基于零中频构架的OFDM射频调制系统设计

An OFDM RF modulation system design based on a zero intermediate frequency architecture

针对正交频分复用(OFDM)信号功率谱旁瓣干扰大以及数模转换(DAC)引起的镜频干扰,设计了一种基于AD9364射频收发芯片有效抑制带外干扰的OFDM射频调制系统。首先设计数字插值滤波器对信号进行内插处理,从而分离镜频;再通过高阶模拟低通滤波器滤除镜频,同时抑制OFDM信号旁瓣,加速旁瓣衰减。最后测试结果表明了所设计的OFDM射频调制系统能够有效抑制镜频及带外干扰,获得清晰准确的射频传输信号频谱。且节省了额外的FPGA资源,设计方案简单实用。

Orthogonal frequency division multiplexing(OFDM)signal has large sidelobe on its power spectrum,and digital to analog converter(DAC)brings the image frequencies interference. Aiming to this issue,an OFDM RF modulation system with out-of-band emission reduction is designed based on AD9364 RF transceiver chip. Digital interpolation filter is designed for separating the image frequencies.Then,the image frequencies can be eliminated by high order analog low pass filter,and the OFDM sidelobes can also be controlled at the meantime. The final test result shows that the OFDM RF modulation system designed can effectively restrain the image frequencies and out-of-band interference,and obtain a clear accurate RF transmission signal spectrum.This design saves the extra FPGA resources and the design is simple and practical.