Study Of Some Key Problems In Mixed-Signal Processing For CDMA Communication Systems

Owing to its advantages in spectrum efficiency, multiple-access capacity, overcome wireless-channel fading, soft switching, improved traffic capacity, etc, Code-Division- Multiple-Access (CDMA) is becoming the primary multiple-access technique in digital mobile communication systems, wireless local area network, personal communication systems, and so on. With the increasingly function of digital signal processing algorithms and the development of the integrated circuit technology, many signal processing function are carried out in digital domain. Since the restrict of the word length of A/D converters and the filter orders, the digital implementation is large in size which make it difficult to reduce the power consumptions and can not satisfy the demand of the next-generation wireless applications. On the basis of the theory of nonuniform bandpass sampling, the theory of quadrature detection, the theory of matched filters, the principle of CMOS operational amplifier and the principle of neuron MOS device, a mixed analog-digital algorithm of signal processing for the mobile communication terminals of DS-CDMA system is proposed. Both the arithmetic principle and the mixed analog-digital circuit structure have been carefully studied, and the arithmetic performance is finally discussed. In brief, the following major creative results have been obtained:1. The spectrum aliasing in high-order nonuniform bandpass sampling is analyzed in detail. And on the basis of the analysis, the conditions of the Fourier images of interpolants are given in the recovery of bandpass signal without distortion. Based on the band-limited signal model of generalized sampling theorem, the reconstruction of a real bandpass signal from nonuniform samples is discussed. The computing of the Fourier images of reconstructing functions is become the calculation of the solution of a set of linear equations which can be solved by Cramer's rule, and the Fourier images of reconstructing functions is the solution of the set of linear equations. Finally, the simulation example is presented to illustrate the reconstruction of bandpass signal.2. A novel mixed analog-digital algorithm of despreading for QPSK modulated WCDMA signals is presented. In this algorithm, the spreading bandpass signal is firstly sampled and held with the second order sampling...