Dual-mode non-return-to-zero (NRZ)/ four-level pulse amplitude modulation (PAM4) receiver with digitally enhanced NRZ sensitivity

摘要

A four-level pulse amplitude modulation receiver has a four-level pulse amplitude modulation mode and a non-return-to-zero modulation mode. First, second, and third four-level pulse amplitude modulation samplers are coupled to an input. Each of the samplers has a corresponding output in turn including a corresponding binary decision of the first, second, and third samplers. A four-level pulse amplitude modulation decoder circuit has inputs coupled to the outputs of the samplers. The four-level pulse amplitude modulation decoder circuit is active in the four-level pulse amplitude modulation mode. The receiver also includes a non-return-to-zero majority voting circuit coupled to the outputs of the samplers. The non-return-to-zero majority voting circuit has an output and is configured to output a majority decision of the corresponding binary decisions of the samplers, and is active in the non-return-to-zero modulation mode.