A Digitally Reconfigurable Shunt Capacitance in RF GaN Technology Based on Inter-Finger Capacitors

A. Chillico, S. Paul, B. Janke, S. Chevtchenko, W. Heinrich, P. Scheele, O. Bengtsson

Published in:

Proc. 20th European Microwave Integrated Circuits Conference (EuMIC 2025), Utrecht, Netherlands, Sep. 22-23, ISBN: 978-2-87487-082-8, pp. 202-205 (2025).

Abstract:

This paper presents a novel switchable capacitance cell containing two 4×125-µm Gallium Nitride (GaN) High-Electron-Mobility Transistors (HEMTs) with Metal-Insulator-Metal (MIM) capacitors embedded between the HEMTs’ fingers. The cell is capable of showing four different capacitances at its RF port depending on the HEMTs’ states, leading to the possibility of integrating it into reconfigurable power amplifiers (PAs). The cell shows good agreement with the expected capacitance values below 5 GHz, with Q-values above 50 up to 11 GHz when the HEMTs are OFF, decreasing to about 30 below 3 GHz when the HEMTs are ON. The reconfigurable cell is compared to a normal 4×125-µm HEMT and a 0.5 pF MIM capacitor, made in the same technology. The comparisons show that the cell’s Q-values are comparable to the one of the capacitor above 13 GHz when the HEMTs are OFF, while better than the HEMT at most frequencies. The different states of the cell are shown to be well modeled by a series RLC model.

Keywords:

Capacitors bank, GaN, HEMTs, power amplifiers, reconfigurable devices.

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