Rajeev Ratan

Performance comparison of quadrature amplitude modulation (QAM)-based single- and double-stage digital interpolators

In this article, the performance of quadrature amplitude modulation (QAM)-based single- and double-stage digital interpolators have been compared. The basic interpolator for up-sampling can be a combination of an expander unit with an interpolation lowpass filter in cascade. Complicated implementations can be done by connecting multiple expander and low-pass filter pairs in cascade. This article presents the efficient and effective implementation of digital interpolation systems for up-sampling of single- and double-stage digital interpolators. Comparison is done in terms of spectrum of generated signal, envelope power, modulated signal trajectory, input and output constellation and noise performance. In this article, the proposed interpolation filters have been simulated in Agilents Advanced Design System (ADS).

Cubic Lagrange polynomial-based designing of efficient interpolators

Design and implementation of an interpolator with high flexibility and low cost is one of the biggest challenges for modern communication receivers. Some communication receivers require sample rate to be down converted by a fractional factor and Farrow structure is the most competitive candidate for this purpose. However, the existing Farrow structure suffers from the problem of timing control, which limits its potential applications. In this paper, an efficient modified Farrow structure has been proposed and implemented using Lagrange polynomial. An exhaustive analysis has been also presented to calculate the coefficients of the proposed Farrow structure. Simulations have been carried out in MATLAB and the proposed Farrow filter has been implemented on Altera Stratix III EP3SL70F780C2N device for resource comparison.