RE FRONT-END IMPAIRMENT ALLEVIATION IN OFDM TRANSCEIVER SYSTEMS

Abstract

A direct conversion architecture is a simple architecture because of its less number of o - chip components and lower cost in comparison to super-heterodyne architecture. How- ever, direct-conversion architecture su ers from IQ imbalance and Carrier Frequency O set (CFO) which degrades the performance signi cantly, and hence the signal quality is reduced. In this thesis, impact of IQ imbalance and CFO is jointly modeled and analyzed on OFDM systems. IQ imbalance is assumed at transmitter as well as receiver side. The simulation results in this thesis show that the impairments in Zero-IF receivers can have a severe e ect on the symbol error rate (SER). Furthermore, digital baseband algorithms such as least squares (LS), least mean square (LMS) is used to tackle the e ect of IQ im- balance plus carrier frequency o set (CFO) and a digital baseband technique is proposed to enhance the operating signal to noise ratio (SNR). The algorithms are used to com- pensate for the impairments at the transmitter as well as receiver side. A comparative analysis of di erent algorithms is carried out.