Subscribe free to our newsletters via your
. 24/7 Space News .


Subscribe free to our newsletters via your




















TECH SPACE
Ultra-thin, tunable, broadband microwave absorber may advance radar cloaking
by Staff Writers
Washington DC (SPX) Nov 17, 2015


For the first time, Stretching Transformation is applied to the unit cell pattern to expand the tunable bandwidth. With this technique, it is realizable to be thin and achieve broadband absorption simultaneously. Image courtesy Intelligent Electronics Institute, Huazhong University of Sci&Tec. For a larger version of this image please go here.

Microwave absorbers are a kind of material that can effectively absorb incident microwave energy to make objects invisible to radar; therefore they are commonly used in aircraft cloaking and warship stealth.

Recently, as radar detection devices have been improved to detect the near-meter microwave length regime, scientists are working on high-performance absorbers that can cloak objects in the equivalent ultra-high frequency regime (from 300 megahertz to two gigahertz).

However, conventional absorbers for the ultra-high regime are usually thick, heavy or have narrow absorption bandwidth, making them unsuitable for stealth missions.

To solve this problem, a team of researchers from Huazhong University of Science and Technology in China has developed an ultra-thin, tunable broadband microwave absorber for ultra-high frequency applications. This ultra-thin absorbing surface, called an active frequency-selective surface absorber, consists of arrays of patterned conductors loaded with two common types of circuit elements known as resistors and varactors.

The unit patterned cell absorbs microwaves and can also be actively controlled by stretching to expand the tunable bandwidth. In a paper published this week in the Journal of Applied Physics, from AIP Publishing, the researchers presented this work.

"Our proposed absorber was fabricated with a stretching transformation pattern, which is both thin and can absorb a wide range of frequencies for near-meter microwave application," said Wenhua Xu, the primary researcher in the team led by Jianjun Jiang, a professor of School of Optical and Electronic Information at the Huazhong University of Science and Technology, China.

"Its absorption range covers a broad band from 0.7 to 1.9 gigahertz below -10 decibel, and the total thickness of the absorber is only 7.8 millimeters, which is one of the thinnest microwave absorbers reported."

"Usually the thickness of conventional radar absorbers is a quarter the wavelength of the incident microwave. In the high frequency regime, take one gigahertz as an example, the thickness of the absorber would be around 7.5 centimeters, which is too thick and heavy to be used in aircrafts or warships. Our proposed absorber is almost ten times thinner than conventional ones," Xu said.

Other alternative absorbers, such as metamaterial absorbers made from a resonant metallic structure printed on a dielectric substrate, though significantly thinner than the wavelengths absorbed, have a narrow working bandwidth.

To develop a novel absorber that is both thin and with broadband performance, Jiang's team employed a type of thin, light periodic structure called a frequency-selective surface, which consists of an assembly of patterned conductors arranged in a two-dimensional array, usually backed by a thin dielectric, to reflect incident microwaves according to their frequency.

In the experiment, Jiang's team fabricated a broadband active frequency-selective surface with a stretching transformation pattern on a printed circuit board, and soldered the resistors and varactors between each of the two unit patterned cells. The fact that the surface could be stretched meant that the parameters of the unit patterned cell can be actively controlled by stretching.

By modeling the absorber using a transmission line, the researchers found that the varactor provides a variable capacitance at varying bias voltage, which produces the device's tunability, while the lumped resistor with constant resistance reliably produces strong absorption at the resonance frequency.

Besides the lumped impedances of the loaded elements, the researchers discovered that the parameters of the unit patterned cells contribute to the device's absorption performance as well.

"We applied various stretching transformation coefficients to the unit cell pattern to obtain the available parameters to expand the tunable bandwidth," Xu said. "Our results suggest that a cell pattern with a smaller stretching transformation coefficients ratio (i.e. width to length ratio of the unit cell) leads to higher resonance frequency absorption and produces a wider tunable bandwidth as well."

Xu noted that it is the first time that stretching transformation pattern is used in the active frequency-selective surface absorber to expand the bandwidth, which turns out to be an effective technique for producing broadband tunability.

"At frequencies below two gigahertz, conventional microwaves absorbers are limited in application by their thickness and narrow absorption bandwidth. Our proposed absorber has achieved broadband tunability and ultra-thin film simultaneously," Xu said.

"The total thickness of 7.8 millimeters is around one twenty-ninth wavelength of the central frequency of incident microwaves, and the ultra-thin absorber with broad bandwidth may be widely used in warship stealth, airplane cloaking and tunable, broadband antennae."

The researchers' next step is to study the polarization and the oblique incidence performance for the proposed active frequency-selective surface absorber.

The article "An ultra-thin broadband active frequency-selective surface absorber for ultrahigh-frequency applications" is authored by Wenhua Xu, Yun He, Peng Kong, Jialin Li, Haibing Xu, Ling Miao, Shaowei Bie and Jianjun Jiang. It will be published in the Journal of Applied Physics on November 10, 2015 (DOI: 10.1063/1.4934683).

.


Related Links
American Institute of Physics
Space Technology News - Applications and Research






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
TECH SPACE
New radar system announced by Israeli company
Ben Gurion International Airport, Israel (UPI) Nov 11, 2015
Israel Aerospace Industries has introduced a new radar system for early detection and tracking of long-range threats such as ballistic missiles. The system is called Terra, which combines ELTA System's ULTRA UHF band radar and the new ELM-2090S SPECTRA S-band very-long-range search and track radar. IAI said TERRA's enhanced performance is achieved through automatic handover and r ... read more


TECH SPACE
Gaia's sensors scan a lunar transit

SwRI scientists explain why moon rocks contain fewer volatiles than Earth's

All-female Russian crew starts Moon mission test

Russian moon mission would need 4 Angara-A5V launches

TECH SPACE
Upgrade Helps NASA Study Mineral Veins on Mars

Dust devils detected by seismometer could guide Mars mission

Amnesia Event Slows Down Opportunity Robotic Arm Work

Swiss Camera Leaves for Mars

TECH SPACE
Orion's European module ready for testing

General Dynamics demos SGSS Command and Control Infrastructure for NASA

Orion Service Module Stacking Assembly Secured For Flight

Global partnerships in orbit support economic growth on and off the Earth

TECH SPACE
China to launch Dark Matter Satellite in mid-December

China to better integrate satellite applications with Internet

China's satellite expo opens

New rocket readies for liftoff in 2016

TECH SPACE
Space station power short circuits, system repairs needed

Cygnus Starts Final Round of Processing for Station Cargo Delivery

US astronauts dodge ammonia on risky spacewalk

UK astronaut dreams of heavenly Christmas pudding

TECH SPACE
Recycled power plant equipment bolsters ULA in its energy efficiency

Purchase of building at Ellington a key step in Houston Spaceport development plans

More launches ahead for UH's Hawaii Space Flight Laboratory

LISA Pathfinder topped off for Vega launch that will test Relativity

TECH SPACE
Rocket Scientists to Launch Planet-Finding Telescope

5400mph winds discovered hurtling around planet outside solar system

New exoplanet in our neighborhood

Asteroid ripped apart to form star's glowing ring system

TECH SPACE
Computers tackle one of chemistry's greatest challenges

Conducting gels - from waste to wealth

Lockheed Martin introduces Digital Array Row Transceiver

Lasers could rapidly make materials hotter than the Sun




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News








The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.