基于改进CORDIC算法的数字预失真实现

针对传统CRODIC算法存在的角度扩展、迭代复杂度等问题,在旋转模式下提出一种改进型CORDIC算法。对于旋转角度范围的扩展,采取将向量限制在第一和第四象限,旋转最后再根据输入向量符号判断旋转角度值;对于迭代复杂度,采用跳跃旋转方式来减少迭代次数。最后在Quartus软件上实现了该改进算法,并且将改进后的CORDIC算法应用于数字预失真技术,在FPGA上设计实现。仿真与实验结果表明:与传统的CORDIC算法相比,改进算法减少了硬件的开销,运算速度和精度都有很大改进,能够快速提取预失真参数,显著提高功率放大器的线性度。

Implementation of Digital Pre-distortion Based on Improved CORDIC Algorithm

According to the problem of the traditional CORDIC algorithm, such as angle extension and iteration complexity, a modified CORDIC algorithm is proposed in rotation mode. For the range extension of rotation angle,the vector is limited to first or fourth quadrant and the value of rotation angle is determined according to sign flag which is the flag of input signal at the end of rotation. For the complexity of extra iteration, the basic idea is to use skipping rotation to reduce the number of iterations. Finally, the improved algorithm is implemented with the Quartus Ⅱ software, and the improved CORDIC algorithm is applied to digital pre-distortion technology with FPGA. The simulation results show that compared with traditional CORDIC algorithm, the proposed algorithm can reduce the cost of hardware,improve computing speed and precision,and also extract the pre-distortion parameters rapidly, and simulta- neously ensure the linearity requirement of power amplifier.