Audio Filter, Filter Bank Design Study

Wireless communication has played a more and more important role in peoples' daily life with the development of semiconductor and computer technologies in recent decades, which in turn promote the rapid expansion of the wireless communication.The definition of the next generation of mobile communication is the new emphasis of research with the rapid increase in sound, image and data communications over the internet and wireless. The demand on data rate in this broadband wireless communication system will exceed several Mbps, which means the delay time of the delayed waves will become greater than one symbol time and a larger bandwidth is needed. So it is important to transmit data over band limited channel in a high data rate reliably.High data rate in wireless communication is limited by additive noise and the Inter-symbol Interference (ISI) owing to multipath propagation. When the data rate is more than several Mbps, there is ISI because the signal duration is shorter than the channel delay spread. In conventional single-carrier modulation, the system complexity will increase greatly due to the multi-taps equalizer used in high data rate wireless communication. The effects of the ISI are negligible so long as the delay spread of the multipath channel is significantly shorter than the duration of one transmitted symbol. So multi-carrier transmission technology can be used to overcome this limitation.Nowadays, Orthogonal Frequency Division Multiplexing (OFDM) is a key technology in the mobile communication field. As one of the multi-carrier transmission technologies, OFDM can reduce the multipath fading effect with high frequency efficiency. However there are some disadvantages in OFDM system such as sensitivity to frequency offset, symbol synchronization and so on. All of these limit the application of OFDM in wireless environment.Filtered Multitone (FMT) Modulation is a new multicarrier technology incontrast to OFDM. In FMT system, the spectrum of each subchannel has a high level of spectral containment. So the Inter-channel Interference (ICI) of FMT is negligible compared to other noise, while it often appears in OFDM system because of its sensitivity to frequency offset. However, subchannel equalization is needed in order to reduce the remaining ISI introduced by the filter banks.In this thesis we introduce the filter bank based multicarrier (FB-MC) transmission technology and give the practical efficient implementation structure. In the following, we introduce the principle of OFDM and FMT technology in filter bank view point.In the chapter 3, we analyze the basic theory of filter bank modulation in FMT emphatically, and do research on the design of prototype filter. Several indice and methods for design of filter are derived. At the end, the simulations of the performance of the prototype filters designed by the methods in wireless environment are studied. The simulation results imply that FMT technology still has good performance in wireless environment.The chapter 4 of the paper studys the optimization of filter bank and the prototype filter. We can get better performance of system by optimizing the indice of prototype filter. The simulation result shows the effect of the optimization of prototype filter.Because of the limitation of the time and some objective conditions, we only simulate parts of the design of the prototype filter. And there are many topics which are not studied including other optimization design, for example, to get the largest achievable bit rate, there is trade-off between the subchannel spectral containment between ISI. We will further our study in later days.