A fast Fourier transform based method to estimate frequency response mismatches in time interleaved systems

Area of Science:

• Electrical Engineering
• Signal Processing
• Analog-to-Digital Conversion

Background:

• Time interleaving (TI) is crucial for high sampling rates in acquisition systems.
• TI systems suffer from channel mismatches (offset, gain, time) that degrade performance.
• Gain and time mismatches are frequency-dependent, complicating system calibration.

Purpose of the Study:

• To propose and analyze a frequency response mismatch estimation method for TI systems.
• To address mismatches in TI analog-to-digital converters (ADCs) where analog bandwidth exceeds single-channel sampling rate.
• To calibrate identified mismatches to improve overall system performance.

Main Methods:

• Compared mismatch models to establish the relationship between frequency response and gain/time mismatches.
• Utilized sinusoids at various frequencies to estimate mismatch coefficients.
• Developed a semi-automatic estimation technique and implemented it on a 10 GSPS, eight-channel TI system.

Main Results:

• Simulations demonstrated the accuracy and effectiveness of the proposed frequency response mismatch estimation method.
• Calibration using estimated parameters significantly improved system performance.
• Spurious Free Dynamic Range (SFDR) increased from 27.66 to 56.70 dB; Signal-to-Noise Ratio (SNR) improved from 25.55 to 32.77 dB.

Conclusions:

• The proposed method accurately estimates frequency response mismatches in TI acquisition systems.
• Calibration based on these estimations effectively enhances TI system performance.
• The technique is valuable for improving the fidelity of high-speed data acquisition systems.