Thermopneumatic Liquid Metal Radiofrequency Switch Actuated by Low‐Boiling‐Point Fluid

Existing radiofrequency (RF) switches used in reconfigurable antennas often encounter performance issues such as high insertion loss, low isolation, and nonlinear effects of the switch. To address these issues, this article presents a liquid metal RF switch that utilizes a heated low‐boiling‐point fluid (LBPF) to drive the movement of a eutectic gallium‐indium alloy (EGaIn) plunger to turn the switch on/off. The operating principle of the switch is to use the pressure difference generated by the liquid–vapor phase change of the LBPF to make the EGaIn plunger to contact with, or disconnect from the copper electrodes of the switch. The performances of the RF switches actuated by different LBPFs are respectively investigated, and the results show that all RF switches have millisecond response times, and the contact resistances are as low as 0.14 mΩ. In addition, good RF performances are achieved, with an insertion loss of less than 3 dB and isolation of more than 17 dB in the frequency band from 0 to 2 GHz, and no nonlinear effects. This study also validates the performance of the proposed switch for frequency reconfiguration of a folded monopole antenna.