Performance of a direct conversion receiver with pi /4-DQPSK modulated signal

Abstract

Analog implementation of direct conversion receivers suffers from a variety of detriments such as DC offset, which can be caused by the self-mixing of on and off channel signals, carrier feedthrough from high local oscillator signals, and phase and gain imbalance in the in-phase and quadrature-phase branches. The performance of a direct conversion receiver is investigated. The performance degradation due to various impairments is discussed, and simulated and measured results are compared. Imperfections in the receiver front end as well as degradations due to spurious signals are studied. Signal-to-noise penalty curves for four specific imperfections are presented and possible solutions are recommended to minimize their effects. The results presented are based on a raised cosine Nyquist channel with a roll-off of 0.35.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>