Researchers led by Dr Yi Wang from Birmingham’s School of Engineering created the new type of high-performance phase shifter using a liquid Gallium alloy, which is said to vary the phase angle of microwave and millimetre-wave radio signals.
The phase shifter is a key enabling technology for advanced phased array antennas (PAA) used in mobile base stations, satellites and radar systems. PAA systems use multiple phase shifters to provide the controlled phase increments that steer the radiation beam (see below).
However current phase shifters typically use semiconductors and suffer from high loss of signal (so-called insertion losses) and relatively poor power handling capability.
In a statement, Dr Wang said: “An ideal phase shifter would provide a stable, and wide phase angle range with a minimal loss of signal over the operation bandwidth. 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 issues with a new type of phase shifter that controls the phase shift via a liquid-metal material that runs in microfluidic channels.
The results of prototype testing have been published in IEEE Transactions on Microwave Theory and Techniques. In their paper, the researchers show that the new phase shifter shows low signal losses that are almost independent of phase angle.
Furthermore, while most conventional phase shifters provide different phase delay at different frequencies, which limits their usable bandwidth and applicability, the new phase shifter is reported to have a phase compensation technique that provides extremely low phase deviation with frequency over a wide bandwidth.
A patent application has been filed that covers the microfluidic channel wave-guiding device, and the research team is looking to licence the technology for development and commercialisation.
Dr Wang said: “The new phase shifter does not need cleanroom facilities for fabrication, so is inexpensive to manufacture. The liquid-metal enabled phase shifting elements have a ‘passive’ nature, unlike the ‘active’ semiconductor-based counterparts, which potentially offers high power-handling capability.”
He continued: “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.”
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