Tech Briefs Magazine - April 2024 - 38

New Phase Shifter to Reduce Antenna Signal Loss
The technology shows low signal losses and extremely low phase deviation over a wide bandwidth.
University of Birmingham, United Kingdom
R
esearchers at the University of Birmingham
have developed a new type of
high-performance " phase shifter " using a
liquid gallium alloy - which varies the
phase angle of microwave and millimeter-wave
radio signals - for use in advanced
phase array antenna systems.
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
The high-performance phase shifter uses a liquid
Gallium alloy. (Image: www.birmingham.ac.uk)
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, " said Birmingham's Dr. Yi
Wang. " 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 team aimed to overcome these
long-standing issues by designing a new
type of phase shifter that controls the
phase shift via a liquid-metal material
that runs in microfluidic channels. The
prototype-testing results, published in
IEEE Transactions on Microwave Theory
and Techniques, show that the new phase
shifter shows low signal losses that are almost
independent of phase angle.
In addition, while most conventional
phase shifters provide different phase deLight-Based
Tech to Navigate the Moon
Thin lithium niobate chips aim to overtake their silicon counterparts in light-based technologies.
RMIT University, Melbourne, and University of Adelaide, Australia
R
MIT University's Arnan Mitchell and
University of Adelaide's Dr. Andy
Boes led an international team to review
lithium niobate's capabilities and potential
applications in the journal Science.
The team is working to make navigation
systems that help rovers drive on the
Moon - where GPS is unable to work
- later this decade.
By detecting tiny changes in laser light,
the lithium-niobate chip can be used to
measure movement sans external signals,
Mitchell noted.
" This is not science fiction - this artificial
crystal is being used to develop a range
of exciting applications, " said Mitchell.
" And competition to harness the potential
of this versatile technology is heating up. "
" Our lithium niobate chip technology is
also flexible enough to be rapidly adapted
38
to almost any application that uses light, "
he added. " We are focused on navigation
now, but the same technology could also
be used for linking internet on the Moon
to the internet on Earth. "
Lithium niobate is an artificial crystal
first discovered in 1949.
" Lithium niobate has new uses in the
field of photonics - the science and
technology of light - because unlike other
materials it can generate and manipulate
electro-magnetic waves across the full
spectrum of light, from microwave to UV
frequencies, " Boes said. " Silicon was the
material of choice for electronic circuits,
but its limitations have become increasingly
apparent in photonics.
" Lithium niobate has come back into
vogue because of its superior capabilities,
and advances in manufacturing mean that
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it is now readily available as thin films on
semiconductor wafers. "
A layer of lithium niobate, about 1,000
times thinner than a human hair, is placed
on a semiconductor wafer, Boes said. " Photonic
circuits are printed into the lithium
niobate layer, which are tailored according
to the chip's intended use. A fingernail-sized
chip may contain hundreds of
different circuits, " he said.
The team is working with Australia-based
Advanced Navigation to create optical gyroscopes,
in which laser light is launched in
both clockwise and counter-clockwise directions
in a coil of fiber, Mitchell noted.
" As the coil is moved, the fiber is slightly
shorter in one direction than the other,
according to Albert Einstein's theory of
relativity, " he said. " Our photonic chips
are sensitive enough to measure this tiny
Tech Briefs, April 2024
lay at different frequencies, 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.
A patent application has been filed to
cover the microfluidic channel wave-guiding
device, and the research team is now
seeking to license the novel technology
for development and commercialization
and is doing further research to expand
this protection.
" 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. "
For
more information, contact Ruth
Ashton at r.c.ashton@bham.ac.uk.

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Tech Briefs Magazine - April 2024

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