Ormia ochracea is a small
parasitic fly best known for its strong sense of directional hearing. A female
fly tracks a male cricket by its chirps and then deposits her eggs on the
unfortunate host. The larvae subsequently eat the cricket.
doesn’t work out well for male crickets, such acute hearing in a tiny body has
inspired a Univ. of Wisconsin-Madison researcher as he studies new designs for
very small, powerful antennas.
Nader Behdad, an assistant professor of electrical and computer engineering, has
received a 2011 Faculty Early Career Development Award (CAREER) award and grant
from the National Science Foundation to pursue a novel approach to a challenge
that has thwarted electromagnetic researchers for more than a half century.
For a structure
like an antenna to effectively transmit or receive an electromagnetic wave at a
given frequency, the size must be comparable to the wavelength at that
frequency. Making the structure’s aperture size physically smaller than a
wavelength becomes a critical performance issue. These small antennas aren’t as
efficient and don’t work well beyond a narrow band of frequencies. Additionally,
many applications, such as satellite TV and radar systems, require antennas
that can distinguish signals from specific directions, and current small
antennas don’t have these precise directional capabilities.
small, directional antennas is one of those things we tell students can’t
happen,” Behdad says. “But the question is, what if it can be
to address the challenge through a new lens, one not often used in his field.
He is looking to nature for some design guidance, an approach known as
biomimetics or biomimicry.
He started by
exploring the human auditory system. Humans are equipped with a fairly good
sense of directional hearing, thanks to two ears separated by a head large
enough to attenuate sound. Humans also have a brain complex enough to calculate
the time difference between sound arriving in each ear and the intensity of the
sound to determine its origin. “We’re like a large antenna,” Behdad
gradually led to smaller creatures, such as mice and insects, and eventually,
Behdad came across the Ormia ochracea. “Some insects can hear in the same
manner we can. But their body size is small, so the time difference of the
sound arrival is significantly smaller,” he says.
insect’s “ears” are not even located on the head, but instead are
close together on its thorax or elsewhere, depending on the animal. Yet despite
the small time and intensity differences, some insects have directional hearing
capabilities surpassing those of humans. The parasitic fly, which appears to be
among the smallest with superb directional hearing, can detect the direction of
a chirping cricket with an accuracy of one to two degrees.
small antennas that actually work better than large antennas,” says Behdad,
who took this knowledge and began designing circuits that could mimic an
insect’s auditory system.
hasn’t been any work done to design antennas that mimic the hearing mechanism
of different insects,” he says. “We’ve designed a basic proof-of-concept
antenna and have some preliminary results. But at this point, we still need to
understand what the physics are.”
are for a type of antenna known as super resolving, which is capable of
distinguishing signals coming from different directions. If he can create very
small, efficient super-resolving antennas, the technology could result in
significantly more wireless bandwidth, better cell phone reception and other
applications in the consumer electronics industry, as well as new radar and
Behdad also is
interested in eventually using his CAREER research to explore small
super-directive antennas, a class of antennas that could capture a lot of power
coming from one direction. Though this type of antenna is still far from
reality, the result could be a tiny antenna with the capabilities of a giant
the CAREER award will support Behdad’s use of biomimicry beyond the lab. Behdad
will develop course modules to introduce undergraduate and graduate students to
biomimicry as a way of approaching a variety of engineering problems. He also
will partner with existing UW-Madison outreach programs to introduce the
concept to K-12 teachers as a way to engage younger students in science and