Liquid Metal-Enabled Waveguide Coupler With Continuously Tunable Power Division Ratio

A new concept to realize 3D waveguide couplers with continuously-tunable power division ratio (PDR) is proposed. It is based on a novel liquid metal (LM)-based tuning technique where the coupling between the input and output ports of the 3D coupler is continuously-tuned by reconfiguring the height of two LM posts using pneumatic actuation. For proof-of-concept validation purposes, an experimental monolithic prototype was built using stereolithography apparatus (SLA) 3D printing and a commercially available plating process and it was tested at Ku-band. It demonstrated the following unique RF performance characteristics: center frequency: 14.25 GHz, continuously-tunable PDR between -17 dB to +17 dB and operational bandwidth between 13.7-14.9 GHz (1.2 GHz). In this bandwidth, the input return loss was measured above 10 dB, the isolation above 10 dB and the overall loss below 1 dB.