Design of FIR Filter Using Differential Evolution Optimization & to Study its Effect as a Pulse-Shaping Filter in a QPSK Modulated System

In order to reduce the effect of Inter Symbol Interference (ISI) in a digital communication system, different types of transmitting pulse shaping filter has been extensively used in practice. We need to design these filters with some constraints imposed by requirements of the communication system in which we are going to use them. The use of different optimization technique, such as Genetic Algorithm (GA), Particle Swarm Optimization (PSO), has been proved to be quite useful towards the design of those digital filters with certain specifications. In this paper, we have proposed a linear phase FIR digital filter, which has been designed using Differential Evolution (DE) algorithm. The performance of the proposed filter has been examined by recording the variation of the resulting frequency response with number of iteration and population size. The convergence behavior of the optimization technique has also been studied. In addition, the proposed FIR filter has been used as a pulseshaping filter in a Quadrature Phase Shift Keying (QPSK) modulated system and its performance has been evaluated in terms of some system parameters like Error Vector Magnitude (EVM), Signal to Noise Ratio (SNR) and Waveform Quality Factor (ρ). The Eye diagram of the system has also been presented for the proposed filter along with the standard filters like, Raised Cosine (RC) and Root Raised Cosine (RRC) to study the impact of these filters on system ISI.