Research On Algorithm And Implementation Of MC-QAM Modulator In Digital Television

In this thesis, we analyze the background and features of MC-QAM modulation and show the model of modulation based on quadrature conversion mixer, then present the technology and implementation method for MC-QAM modulation based on the analysis and remark of status. The problems we solved in this thesis include:A procedure to design Root-Raise Cosine (RRC) filters for data transmission application has been described. The proposed algorithm is based on optimal equiripple design technique and the linear equations concluded directly from the requirements of Adjacent Channel Interference (ACI) and Inter-Symbol Interference (ISI). The whole process avoids the numerical ill-conditioning problems because an iterative linear programming technique has been adopted. The two main features that emerge from the proposed algorithm are:(a) ACI reduction, ISI mitigation and lower signal-distortion are obtained, compared to former results. (b) The proposed algorithm is especially favorable for high-order filter designs.A novel architecture for implementing various FIR (Finite Impulse Response) filters expediently in a Field Programmable Gate Array (FPGA) chip has been proposed. The architecture, which utilizes high-speed pipelined Multiple Accumulators, can implement different FIR filters with lowest logic resource usage by considering area-speed tradeoffs. And the base-band shaping filter is taken as example to show how to implement FIR filter with this architecture and compare with the traditional architecture for FIR filter. The result reveals that the restriction of synthesis between the area and speed can be much more efficiently optimized by using the proposed architecture.A method of interpolation filter for arbitrary digital signals sampling rate conversion has been given. The proposed algorithm is based on the conversion-ratio- independent sampling method of interpolation's time-continuous impulse response, optimal equiripple Nyquist FIR Filter and flexible polynomial interpolation. The three main features can be obtained from the proposed algorithm:(a) The Arbitrary Sampling Rate Conversion (ASRC) filter can achieve time-variant sampling rate conversion with fixed structure. (b) Accurate frequency response and maximum- minimum stop-band attenuation can be obtained. (c)Flexible polynomial interpolation can minimize the storage requirement of the whole ASRC filter.A novel multi-carrier QAM model compatible with digital circuit implementation has been presented. The corresponding optimized algorithms, including Opti-Phase-Based Multi-carrier QAM to enhance the output power of each subchannel signal, and the method for high-precision, low-complexity DDFS to synthesize the opti-phase subcarrier waves, are proposed. As a result, spectrum measuring result proves that the multi-carrier QAM model is reasonable and the optimized algorithms improve the output signal quality.An implementation of Universal Asynchronous Receiver/Transmitter (UART) has been suggested. To avoid interference caused by random pulse, we give a useful method to offer better performance by adding digital correlator into the receiver to implement optimum receiving. In addition, it is discussed that how to optimize the logic design of UART according to the structure feature of FPGA. As a result, the UART based on optimum receiving had the increased performance and the decreased logic usage.In conclusion, we propose the further development directions of QAM modulator in Digital Video Broadcasting Cable system (DVB-C).