The Design Of Predistortion Network In Broadband

The wireless channels have the characteristics of time-varying and multipath-fading, and it will cause that the signal has amplitude-phase distortion which is transferred through channels. Aim at the distortion of signals, The thesis studies that design a predistorted network at the transmitter, namely to design a FIR filter to compensate the fading characteristics of the channel, in order to correct the amplitude and phase distortion of channels.With the development of digital signal processing technology, the FIR filters have been used in application more and more widely, the design issues is the focus of researches continuously. There are many existing methods of designing FIR filters, and the mathematical optimization method is a large class. Mathematical optimization is a large class method of solving the optimal solutions by using certain constrained way which is based on the objective function under certain criteria. In this thesis, we will use the frequency response errors and phase response errors constrains to design FIR filter,this constrained way can get a convex feasible region, and can control the amplitude and phase errors independently. The simulations prove the constrained approach is effective.The traditional mathematical optimization methods(including: linear programming,semi-infinite programming and so on) of designing FIR filters can only solve the problem of a particular form, or have lower computational efficiency, especially for the problem of designing complex coefficient filters, and has a poor versatility. Based on this, the thesis will focus on adopting SDP(semi-definite programming) methods to design FIR filters. Compared to other optimization methods, the SDP can accurately solve a large class of convex optimization problem, and some of software has been designed for solving SDP problems, the software can not only achieve higher efficiency but also get great results of solution. Some simulating experiments will prove the effectiveness and flexibility of the SDPTo design a predistorted FIR filter to correct amplitude and phase distortion which is caused by the time-varying multipath-fading channel. And the simulation results show that the method of the study is feasible and effective.