Offset-injection digital background calibration for VCO-based ADC

A new offset-injection digital background calibration technique for VCO-based ADC is proposed to compensate for VCO nonlinearity. By injecting a predetermined offset signal, the new technique suppresses in-band distortions caused by VCO nonlinearity successfully. The offset-injection technique draws support from orthogonal polynomials least mean square algorithm to improve the computation efficiency. A dual-path all-standard-cell VCO-based ADC is also proposed to inject the calibration signal. The proposed VCO-based ADC achieves 71.9 dB of signal to noise and distortion ratio and 11.65 bits of effective number of bit.