A quadrature clock generator with calibration for 22∼31.4 GS/s real-time sampling system

This paper presents an accurate quadrature clock signals with phase calibration for ultra-high speed real-time sampling system. The proposed four-phase clock generator is a phase locked loop (PLL) with a novel quadrature divider which can realize tunable quadrature phase to calibrate variable mismatches. The operating frequency of the proposed quadrature clock can be tuned from 5.5GHz to 7.85GHz which can be used in four-channel time-interleaved sampler. The real-time sampling system achieve 28-31.2GS/s sampling rate. The chip consumes 28mW power with 1.2V supply voltage in TSMC 65 nm CMOS process. The measurements show that the calibration phase can cover ±10°I phase and Q phase mismatch. The phase noise is -115 dBc/Hz@1MHz offset frequency at 6.85GHz center frequency and cycle-to-cycle time RMS jitter is 210fs.