Joint Estimation of IQ Imbalance and Channel Response for Wideband Communication Systems
Date Issued
2006
Date
2006
Author(s)
Chang, Ting-Kang
DOI
en-US
Abstract
Nowadays, a lot of effort is spent on developing inexpensive OFDM receivers. Especially, zero-IF receivers are very appealing, because they avoid costly IF filters.
However, zero-IF front-ends also introduce significant additional front-end distortion, such as IQ imbalance. Unfortunately, OFDM is very sensitive to nonidealities (IQ
imbalances) in the receiver front-end. An important effect of IQ imbalances is that achievable BER saturates as the SNR increases, suggesting that the system’s performance
at high SNR will be dominated by the IQ imbalances rather than the operating SNR. In this thesis, the effect of IQ imbalances on OFDM receivers is studied, and a framework for deriving OFDM receivers with IQ imbalance correction in the digital domain was presented. We propose three new schemes for joint IQ imbalance compensation and channel estimation. Previous method is sensitive to channels with
nonflat frequency response. Besides leading to performance enhancements, our approaches are robust against channels with highly nonflat frequency response with low complexity. Additionally, one or two OFDM training block provides sufficient information to accurately estimate the IQ imbalances and the channel response, allowing to shorten the training time. Therefore, our methods greatly relaxes the mismatch specifications and thus enable zero-IF receivers employing cheap analog components.
Subjects
實虛部非協調
正交分頻多工系統
前置迴旋碼單載波系統
IQ imbalance
OFDM
SC-CP
Type
thesis
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