A Novel Iterative Structure for Online Calibration of $M$-channel Time-Interleaved ADCs
A Novel Iterative Structure for Online Calibration of $M$-channel Time-Interleaved ADCs
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DOI：
10.1109/tim.2013.2278574
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发表时间：
2014-02
影响因子：
5.6
通讯作者：
K. Tsui;S. Chan
中科院分区：
文献类型：
--
作者：
K. Tsui;S. Chan
本文提出了一种计算效率高的校准结构，用于在线估计和补偿M通道时间交织（TI）模数转换器（ADC）中的失调、增益和频率响应失配。所提出的方法的基本思想是保留一些采样时刻，用于估计和跟踪子ADC的失配参数与已知的输入。由于估计问题类似于一个标准的系统辨识问题，我们提出了两个简单的可变数字滤波器（VDF）的自适应滤波器结构，这是来自最小均方（LMS）和归一化LMS算法。另一方面，在TI ADC的正常操作中保留一些采样时刻意味着必须牺牲部分样本。基于一般时变线性系统模型的失配和频谱特性的一个轻微的过采样输入信号，我们还提出了一种新的迭代框架来解决由此产生的欠定问题。它不仅包含了一些迭代算法的收敛速度和算法复杂度之间的权衡，但也承认有效的更新结构的基础上再次VDFs。因此，由于VDF的众所周知的高效实现，估计和补偿算法的适应性允许我们将它们无缝地结合起来，以形成在线校准结构，该结构能够以低复杂度和高重建精度跟踪和补偿通道失配。最后，我们通过计算机模拟证明了所提出的方法的实用性。
This paper proposes a computationally efficient calibration structure for online estimation and compensation of offset, gain and frequency response mismatches in M-channel time-interleaved (TI) analog-to-digital converters (ADCs). The basic idea of the proposed approach is to reserve some sampling instants for estimating and tracking the mismatch parameters of sub-ADCs with reference to a known input. Since the estimation problem is analogous to a standard system identification problem, we propose two simple variable digital filter (VDF) based adaptive filter structures which are derived from the least mean squares (LMS) and normalized LMS algorithms. On the other hand, the reservation of some sampling instants in the normal operation of TI ADC implies that part of samples have to be sacrificed. Based on a general time-varying linear system model for the mismatch and the spectral property of a slightly oversampled input signal, we also propose a novel iterative framework to solve the resulting underdetermined problem. It not only embraces a number of iterative algorithms for the tradeoff between convergence rate and arithmetic complexity but also admits efficient update structure based again on VDFs. Therefore, thanks to the well-known efficient implementation of VDFs, the adaptability of both estimation and compensation algorithms allows us to combine them seamlessly to form an online calibration structure, which is able to track and compensate for the channel mismatches with low complexity and high reconstruction accuracy. Finally, we demonstrate the usefulness of the proposed approach by means of computer simulations.