| Summary: | 碩士 === 國立臺灣海洋大學 === 電機工程學系 === 94 === In wireless communications systems, the concept of software radio is to reduce the cost of the hardware modifications by implementing most of the receiver functions with software. The digital quadrature demodulation technique is one way to implement the concept of the software radio. This method first samples the modulated signal using a sampling frequency which satisfies certain conditions, then acquire the demodulated signal from the sampled signal via some very simple rules. If a bandpass sampling frequency is adopted, we can substantially lower the sampling frequency. This in turn reduces the cost and the complexity of the receiver. In this thesis, we try to solve the problems of carrier frequency offset and symbol timing synchronization
in multiband digital quadrature demodulators. We propose a method to achieve the symbol-timing and carrier recovery by using half band filters, the band-edge filters , and polyphase filter banks. The goodness of the proposed method is demonstrated by computer simulation.
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