High sampling speed can be achieved using multiple Analog-to-Digital Converters (ADCs) based on the Time-Interleaving A/D Conversion (TIADC) technique. Various types of methods were proposed to correct the mismatch errors among parallel ADC channels in TIADC systems, which would deteriorate the system performance. Traditional correction methods based on digital signal processing have good performance, however often only for input signals limited in a narrow frequency band. In this paper, we present our recent work on design of an 8-Gsps 12-bit TIADC system and implementation of real-time mismatch correction algorithms in FPGA devices, over a broad band of input signal frequencies. Tests were also conducted to evaluate the systems performance, and the results indicate that the Effective Number of Bits (ENOB) is enhanced to be better than 8.5 bits (<800 MHz) and 8 bits from 800 MHz to 1.6 GHz after correction, almost the same with that of the ADC chip employed. Index Terms-time-interleaved technique, high-speed high-resolution A/D conversion, mismatch errors, real-time correction algorithms, broad band. I. INTRODUCTION AVEFORM digitization is a preferable solution in physics to obtain the most detailed information from the signals out of detectors, and has thus been employed in many physics experiments [1]-[11]. With the development of electronics, especially ASIC design on Analog-to-Digital Converters (ADCs), sampling speed has been increasing. With the Time Interleaved A/D Conversion (TIADC) technique, the system sampling speed can be greatly enhanced beyond single ADC ASIC's capability [8]-[10], which makes the study in this direction a research hot spot.

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A time-interleaved analog-to-digital converter (TI-ADC) uses several sub-analog-todigital converters (sub-ADCs) to achieve a high sampling rate. Its applications include communication systems, oscilloscopes, healthcare instruments, etc. However, the presence of sub-ADC channel mismatches such as offset, gain and sample-time mismatches can significantly degrade the performance of TI-ADCs. This paper proposes a fully digital foreground calibration technique for the TI-ADC, including mismatch correction and estimation blocks. Unlike existing techniques, the proposed technique requires low computational resources. As the resource for complex computing in a field-programmable gate array (FPGA) is mainly the digital signal processor (DSP), the mismatch correction block unifies each computing unit in the FPGA into a multiply adder to achieve low DSP consumption. To further reduce the use of DSP resources, the selection of an optimal number of taps of the finite impulse response filter used for mismatch correction is discussed. The optimal-tap filter that uses the lowest amount of DSPs while satisfying the required signal-to-noise and distortion ratio flat area bandwidth is presented. A real-time hardware correction block was implemented for an 8 Gs/s TI-ADC system with two sub-ADC channels, and the results with this hardware verify the low computing resource consumption feature of the proposed calibration technique.

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