Time-interleaved analog-to-digital converter (TI-ADC) technology can increase the sampling rate without changing resolution. But, the dynamic performance of TI-ADC system is seriously deteriorated by channel mismatches. Under the condition of large bandwidth, gain mismatch and timing mismatch vary with the frequency, which cannot be regarded as fixed values. To improve the dynamic performance of the TI-ADC system, an automatic calibration method of channel mismatches for wideband TI-ADC system is proposed in this article. Frequency-dependent channel mismatches are estimated by the algorithm based on sine fitting, and compensated by the means based on perfect reconstruction. The entire sampling and calculation process is automated and tedious operation is simplified. A 6.8-GS/s 12-bit wideband TI-ADC system is implemented. This sampling system can achieve SNDR (signal-to-noise and distortion ratio) above 49 dB and SFDR (spurious-free dynamic range) above 57 dB for an input signal from 100 MHz to 3300 MHz. The proposed calibration method improves the SNDR over 10 dB and the SFDR over 15 dB. The dynamic performance of the sampling system is close to that of its sub-ADC.

The wideband echo signals of the imaging radar can be processed by pulse compression to obtain high-resolution range profile (HRRP). The resolution of HRRP is proportional to the signal bandwidth. The pursuit of high resolution makes the bandwidth of radar transmitting signal larger and larger. And the corresponding sampling rate of receiver becomes so high that analog-to-digital conversion cannot be realized by a single chip correctly. Time-interleaved analog-to-digital converter (TIADC) technique increases sampling rate of radar receiver, but channel mismatches are brought in. Channel mismatches significantly deteriorate the dynamic performance of radar receiver. Effects of channel mismatch on SNR, SNDR and SFDR are studied in previous literatures. Derivation and simulation of TIADC channel mismatch effecting on HRRP are performed in this letter. Simulation results show that without considering the amplitude-frequency distortion and phase-frequency distortions of the radar system, when the gain mismatch is less than 0.7 times and the clock mismatch is less than 0.25 rad, the influence of the channel mismatch on the HRRP can be neglected. The results provide a reference for system design and compensation method, which are useful for the designer to determine whether complex channel mismatch calibration is necessary under specific application background.