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Keywords
(7)
Fir Filter
Frequency Dependence
Frequency Estimation
Frequency Offset
Nonlinear Least Squares
Direct Conversion Receiver
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Frequency offset and I/Q imbalance compensation for OFDM directconversion receivers
Frequency offset and I/Q imbalance compensation for OFDM directconversion receivers,10.1109/ICASSP.2003.1202741,Guanbin Xing,Manyuan Shen,Hui Liu
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Frequency offset and I/Q imbalance compensation for OFDM directconversion receivers
(
Citations: 20
)
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Guanbin Xing
,
Manyuan Shen
,
Hui Liu
Two types of RF frontend imperfections in directconversion receivers, namely
frequency offset
and I/Q imbalance, are addressed. The I/Q imbalance not only introduces an unwanted image interference, but also degrades the accuracy of carrier estimation. We propose a pilotbased scheme for both
frequency offset
and I/Q imbalance compensation. A
nonlinear least squares
(NLS) frequency estimator, robust to the I/Q imbalance, is developed. Also derived is an I/Q compensation structure that consists of two stages: the frequency dependent imbalance is compensated with an
FIR filter
whereas the frequency independent part is corrected with an asymmetric phase compensator. The compensation coefficients are optimized by restoring the phase rotation embedded in the pilot symbols.
Conference:
International Conference on Acoustics, Speech, and Signal Processing  ICASSP
, vol. 4, pp. IV70811 vol, 2003
DOI:
10.1109/ICASSP.2003.1202741
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Citation Context
(14)
...In [
7
], an algorithm for I1Q imbalance compensation in the presence CFO was proposed...
...CFO and I/Q imbalance in field programmable gate array (FPGA), and then we used the algorithm in [
7
] as Implemented system uses the 7r/4 differential quadrature phase shift keying (7r/4DQPSK) wireless communication system...
Takuro Yoshida
,
et al.
FPGA implementation of joint CFO and IQimbalance compensator for narr...
...Several articles on static and dynamic description of the imbalance effects for the modulator [2], [3] and the demodulator [4], [5], [
6
] can be found...
...Using the same naming convention as in the foregoing section the frequency domain representation of the linear IQdemodulator output signal is given by [4], [
6
]:...
Michael E. Gadringer
,
et al.
Comparison of the imbalance effects in direct conversion transmitters ...
...Fortunately, a number of methods have already been shown to reduce I/Q imbalance with varying effectivity and complexity [
38
]...
...In [
7
], an algorithm for I/Q imbalance compensation in the presence of CFO was proposed...
...In [8], an improvement was proposed based on [
7
] which removes the spectral search based CFO estimation...
...Simulation results show that our proposed algorithm has better CFO accuracy compared to [
7
] and [8] and can completely remove I/Q imbalance based on its BER performance...
...Details on this system model can be found in [
68
] and references therein...
...This architecture is mainly to aid in the algorithm derivation and can be shown to be equivalent to the architectures in either [
7
] or [8]...
...This compensation structure reduces the parameters estimated by letting the frequency independent I/Q imbalance parameters be absorbed by the compensating filter w .T he consequence is that compared to the compensating filter in [
7
], our compensating filter is complex valued...
...Our proposed algorithm similar to [
7
] and [8] assumes that a Plength training sequence consisting of M Nlength short symbols is transmitted and used to estimate CFO and I/Q imbalance...
...The derivations for CFO and I/Q imbalance assumes that a minimum amount of CFO is present for stability just like [
7
] and [8]...
...Since the bulk of the computations for all algorithms is in the compensating filter pseudoinverse step except possibly for [
7
], the proposed algorithm saves a lot of complexity by having smaller matrix for this step...
...Note that while the proposed algorithm operate on complex valued matrices, the added complexity is still much lower compared to [
7
] or [8] where the LLS matrix rank is one and two higher respectively...
...It was however modified to follow (25) when used for the proposed algorithm and [8] while for [
7
], the preamble was modified to follow its own proposed structure...
...For [
7
], which estimates the CFO via a line search, we limited the search to [.48 .48] with a resolution of 0.001...
...Case A � Proposed Case B � Proposed Case A � [
7
] Case B � [7] Case A � [8] Case B � [8]...
...Case A � Proposed Case B � Proposed Case A � [7] Case B � [
7
] Case A � [8] Case B � [8]...
...Case A � Proposed Case B � Proposed Case A � [
7
] Case B � [7] Case A � [8] Case B � [8] NO CFO/IQ...
...Case A � Proposed Case B � Proposed Case A � [7] Case B � [
7
] Case A � [8] Case B � [8] NO CFO/IQ...
...This is due to the different compensation structures in [
7
],[8], and the proposed algorithm...
...It is clear from the figure that the proposed algorithm along with [8] can effectively eliminate case A and case B I/Q imbalance whereas as mentioned in [8], [
7
] has a high BER floor in case B due to inexact signal convolutional structure with the frequency selective I/Q imbalance...
