Gallium-based liquid metal substrate integrated waveguide switches

Research output: Contribution to journalArticlepeer-review


  • Shaker Alkaraki
  • James Kelly
  • Alejandro L. Borja
  • Raj Mittra
  • Yi Wang

Colleges, School and Institutes

External organisations

  • Queen Mary University
  • Universidad de Castilla La-Mancha
  • University of Central Florida


This letter presents a new approach for reconfiguring substrate integrated waveguide (SIW) devices. It involves allowing or prohibiting the wave propagation by using a removable wall which is built from a series of drill holes. When the wall is required, the holes are filled with gallium-based liquid metal (LM), thus forming vias. When the wall is no longer required, the holes are emptied of LM. The method has been applied to a single-pole single-throw (SPST) SIW switch as well as a single-pole double-throw (SPDT) switch. Both switches perform well over a wide frequency bandwidth, approaching one octave. The SPST switch performs well from 2.4 to 4.3 GHz. In the ON-state (i.e., wall removed), the insertion loss (IL) is ≤ 0.5 dB. In the OFF-state (i.e., wall inserted), the isolation is 30 dB. The SPDT switch operates effectively from 4.7 to 7.2 GHz. The IL, between two connected ports, is 0.7 dB. The isolation between unconnected ports is 40 dB. The proposed approach will be applicable within a wide range of different reconfigurable microwave devices.

Bibliographic note

Publisher Copyright: IEEE


Original languageEnglish
JournalIEEE Microwave and Wireless Components Letters
Early online date9 Dec 2020
Publication statusE-pub ahead of print - 9 Dec 2020


  • Eutectic gallium indium (EGaIN), liquid metal (LM), microwave switches, reconfigurable devices, RF/microwave switch, substrate integrated waveguide (SIW).