Liquid gallium alloy micro-fluidic mm-Wave phase shifter

The proposed shifter uses a half-mode substrate-integrated waveguide, with phase shifted in a via-pad-slot structure where a through via is attached to a pad surrounded by an annular slot.

Birmingham phase shifter with micro channels

“The phase shifter does not need clean room facilities for fabrication,” said lead researcher Dr Yi Wang, and “the liquid-metal enabled phase shifting elements have a passive nature, unlike active semiconductor-based counterparts, which potentially offers high power-handling capability”.

Equivalent to a shunt capacitance and inductance loaded on waveguide, liquid metal on the surface of the waveguide is used to alter phase.

“A self-compensation structure, based on multiple rows of via-pad-slots is proposed to achieve a low phase deviation with frequency”, according to a paper (see below) which describes the work.

Two proofs-of-concept have been built:

One with two via-pad-slot rows provides 0 to 41° shift with ±1° deviation over 9.5 – 12.5GHz. Average phase resolution is 1°, insertion loss 0.8±0.1dB and figure-of-merit of 45.6°/dB.
The second has three via-pad-slot rows to provide 0° to 180° shift with 1.68° resolution. Deviation is <±2° over 10 – 12.5GHz or <±5° over 9 – 13GHz. 1.1±0.1dB insertion loss was measured and the figure-of-merit was 163.6°/dB.

“Unlike many phase shifters, the loss of the proposed phase shifter does not increase with the phase shift,” according to the paper. “The measurements are in good agreement with circuit analysis and simulations.”

University of Birmingham Enterprise has applied for a patent.

‘Liquid metal-based tunable linear phase shifters with low insertion loss, high phase resolution, and low dispersion‘ describes the work in IEEE Transactions on Microwave Theory and Techniques.