An Adjustable Calibration Technique for Frequency Response Mismatches in TI-ADC System

With the rapid development of electronic information technology, there is a growing need for digital acquisition system to measure with sufficiently high speed. The time-interleaved analog-to-digital converter (TI-ADC) system is a widely used solution, which could achieve high sampling rate while maintaining a high performance at a reasonable power consumption. However, the non-ideal frequency response among channels will introduce frequency response mismatches, which will seriously affect the system to reproduce the original signal, especially for wideband system. The frequency response mismatches are more complicated than the frequency independent mismatches in TI-ADC system, which degrade the system performance severely. In this paper, a multi-channel frequency response mismatches adjustable calibration method is proposed. In order to balance the difference between the sub-channel frequency response and the desired frequency response, the problem of designing the compensation filter is transformed to expanding the frequency response into a polynomial of the digital differentiator. And the least mean square adaptive strategy is used to adjust the polynomial coefficients to minimize the cost function under the nonlinear optimization problem based on cross-correlation. The proposed algorithm used digital post-processing technology to effectively compensate the frequency response of the multi-channel acquisition system and reduce the requirement of hardware resources. The experimental results verify the effectiveness of the algorithm, and the spurious-free dynamic range of system was improved.