Simplifying antenna design
through IC integration
Improved IC integration is making it easier to design flat-panel phased
array antennas, as Jeff Lane explains
A dvances in semiconductor
technology have enabled the
proliferation of phased array
antenna with active electronically
scanned antenna (AESA) in satcom
on-the-move and 5G communications.
Electrically steered phased array
antennas offer benefits such as
having a lower profile, less volume,
improved long-term reliability, faster
steering and multiple beams.
A key aspect of the phased
array antenna design is the spacing
of the antenna element and the
half-wavelength element spacing
needed for most arrays does create
particular challenges at higher
frequencies. Consequently, ICs at
higher frequencies are now more
integrated and packaging solutions
have become more advanced.
Semiconductor technology is
looking at more advanced silicon
ICs that combine digital controls,
memory, and RF transistors onto the
same IC. Gallium nitride (GaN) is also
significantly increasing the power
density of power amplifiers to offer a
smaller footprint.
Phased array technology
There is a major push toward low
profile arrays with less volume and
weight. Designs are moving from a
‘plank’ architecture to a flat-panel
approach, reducing the depth of
antennas and making them easier
to fit.
In planar array designs, the space
available for ICs on the back side of
the antenna is limited by the antenna
element spacing – e.g. the maximum
Author details:
Jeff Lane is
a Product
Marketing
Engineer, Analog
Devices
was offered as separate packaged
devices.
More advanced solutions could
have an integrated monolithic singlechannel
gallium arsenide (GaAs)
IC to achieve this functionality.
Included in most arrays before
the beamformer are a passive RF
combiner network, receiver/exciter
and signal processor.
The recent proliferation of
phased array antenna technology
has been aided by advancements
in semiconductor technology. The
advanced nodes in SiGe BiCMOS,
silicon-on-insulator (SOI), and bulk
CMOS have combined digital and
RF circuitry and can perform the
digital tasks in the array, as well as
control the RF signal path, to achieve
the desired phase and amplitude
adjustment.
It’s possible to achieve
multichannel beamforming ICs that
perform gain and phase adjustment
in a 4-channel configuration, as
well as up to 32 channels aimed at
mmWave designs.
In some lower power examples,
a silicon-based IC could be a
monolithic solution for all the
previous functions. In high power
applications, gallium nitride-based
power amplifiers significantly
increase the power density that
may be fitted into the unit cell of a
phased array antenna.
In airborne applications, there’s
a trend to flat-panel architectures
with the power added efficiency (PAE)
benefits of GaN technology. GaN has
also enabled large ground-based
radars to move from a dish antenna,
driven by a TWT, to phased arraybased
antenna technology, driven by
solid-state GaN ICs.
antenna element spacing to prevent
grating lobes for up to a 60° scan
angle is 0.54 λ. As you go higher
in frequency, the spacing between
the elements becomes quite small,
leaving little room for components
behind the antenna.
More integrated ICs help to
reduce the challenges in laying
out the antenna design with the
required spacing. With more
electronics packed into a reduced
footprint, antenna’s demand new
semiconductor and packaging
technology to make solutions viable.
The microwave and mmWave IC
components used as building blocks
for a phased array antenna are
shown in Figure 1.
In the beamforming section, the
attenuator adjusts the power level at
each antenna element so that the
sidelobes of the antenna pattern can
be reduced. The phase shifter adjusts
the phase of each antenna element to
steer the antenna’s main beam, and
a switch is used to toggle between
transmitter and receiver paths.
In the front-end IC section, a
power amplifier is used for the
transmit signal, a low noise amplifier
for the received signal and another
switch is used to toggle between
the transmitter and receiver. In past
implementations, each of these ICs
Figure 1: Typical RF
front end of a phased
array antenna
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