Research On The Modulation And Demoudulation Of DRM

As a technique which has high bandwidth efficiency and can reduce multipath interference, OFDM is attracting increasing attention in the field of wireless and wire communications, especially in the field of broadcasting. The technique which can overcome frequency-selective fading and have high bandwidth efficiency is needed in order to realize high-quality transfer of voice in the bandwidth of 9 or 10kHz, which is the channel bandwidth of time-varying and multi-path digital amplitude modulated broadcasting (DAMB). Obviously, OFDM is one of the choices inevitably. OFDM and its application in DAMB have been researched systematically in this paper, and the algorithms of synchronizing and channel estimation in a DAMB receiver have been analyzed in detail. Through simulation, the performance of the receiver in different channels has been also compared. The contents in this paper include:At first, the basic theory of OFDM is introduced in Chapter 1, which includes basic structure and the characteristics of time and frequency. In order to describe its theory more clearly, this chapter presents the typical graphs of all parts in OFDM system. Then, the advantages, disadvantages and the key techniques in OFDM have been discussed.The characteristics of the channel in the field of wireless communication are always the difficult part and the focus in researching communication, a right channel model is the crux of constructing and realizing wireless communication systems. At first, Chapter 2 has analyzed the characteristics of coherence and fading in wireless channels, especially the model of multi-path fading; then, the channel characteristics of DAMB has been described and analyzed in detail.According to the standard of DAMB which is formulated by DRM organization, Chapter 3 has introduced the scheme of designing and realzing OFDM in particular.Chapter 4 has analyzed the effects of frequency and time offset on OFDM systems though an OFDM model at first, and then has researched and validated the algorithms of synchronization and channel estimation in DAMB by simulation. At last, the structure of receiver in DAMB has been presented and its performance in different channels simulated.The TMS320C6713 DSP chip of TI has been introduced and its structure, characters and function have been presented in Chapter 5 at first; and then, the scheme of designing and realizing in this hardware platform has been proposed by analyzing the modulation and demodulation of DAMB.Finally, we conclude the whole paper, offer the direction of the field and describe what the author itself has learned.