利用DCT有效实现正交复用QAM系统

An Efficient Realization of Orthogonally Multiplexed QAM System Using Discrete Cosine Transform

正交复用 QAM(O-QAM)系统是一个相邻载频间隔为波特率的多路系统,可以用数字信号处理技术实现.这种系统在复用路数无限增加时可以达到奈奎斯特速率,并且对传输媒介引超的延迟和幅度失真不灵敏.本文提出用离散余弦变换(DCT)处理器级联一个权重网络实现 O-QAM 系统的新方案.该方案由于充分利用了 FIR 滤波器系数的对称性,使权重网络计算量明显下降.DCT 通过快速卷积算法获得,总计算量明显下降.

An orthogonally multiplexed QAM(O-QAM)system is a multichannel system with a baud rate spacing between the adja- cent carrier frequences and can be implemented by digital signal processing(DSP)technique.This system allows the transmission speed very close to the Nyquist rate with little sensitivity to delay and amplitude distortion caused by the transmission medium when a large number of channels are used.In this paper,a new scheme to realize O-QAM system by means of cascading a discre- te cosine transformer(DCT)and a weighting network is presen- ted.By using the symmetry of coefficients of FIR filter in the weighting,network and fast convolution algorithm for evaluating the DCT,the computation complexity is reduced to 56.9 percent of that by Hirosaki's scheme.