基于双口RAM的自适应数字式预失真器

An Adaptable Digital Predistorter Implemented by Dual RAM

数字音频广播(DAB)系统采用的是编码正交频分复用(COFDM)传输技术,具有频谱利用率高及适于移动接收等优点。但其调制信号包络具有很高的峰均功率比(PAPR),当发射机中高频功率放大器(HPA)工作于非线性区时,会产生频谱扩散及带外干扰。为了线性化HPA,文中利用双口RAM的特点,设计了一种自适应数字式预失真器,并给出了具有良好收敛能力的可变迭代因子误差校正算法。电路测试结果表明,该预失真器可有效改善放大器的非线性区,对谐波失真及二阶互调失真等有较好地抑制作用。

The DAB system adopts COFDM transmission technology which possesses the advantages of high use ratio of frequency spectrum and suitability for mobile receiving. While the enrelopc af the modulation signal has high PAPR. When the HPA in the transmitter works in nonlinear area, the frequency spectrum diffuse and out-off-band interference will be produced. TO make linear for the HPA, the paper designs an adaptable digital predistorter using the characteristic of the dual RAM, and gives a variable itera- tion.factor algorithm for error correction which shows good iteration ability. The circuit test result show that the predistorter can effectively improve the nonlinear area of the amplifier, and performs good limitation to the harmonic distortion and second order intermodulation distortion.