Leonardo Lanante Jr
,
et al.
Low complexity compensation of frequency dependent I/Q imbalance and c...
...1) Dataaided (DA) methods, in which special pilots and training symbols are inserted into the transmitted data [
3
, 4]. 2) Nondataaided (NDA) methods, in which the transmitted data are used without any other additional information [5, 6]. 3) Adaptive FIR filter based methods, in which the received databeforetheFFTareutilizedtohandleestimation,were presented to certify for an Image RejectionRatio (IRR) of 75–97 dB after compensation...
...The I/Q imbalance with filter mismatch, namely frequencydependent I/Q imbalance, is much critical for OFDM directconversion receivers to make the corresponding estimation and compensation be extremely difficult [
3
, 9]...
...Simulations of a 2×2 MIMOOFDM system indicate that the proposed approach results in a 1.2dB SNR loss with ideal channel estimations to achieve 50dB IRR and 8% PER at frequencydependent I/ Q imbalance with a gain error of 1 dB, a phase error of 10° and the worst FDI of 180° [
3
]...
...Figure 4 displays the model of frequencydependent I/Q imbalances [
3
]...
...The basic model [11, 12] is a special case of HI ðf Þ¼ HQðf Þ ,w hereaðf Þ¼ 1 þ ge � jq ðÞ = 2a ndbðf Þ¼ 1 � ge jq ðÞ =2. Figure 5 plots the channel frequency response (CFR) influenced by frequencydependent I/Q imbalance with 1dB gain error, 10°phase error & 20°phase error, and 180°filter mismatch [
3
], in which FDI induces highfrequency ...
...c) The worst FDI: 180°filter mismatch [
3
]...
...Ref [
3
] Ref [4] Ref [5] Ref [6] Ref [7] Ref [8] Proposed work...
WeiChi Lai
,
et al.
CrossValidation Estimation for FrequencyDependent I/Q Imbalance in M...
...OFDM systems have been an active area of research [5][
9
]...
...The authors claimed that this algorithm aside from providing better accuracy, it is also computationally simpler compared to the earlier proposed algorithm in [
9
]...
Leonardo Lanante Jr
,
et al.
A Simple Estimation Scheme for Joint Estimation of Carrier Frequency O...
References
(4)
Adaptive compensation for imbalance and offset losses in direct conversion transceivers
(
Citations: 139
)
J. k. Cavers
,
M. w. Liao
Conference:
Vehicular Technology Conference  VTC
, 1993
Carrier Frequency Offset Estimation for OFDMBased WLANs
(
Citations: 99
)
Jian Li
,
Guoqing Liu
,
Georgios B. Giannakis
Journal:
IEEE Transactions on Signal Processing  TSP
, 2001
OFDM for Wireless Multimedia Communications
(
Citations: 1582
)
R. Van Nee
,
R. Prasad
Published in 2000.
Analysis of IQ imbalance on initial frequency offset estimation in direct downconversion receivers
(
Citations: 11
)
V. K.P. Ma
,
T. Ylamurto
Conference:
IEEE Workshop on Signal Processing Advances in Wireless Communications  SPAWC
, 2001
Sort by:
Citations
(20)
FPGA implementation of joint CFO and IQimbalance compensator for narrowband wireless system
Takuro Yoshida
,
Daisuke Nojima
,
Yuhei Nagao
,
Masayuki Kurosaki
,
Hiroshi Ochi
Conference:
International Conference on Advanced Technologies for Communications  ATC
, pp. 327332, 2011
Comparison of the imbalance effects in direct conversion transmitters and receivers
Michael E. Gadringer
,
Thomas Faseth
,
Gottfried Magerl
Conference:
International Workshop on Integrated Nonlinear Microwave and Millimeterwave Circuits  INMMIC
, 2011
Low complexity compensation of frequency dependent I/Q imbalance and carrier frequency offset for direct conversion receivers
(
Citations: 1
)
Leonardo Lanante Jr
,
Masayuki Kurosaki
,
Hiroshi Ochi
Conference:
IEEE International Symposium on Circuits and Systems  ISCAS
, pp. 20672070, 2010
CrossValidation Estimation for FrequencyDependent I/Q Imbalance in MIMOOFDM Receivers
WeiChi Lai
,
TaYang Juan
,
TerngYin Hsu
,
ShengLun Chiou
Journal:
Journal of Signal Processing Systems  JSPS
, vol. 60, no. 1, pp. 5970, 2010
I/Q Imbalance Compensation Using a Nonlinear Modeling Approach
(
Citations: 9
)
Haiying Cao
,
Ali Soltani Tehrani
,
Christian Fager
,
Thomas Eriksson
,
Herbert Zirath
Journal:
IEEE Transactions on Microwave Theory and Techniques  IEEE TRANS MICROWAVE THEORY
, vol. 57, no. 3, pp. 513518, 2009