差值量化椭圆球面波脉冲产生系统设计

Design of PSWF Pulse Generator Based on Difference Quantitation

为提高量化精度,降低量化存储空间需求,分析了直接数字波形合成椭圆球面波函数(prolate spheroidalwave function,PSWF)脉冲产生系统的幅度量化误差,指出了影响量化精度的主要因素,进而提出一种差值量化PSWF脉冲产生系统的改进设计方案.该方案对采样幅度差值进行量化存储,代替采样幅度直接量化存储的方法,并对数模转换模块进行改进.理论分析和仿真实验表明:当过采样率大于π时,采用差值量化代替直接量化有助于改善量化噪声功率谱.过采样率每提高1倍,可使量化噪声功率谱改善6 dB,优于直接量化方式3 dB.同样的量化位数情况下可获得更高的量化精度,在相同量化精度要求下可有效降低存储空间需求.差值量化PSWF脉冲产生系统更适合于高采样率、高精度的PSWF信号产生.

To get higher accuracy of prolate spheroidal wave function （PSWF） pulse generator and reduce quantization bits, quantization error in the traditional PSWF generator based on direct digital waveform syn-thesis （DDWS） is analyzed. The main factors that affect quantization accuracy are listed. A design method for PSWF pulse generator based on difference quantitation is proposed. The method uses difference quantitation rather than direct quantization and modifies the DAC module. Theoretical analysis and simulation show that, as the over sampling rate （OSR） is greater than ~, difference quantitation can improve the noise spectrum. When OSR is doubled, the noise spectrum is improved by 6 dB, as compared to 3 dB of direct quantitation. The difference quantitation method has higher quantitation accuracy with the same or even less number of quantitation bits. Therefore, PSWF pulse generator based on the difference quantitation is more suitable for high-precision PSWF signal generation with high sampling rate.