Linearity Enhancement of GaN LNA MMIC Using RF-based Approach of Derivative Superposition

S. Haque^#, R. Doerner^*, S. Chevtchenko^*, M. Rudolph^*#

Published in:

Proc. 20th European Microwave Integrated Circuits Conference (EuMIC 2025), Utrecht, Netherlands, Sep. 22-23, ISBN: 978-2-87487-082-8, pp. 25-28 (2025).

Abstract:

This work presents a new methodology of implementing the derivative superposition (DS) technique based on third-order intermodulation current cancellation using harmonic-balance simulation. This approach is especially suitable for high-frequency applications due to the loading effect in transistors connected in parallel. To the best of the authors’ knowledge, this work demonstrates for the first time the implementation of the DS technique in GaN-based LNA MMIC. As a proof of concept, two single-stage 4.5–5.5 GHz LNA MMICs, with and without DS technique, are designed using FBH 250 nm GaN on SiC process, with a focus on improving linearity without additional power consumption. A two-tone measurement around 5 GHz shows a 6 dB output third-order intercept point (OIP3) improvement, from 38.7 dBm for a conventional LNA to 44.9 dBm for an LNA with DS. This leads to an improvement in the linearity figure of merit (LFOM = OIP3/P_dc) from 6.6 to 28.

Keywords:

Derivative superposition, GaN HEMT, intermodulation distortion, linearity, low-noise amplifier.

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