Performance Comparison of QPSK Based Single and Double Stage Digital Interpolators

In this paper, the performance of single stage and double stage digital interpolators has been compared and has been showed that by using multi stage interpolation system the reliability of any communication system increases drastically. Digital signal interpolation systems can be implemented in a variety of ways. The basic interpolator for up-sampling can be a combination of an expander unit with an interpolation low-pass filter in cascade. Complicated implementations can be done by connecting multiple expander and low-pass filter pairs in cascade. This paper presents the efficient implementation of digital interpolation systems for up-sampling of single stage and double stage digital interpolators by using quadrature phase shift keying technique. Comparison is done in terms of spectrum of generated signal, envelope power, modulated signal trajectory, input and output constellation and noise performance.