Improved-Q inductors using airbridges for GaN phase shifters

Abstract

This article proposes the use of inductors suspended in air to increase the self-resonance frequency and quality factor of inductors used in high-frequency lumped MMIC designs. This technique is compatible with MMIC processes having airbridges with no additional processing, which are quite common in III–V technologies. A measured example demonstrates lower dispersion, an increase in quality factor of 18% and a 4% increase in the self-resonance frequency of a 1 nH inductor in a GaN MMIC process with a 1 μm airbridge. As a further demonstration, the technique is applied in the design of a high-power 0°/45° switched phase shifter designed around 25 GHz. This phase shifter MMIC uses GaN HEMTs which have a peak ft of 27 GHz and offers wideband performance. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1455–1459, 2015