Wideband Switchable-Capacitor Loaded Differential Phase Shifter with Lattice Structures

Abstract

This paper presents a differential K/Ka-band switchable-capacitor loaded phase shifter with lattice structures using 28-nm CMOS technology. The lattice structure, which has a wideband characteristic, is loaded with switchable-capacitors and provides 22.5&#x00B0; phase shift. Seven of the lattice phase shifters are cascaded with a switched line 180&#x00B0; phase shifter, resulting in a full 360&#x00B0; phase shifter. The measured bandwidth for a root mean square (rms) phase error of &#x003C; 5&#x00B0; is from 22.5 to 33.5 GHz, where the rms amplitude error is &#x003C; 0.53 dB. The measured insertion loss is <tex>$\mathbf{11.6}\pm \mathbf{0.8}\mathbf{dB}$</tex> at 28 G Hz, and the input and output return losses are both&#x003E; 10 dB from 22.5 to 33.5 GHz. Over the 5G NR bands at 28 GHz (24.25 to 29.5 GHz), rms phase error is &#x003C; 2.4&#x00B0; and rms amplitude error is &#x003C; 0.49 dB. The fabricated phase shifter has a size of 0.45 mm2 excluding pads. The proposed K/Ka-band phase shifter based on lattice structures has a wide bandwidth while maintaining low rms phase and amplitude errors.