Coherent RF transceiver for broadband waveguide links assisted by baseband phase locked loop

Abstract

This paper presents an 86.71875GHz RF transceiver IC featuring a fully integrated clock and data recovery (CDR)-assisted carrier recovery loop (CRL) with on-chip clock generation for waveguide links. The test chip fabricated in 28nm CMOS demonstrates 57.8125Gb/s PAM-4 data transmission over a 1.5m waveguide channel and 28.90625Gb/s NRZ data transmission over a 3m waveguide channel. The proposed CRL is implemented only by using a base-band CDR without using power-and-area-hungry RF circuit blocks due to the baseband-synchronized carrier frequency in which means an LO frequency is three times the null frequency of the baseband signal. The CDR-assisted CRL improves the measured timing margin of the recovered 28.90625Gb/s NRZ signal at a bit error rate (BER) of 10$^{-12}$ by more than 38% compared to the conventional case. Thanks to the small hardware overhead of the all-digital baseband circuity in the proposed CRL, the proposed link achieves an FoM of 3.5pJ/b/m showing state-of-the-art performance in terms of throughput-distance, and energy efficiency.