The effect of gaussian pulse-shaping filter roll-off factor on the performance of QPSK modulated system

Modern communication system demands special attention to use primary resources like transmitted power and channel bandwidth. Due to optimum requirement of bandwidth and power, the quadrature phase shift keying (QPSK) is well suited for different applications in mobile as well as satellite communication. Proper pulse shaping technique makes a digital communication system possible to transmit data within a limited bandwidth with a minimum value of inter symbol interference (ISI). In this paper we have presented the measurement results of some useful performance parameters of QPSK system like, error vector magnitude (EVM), signal to noise ratio (SNR) and bandwidth efficiency with respect to roll-off factor (alpha) of Gaussian pulse-shaping filter. The effect of Gaussian filter alpha on system ISI has been studied by recording the eye diagram of the system. The performance of the Gaussian filter has also been compared with other conventional pulse-shaping filters like, raised cosine and root raised cosine filter.