adaptive filter. The feature is that it can linearize the polynomial model of HPA effectively. However, it causes heavy computing complexity at the same time. Though observing the classical base-band mathematic model of HPA, we put forward a novel base-band pre-distortion in this article. This method discard the adaptive filter mode adopt in classical method. The pre-distortion algorithm is realized through reverse solving the base-band model of HPA, for this reason, it can get better tradeoff between accuracy and rapidity. Considering the precision loss of division and root square operation caused by quantization effects, this article transforms the expression of pre-distorter by excluding above operations. In the final expression, it includes only multiple and addition operation, which is not sensitive with limited-bits float operation. This transform improves the perform ance of pre-distortion greatly.In this article, Designs are given towards the non-memory and memory model of HPA separately. Among these, reversal filter is used for compensating the memory effect in the design for memory model of HPA. At the same time, this article also discusses the design of hardware architecture. A processing structure with pipeline-like character is proposed based on the improvement expression of pre-distortion. This hardware structure improves the capacity of signal processing. Moreover, it is easy designed by module or even, parallel processing.