Dmb-t Channel Modulation Of The Fpga-based Design Research

With the development of technology and the progress of our society, digital television has been the mainstream of the modern TV technology. Taken the advantage of the Olympic year, it is with great meaningness to research and promote the digital television and broadcast. Aug 2007, our country formulated the Digital Media and Television Broadcast (DMB), which established ourselve technical standard. Depended on this standard, we develop digital TV which hold ourself independence knowledge property right, thus we can not only afford satisfaction to the increasingly material and cultural requirement of most public poeple, but also impulse forward the associated property.This dissertation firstly formulates and designs the modulation system of DMB-T based on researching the DMB-T's national standard deeply, then designs and simulates the star graph mapping module, the insertion of system information module, the processor of frame-body data, the frame form with inserting PN sequences and the shaping filter which are verified.TDS-OFDM (Time Domain Synchronous Orthogonal Frequency Division Multiplexing) with 3780 carries is one of the key technologies of the DMB-T's modulation system. Because the number of carrer wave is not the integer power of 2, we cannot use the maturational radix-2 and radix-4 FFT algorithm in consideration of the realization effectivity. Aiming at the typical 3780-point IFFT, the subject deeply analyses and compares the speciality and capability of Cooley-Tukey, Winograd and Prime Factor Algorithm. Considering the complexity and algorithm, the speed of calculation, the consumption of resource, we design a new algorithm using the advantage of three kinds of algorithm synthetically. After that, we verify it by Matlab and carry out imitation based on FPGA. By analysis it is cleared that the number of addition and multiplication of the algorithm closes to the 4096-point FFT.The baseband shaping filter of DMB-T system is a Square-root-raised-cosine roll-off FIR filter. Because of the punitive roll-off coefficient that equals 0.05 in realization, it is a key point in this design. By Matlab this subject designs a 169-order equiriple linear-phase digital FIR filter whose stop-band attenuation gets to 46.9 dB, and it completely confirm to the requirement of standard. We realize an I-Q-combined filter using fourfoldness interpolation method on FPGA, carry out design optimization, in order that remarkably bring the operation of filter down and greatly decrease the multiplier resource which the filter needs.