A 2-way interleaving 3-tap analog feedforward equalization for high-speed analog multiplexing

Abstract

With the rapid growth of data traffic, there is an increasing demand for larger bandwidths in fixed networks. The transmitter bandwidth extension is usually achieved by combining analog multiplexers (AMUX) with digital-to-analog converters (DAC) designed in CMOS. Additionally, feedforward equalization (FFE) is incorporated at the high-speed front-end. However, this adds complexity and significant power consumption. In this work, we describe an alternative FFE approach that reduces the complexity of power-hungry high-speed front-ends, thereby improving power efficiency. This approach uses a 28 nm CMOS chip that sends two outputs with FFE predistorted data at 40/80 Gbps NRZ/PAM4. When combined with an AMUX, it generates equalized eye diagrams at 80/160 Gbps NRZ/PAM4 after a channel model with an insertion loss of 8.4 dB at 40 GHz, with a voltage swing of 100 mVpp,diff/190 mVpp,diff, while dissipating 0.889 W of power (5.56 pJ/bit).