Phase shifter reduces signal loss in antenna systems

Researchers at the University of Birmingham, led by Dr Yi Wang, have developed a high-performance ‘phase shifter’ for use in advanced phase array antenna systems. Their results have been published in the journal IEEE Transactions on Microwave Theory and Techniques.

The phase shifter is a key enabling technology for advanced phased array antennas (PAA) which are widely used in mobile base stations, satellites and radar systems. These PAA systems use multiple phase shifters to provide the controlled phase increments that steer the radiation beam. However, current phase shifters typically use semiconductors and suffer from high loss of signal (insertion losses) and relatively poor power handling capability.

“An ideal phase shifter would provide a stable and wide phase angle range with a minimal loss of signal over the operation bandwidth,” Wang said. “However, conventional phase shifters suffer from signal losses which increase as the phase angle increases, and the phase varies with frequency. Taken together, these issues can cause signal degradation and impair performance. Rectifying this requires additional complicated circuitry and consumes more power, which adds to both the bulk and the running cost of the entire antenna.”

The research team set out to overcome these longstanding issues by designing a new type of phase shifter that uses a liquid gallium alloy, which runs in microfluidic channels and varies the phase angle of microwave and millimetre-wave radio signals. Their phase shifter was found to show low signal losses that are almost independent of phase angle. In addition, while most conventional phase shifters provide different phase delay at different frequencies (dispersion), which limits their usable bandwidth and applicability, the new phase shifter has a ‘phase compensation’ technique that provides extremely low phase deviation with frequency over a wide bandwidth.

“The new phase shifter does not need cleanroom facilities for fabrication, so is inexpensive to manufacture,” Wang said. “The liquid-metal enabled phase shifting elements have a ‘passive’ nature, unlike the ‘active’ semiconductor-based counterparts, which potentially offers high power-handling capability. Apart from the signature application in phased array antennas, the phase shifters may find a wide range of usages from communications and radars to instruments.”

University of Birmingham Enterprise has now filed a patent application covering the microfluidic channel wave-guiding device, and the research team is seeking to license the novel technology for development and commercialisation.

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