A Power-Efficient 20–35-GHz MZM Driver With Programmable Linearizer for Analog Photonic Links in 28-nm CMOS

Abstract

Analog photonic links require linear drive of electrooptic modulators at high frequency to support emerging millimeter wave (mm-wave) communication standards. However, this is challenging due to the nonlinear distortion of commonly used Mach–Zehnder modulators (MZMs). This article presents the first CMOS MZM driver capable of operating over a wide 20–35-GHz frequency range with a programmable linearizer. A broadband design is achieved with a magnetically coupled resonator (MCR) technique that provides wideband impedance matching for the interstage and output-stage matching networks. Linearization is achieved with a topology consisting of inverter-based amplifier segments that provide programmable predistortion gains over the input signal regions. Fabricated in 28-nm CMOS, the driver delivers 2.5-Vpp swing to an external MZM. Operating the majority of the circuitry at 0.9 V, except for the 1.6-V output stage, allows for a power consumption of only 180 mW. The proposed programmable linearizer is able to compensate the amplitude-to-amplitude modulation (AM–AM) compression of the amplifier stages and the external MZM, extending output power 1-dB compression point ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {OP}_{1~\text {dB}}$ </tex-math></inline-formula> ) of the whole radio-over-fiber (RoF) link by 3 dB and achieving 4.8-dBm third-order input intercept point (IIP3) at 25 GHz.