OFDM系统中频数字接收机的工程实现

Project Realization of Digital Intermediate Frequency Receiver of OFDM System

对带通采样理论进行了简单介绍,并对带通欠采样数字正交解调进行了详细的数学推理,并介绍了一种数字中频接收机的工程实现办法。该数字接收机具有较大的动态范围,较高的I,Q输出精度,采用带通欠采样进行中频采样,数字滤波法进行数字正交相干解调。介绍了传统模拟中频接收机的不足和数字中频接收机的优点,根据本课题的技术指标要求进行了中频数字接收机的设计,包括中频放大电路和数字控制VGA、数字中频A/D采样和数字相干解调。结果表明,两路信号幅度的误差<0.4%,相位的正交误差<0.4%,满足了设计指标要求,技术指标明显优于传统的模拟接收机。

The bandpass undersampling theory and the detailed mathematical reasoning of bandpass undersampling digital quadrature coherent demodulation were introduced,and a digital IF receiver of OFDM system was presented.The digital receiver is with larger dynamic range,higher I,Q output precision,using bandpass undersampling method for IF sampling,digital filtering method for digital quadrature coherent demodulation.The shortage of traditional analog receiver and the advantages of digital receiver were described.In accordance with the technical specification of the subject requirements,a digital IF receiver was designed,including IF amplifying circuit,digitally controlled VGA,digital IF A/D sampling and digital coherent demodulation.The results show that the error of amplitude is〈 0.4% and the error of phase quadrature is〈 0.4%,it meets technical requirements and is better than traditional analog receiver.