Blind Frequency-Dependent I/Q Imbalance Compensation for Direct-Conversion Receivers

I/Q Imbalance Estimation for Direct Conversion Receivers by Jointly Using the Existing Preambles and Blind Estimation

“…δ k1,k2 = 1 if k 1 = k 2 , and δ k1,k2 = 0 otherwise. Unlike the frequency domain estimation method in [7], we do not impose any constraint on the the received symbol power. In the proposed estimation method, E{|H[k]S[k]| 2 } does not need to be the same for different subcarrier indices k. From (7), a linear combination of the received symbols of subcarrier pairs is given by…”

“…According to (7), the effect of I/Q imbalance is regarded as a linear transform on the received symbols on each image subcarrier pair. Consequently, the I/Q imbalances can be compensated by a linear transform on the received symbols on every image subcarrier pair.…”

“…There is a growing interest in the estimation of I/Q imbalances without using on-chip loopback or exclusive pilot signals [7]- [10]. A frequency domain blind estimation method was presented in [7] based on a time-varying wide-sense stationary uncorrelated scattering (WSSUS) channel model.…”

“…A frequency domain blind estimation method was presented in [7] based on a time-varying wide-sense stationary uncorrelated scattering (WSSUS) channel model. By averaging over a time interval much larger than the coherence time, the channel gains become constant across all subcarriers due to the WSSUS property, and therefore, the authors implicitly assumed constant received power across all the subcarriers in [7]. In [8], a blind compensation method for the I/Q imbalance was developed by minimizing the kurtosis of the received symbols.…”

Baseband I/Q regeneration Method for Direct Conversion Receiver to nullify effect of I/Q mismatch

“…[ 15] u ses t he statistical i ndependence b etween t he desired s ignal a nd its mirror im age f or f requency independent I/Q mismatch compensation in lo w-IF receiver by blind signal separation. In [16] a g radient descent search method i n t ime do main a nd a f requency do main a pproach based o n a s ingle-tap matrix i nversion for f requency dependent I /Q i mbalance c ompensation is pr esented. [ 17] provides ad vanced b lind s ource s eparation t echniques f or frequency i ndependent I /Q i mbalance co mpensation i n MIMO s ystems a nd [ 18] s hows t he s ame for t he frequency dependent cas e b y u sing h igher-order s tatistics in a n independent c omponent a nalysis.…”