A 148-GHz Radiator Using a Coupled Loop Oscillator With a Quad-Feed Antenna in 22-nm FD-SOI

Abstract

This article presents a 148-GHz coupled loop fundamental oscillator with a quad-feed octagonal slot antenna. The proposed loop configuration with a multi-feed antenna leads to each oscillator experiencing multiple injected signals. An analysis is performed to explain the dynamics of the coupled loop oscillator in the presence of multiple signal-injection paths. It is shown that the proposed oscillator configuration will only operate with - π/2 phase between the adjacent oscillators. This phase difference is necessary for the quad-feed antenna to combine and radiate the output power from the four single-ended oscillators in the loop. The output from each oscillator is ac coupled to the following oscillator stage using a phase compensating capacitor, whose value is selected to enhance the oscillation frequency of the coupled loop. The use of buffer stages is avoided in favor of a passive power feed network for extraction of the output power from each oscillator. The proposed oscillator is fabricated in a 22-nm FDSOI process and has a 0.5-mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> chip area. The measured peak effective isotropic radiated power (EIRP) of the oscillator is 9.7 dBm with a corresponding dc-EIRP efficiency of 34.3% when operating from a 0.8-V supply. To the authors' knowledge, this dc-EIRP efficiency is the highest among reported oscillators to date operating between 100 and 200 GHz.