一种DDS任意波形发生器的ROM优化方法

A ROM optimization method of DDS-based arbitrary waveform generator

提出了一种改进的基于直接频率合成技术(DDS)的任意波形发生器在现场可编程门阵列(FPGA)上的实现方法。首先将三角波、正弦波、方波和升/降锯齿波的波形数据写入片外存储器,当调用时再将相应的数据移入FPGA的片上RAM,取代分区块的将所有类型波形数据同时存储在片上RAM中的传统方法;再利用正弦波和三角波的波形在4个象限的对称性以及锯齿波的线性特性,通过硬件反相器对波形数据和寻址地址值进行处理,实现了以1/4的数据量还原出精度不变的模拟信号,从而将整体的存储量减小为原始设计方案的5%。经验证,这种改进方法正确可行,能够大大降低开发成本。

This paper presents an improved method of arbitrary waveform generator based on direct digital frequency synthesis （DDS） technology achieved on field programmable gate array（FPGA）. First, it writes the waveform data of triangle wave, sine wave,square wave, and ascending or descending sawtooth wave data to the off-chip memory, and moves the corresponding data into FPGA on-chip RAM when it is invoked, which replaces the traditional method that stores all types of waveform data in on-chip RAM sub-blocks. Then, it takes use of the symmetry of sine and triangle waveform in the four quadrants, and the linearity of the sawtooth waveform, process the waveform data and the address value by hardware inverter. It can restore the same-precision analog signal with a quarter of the amount of data. The overall storage capacity is reduced to 5% of the original design. After validation, this improved method is feasible, and it can greatly reduce the development costs.