A Compact and Robust GaN HEMT-Enabled Switchable Bandpass Filter for Integrated RF Systems

In this article, a highly miniaturized GaN HEMT-enabled X-band switchable bandpass filter is proposed. The filter utilizes GaN-on-SiC monolithic microwave integrated circuit (MMIC) technology to achieve miniaturization while maintaining high performance and integration capabilities. The bandpass filter topology using a coupled line structure is proposed to achieve low insertion loss (IL) with high power handling capability. A HEMT-based switching unit enables tuning of the transmission zero (TZ) and switching between ON and OFF states via direct current (DC) bias adjustment. The proposed switchable filter has been fabricated and measured, and it exhibits a small die size (0.6mm×0.855mm), a 3-dB bandwidth of 2.75 GHz (FBW = 25%), a minimum in-band IL of 1.85 dB, and an input 1 dB compression point (IP1dB) of 34 dBm. In the OFF state, the filter achieves a suppression of 26 dB. The measurement results show good agreement with the simulations. This work highlights the potential for advanced integration and manufacturability in high-frequency components, contributing to the development of compact and efficient radio frequency (RF) front-end modules.