1.25GSPS任意波形发生器滤波电路的设计

Filter design for 1.25GSPS arbitrary waveform generator

直接数字式频率合成技术(Direct Digital Synthesis)广泛应用于任意波形发生器中,其全数字的结构导致输出信号中含有大量杂谱曲线;本文分析了1.25GSPS任意波形发生器中DDS信号发生模块的频谱情况,得出对所有频率的正弦信号可以用一路椭圆低通滤波器进行滤波处理,任意波则使用群延迟特性良好的线性相位滤波器滤波的结论;由此制定了对应的滤波电路方案。此外,本文还简单描述了椭圆滤波器的阶数的确定方法;对综合出的电路进行了仿真;最后,使用矢网分析仪对实际电路进行了S参数测试,验证了设计的正确性。

DDS （Direct Digital Synthesis） is a new kind of frequency synthesizing technology that is widely u applied in arbitrary waveform generator. Due to its all-digital architecture, spurs in the output is unavoidable. The paper analyzes the output spectrum of DDS and reaches a conclusion that all spur can be filtered off by an elliptic low-pass filter. An overall filter design program is put forward. Besides, the paper describes how to figure the order of the elliptic low-pass filter simply. The filter is designed and simulated. In the end, it is proved that the design is feasible by the S-parameter test results.