An Adaptive PAM-4 Analog Equalizer With Boosting-State Detection in the Time Domain

This paper introduces an improved adaptive analog equalizer that is required in high speed serial receivers using four-level pulse amplitude modulation signaling. By performing boosting-state detection in the time domain, the proposed adaptive analog equalizer can effectively overcome a serious problem that the received signal’s eye-opening tends to be compromised by the convergence accuracy of the adaptive control loop. To suppress the pattern-dependent jitters (PDJs), an inductor-less, cross-stage feedback structure is employed in the proposed analog equalizer to help broaden its effective tuning bandwidth. Multichannel simulations have confirmed that the proposed equalizer is able to achieve a 42% improvement in eye-height opening when compared with the equalizers employing popular spectrum-comparing schemes. Trellis diagram analyses under different date rates have revealed that the bandwidth of the proposed equalizer can be extended by as much as 60%, thus effectively bringing the PDJs from 44% down to 27.5%.

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