Digital pulse-shaping FIR filter design with reduced intersymbol and interchannel interference

An important requirement in the design of data transmission filters is the minimization of intersymbol interference, which is zero if the overall impulse response (transmit filter, channel and receive filter) satisfies the first Nyquist criterion. In this context, an important class of transfer functions, satisfying the Nyquist criterion, is the raised-cosine filter family. In order to guarantee low interference between adjacent channels, the transmit and receive filters must have a high value of stopband attenuation, so as to reduce the interchannel interference as much as possible. In this paper, a design method for finding the coefficients of a pair of linear-phase transmit/receive FIR filters, that when cascaded have raised-cosine frequency response, is presented. The design is based on Frequency Sampling techniques, and the filter parameters are chosen in order to obtain maximum stopband attenuation and low intersymbol interference. The filter coefficients can be easily evaluated and the optimal filter parameters can be obtained with tables or equations. The design method is very simple, completely automatic and suited for non-filter-oriented users. Look-up table techniques can be used for automatic re-design of the transmit and receive filters, making the proposed solution well suited to programmable computing platforms (FPGA—Field Programmable Gate Arrays- and PLD---Programmable Logic Devices-based platforms), or for applications where the design must be performed without any user intervention. The proposed filter design technique is quite simple and the results obtained often match the performance of filter designed using computationally more complex and conceptually more difficult methods. Copyright © 2003 AEI.