A new water-based waveguide absorptive switch is developed and reported. The switch functions by controllably inserting water inside a conventional Ka-band waveguide. In particular, three Teflon-made circular cylinders with a diameter of 1.59-mm are placed inside a 50-mm-long waveguide section at an angle of 75 and can be filled with water by micropumps. The water-filled tubes offer a measured isolation of 18 and 28 dB at 26.5 and 40 GHz respectively. When water is removed the total insertion loss is measured at less than 0.5 dB across the whole band. This number includes the effects of (a) the 50-mm long waveguide section, (b) the holes for inserting the Teflon tubes, and (c) the tubes themselves. In addition, the measured switch return loss is greater than 18 dB at both states from 26.5 to 40 GHz. Water can be inserted and removed at a simulated speed of less than 50 ms. The proposed design requires approximately 40% less volume than conventional waveguide absorptive switches.


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micropumps, microswitches, microwave switches, waveguide components

Date of this Version

January 2008



Published in:

2008 IEEE MTT-S International Microwave Symposium Digest - MTT 2008 (2008) 185-8;



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