利用共轭对称性的数字IQ频域校准方法

doi:10.19665/j.issn1001-2400.2021.02.023

摘要/Abstract

摘要：

针对雷达中频信号解调过程中的IQ不平衡问题,从IQ不平衡模型及误差的频谱特点分析出发,提出了基于共轭对称性的数字IQ频域校准方法。首先将存在IQ不平衡的中频信号进行频域分解,展开为单边的理想信号和双边的误差信号,其中误差信号可进一步分解为镜像分量误差和主频分量误差;然后利用两种误差信号的原始频谱和共轭信号频谱的对应关系,在数字端通过频谱运算,得到误差信号的频域估计;最后对中频信号频谱和误差信号频谱估计值进行相减相消,完成校准。合成孔径雷达成像实验结果表明,所提方法可以有效地抑制中频信号的镜像分量误差和主频分量误差,从而有效地校准IQ的幅相不平衡问题。

关键词: IQ不平衡, 雷达信号处理, 误差校准, 合成孔径雷达

Abstract:

To address the problem of IQ imbalance in the demodulation of radar intermediate frequency(IF) signals,this paper proposes a method for digital IQ calibration in the frequency domain based on conjugate symmetry.By modeling the IF signal at the presence of IQ imbalance,its spectral characteristic is first analyzed.The IF signal in the frequency domain can be decomposed into the unilaterally ideal signal and bilateral error signal.Among these,the bilateral error signal can be further decomposed into two components,the mirror-frequency error and the main-frequency error.Then,the relationship between the original spectrum of these two components and the spectrum of their conjugate counterparts is used to conduct some simple calculations for obtaining a frequency-domain estimate of the error signal.Therefore,the estimated error can be used to make the compensation in the IF signal.Experimental results from synthetic aperture radar imaging verify that the proposed method can effectively suppress both the mirror-frequency error and the main-frequency error from the IF signal and calibrate IQ imbalance to achieve the high performance of imaging.

Key words: IQ imbalance, radar signal processing, error calibration, synthetic aperture radar

中图分类号:

TN95

陶毅,丁丽. 利用共轭对称性的数字IQ频域校准方法[J]. 西安电子科技大学学报, 2021, 48(2): 181-189.

TAO Yi,DING Li. Method for digital IQ frequency-domain calibration based on conjugate symmetry[J]. Journal of Xidian University, 2021, 48(2): 181-189.

图/表 8

图1

表1

各参数的取值及含义"

参数名	含义	取值
V₁	含有误差的中频信号的主频分量值	V₂+V₄+V₅
V₂	理想中频信号的主频分量值	A exp(jθ)
V₃	双边总误差信号的主频分量值	V₄+V₅
V₄	实误差信号主频、镜频分量值或双边总误差信号的镜频分量值	0.5A $exp (- j θ) - α exp (- j (φ + θ))$
V₅	复误差信号的主频分量值	A $α cos (θ + φ) - cos θ$

表1

图2

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图7

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