Baseband Modem Design Of Variable Rate

Following the guidance of software radio and digital demodulation theory, based on the software platform of systemvue which is developed by Agilent,theπ/4-QPSK andπ/4-DQPSK baseband modem is designed in this thesis. We mainly aimed at the hardware design library of Systemvue. With the help of the HDL Generation function built in the software, designers can switch over from the visual model to the standard hardware language conveniently.Multi-Rate signal processing is a basic theory in software radio. It changes the rate of digital signals by decimation and interpolation. Based on the multi-rate theory, this thesis constructed a standardized, modularized hardware and software platform. And only need one set of hardware devices, we can perform the whole modem system of variable rate. With this method, we can not only reduce the occupancy factor of the hardware resource, but also make the design have great flexibility and general applicability. Besides, the system is available for extension.In addition. symbol synchronization or timing recovery is one of the most critical parts in the receiver, which directly influences the performance of the whole system. The software systemvue doesn't support irregular clock. so in order to solve the problem. a new approach for performing the interpolations in GAD algorithm is proposed in this paper, by employing a polyphase filterbank. This method takes advantage of the polyphase version to achieve the interpolation (upsample) of the receive signals, without changing the sample rate of the signals.In order to measure the performance of the system, we should assert some noises to the useful signal. This paper gived a method to generate the white Gaussian Noise based on the center limit theorem. Simulation results using Matlab agree with the theoretical analysis. At last, the bit error rate in different SNRs is tested with the Error-code Analyzer. The results indicated that the system has a good anti-noise performance.