Microfluidically Reconfigurable Rectangular Waveguide Filter Using Liquid Metal Posts

In this letter, the integration of microfluidically controlled liquid metal with WR42 rectangular waveguide to implement reconfigurable band-reject/band-pass filter is introduced. Here, microfluidic channels carrying liquid metal are used to realize off-centered adjustable partial/full-height circular posts at the dominant T E10 mode. First, a liquid metal post is partially inserted into the waveguide to create a tunable transmission zero over a 2.9 GHz rejection tuning range (18.20 GHz to 21.10 GHz). Next, the band-reject element (partial-height post) is used in conjunction with another microfluidic metal post to design a reconfigurable 1-pole band-pass filter with a transmission zero in the stop-band. The filter is configured for two states. The measured insertion loss of the filter at J0 is 2.3 dB and 2.8 dB while the return loss is better than 20 dB and 30 dB for State 1 and State 2 respectively.