Measurement of Intersymbol Interference Jitter by Fractional Oversampling for Adaptive Equalization

The deterministic jitter due to the intersymbol interference (ISI) is measured on-chip by fractional oversampling, which can be used to adapt the equalization coefficients of a continuous-time linear equalizer. The effective resolution of the jitter measurement is improved to 0.1 unit interval (UI) by sampling the data input by multiphase sampling clocks spaced by 0.7 UI with the proposed fractional oversampling. The ISI jitter measurement technique with the fractional oversampling has been applied to a 4.2-Gb/s mesochronous serial link and implemented in a 0.13-μm CMOS process to prove the concept.