Wi-Fi

Metamaterial: the unnatural composite is transforming wireless technology


I get excited when I read about how scientists are able to create experimental conditions that do not occur normally in nature. Recently I was digesting an article on the PhysicsWorld website about how physicists have developed a method using a new class of materials called metamaterial to bring light to a complete stop. How is that even possible? Even with my limited expertise I started to comprehend the meaning of this, resulting in my imagination immediately going into total overdrive. Just think, we can now save the “Federation” because we have the technology to create devices just like the Klingon’s cloak. OK, I apologize, but the analogy was too good to pass up. Technology does actually exists that will cloak objects at microwave frequencies and it will just be a matter of time before it can be practically applied to the visible electro-magnetic (EM) spectrum.

Another example that is thankfully not based on my prolific imagination and related to the IT industry is how metamaterial-based devices are able to manipulate photons in the same manner that electrons are now controlled. This ability is a huge benefit in the world of fiber optic networks. To explain, if photons are used throughout the data transmission link, it avoids the need to convert the “zeros and ones” from one medium to another, thus eliminating bothersome timing issues typically associated with conversion buffers.

I suspect by now most of you are wondering what the heck this has to do with wireless radio technology and RF propagation. Technology using composites made from metamaterial is applicable across the entire EM spectrum and that includes every wireless device we all use on a daily basis. Before getting to specific examples, it is important to understand what a metamaterial actually is, so let’s start there.

Metamaterials defined

According to Wikipedia, metamaterial is a term first used by Rodger M. Walser of the University of Texas at Austin in 1999. He defined metamaterials as:

Macroscopic composites having a manmade, three-dimensional, periodic cellular architecture designed to produce an optimized combination, not available in nature, of two or more responses to specific excitation.

Alrighty then, let’s see if I can break that down a bit. Metamaterials are composite materials engineered to alter electro-magnetic wave behavior in very specific ways that up until now were non-existent in the natural world. This abnormal behavior is only possible because the structure of the composite is physically smaller than the actual wavelength of the EM signal that is propagating through the metamaterial composite. So what is this abnormal behavior that has researchers all excited?

Is Negative Index of Refraction that abnormal?

Scientists can now create a structure that exhibits a property called negative refractive index. This article by Duke University researchers explains negative refraction with reference to light, but once again this property applies to the entire EM spectrum. It is one of the best sources that I have found for explaining the difference between positive—naturally occurring—and negative refraction. As someone very interested in wave physics, I was sheepishly surprised to learn that EM waves only refracted in one direction and that negative refraction is understood to be abnormal.

Significance to RF propagation

Leaving elementary wave physics behind, let’s look at what this means with regards to RF propagation and why it is so significant. I once again take a back seat to the experts, letting Rayspan—one of the leading developers of metamaterial communications technology—explain what this all means:

What essential communications components and subsystems are enabled by metamaterials? Metamaterials technology brings three powerful enabling capabilities: (1) the ability to strongly manipulate the propagation of electromagnetic waves in the confines of small structures, (2) simultaneous support of multiple RF functions, and (3) the freedom to precisely determine a broad set of parameters which include operating frequency and bandwidth; positive, negative and zero phase offsets; constant phase propagation; and matching conditions and number and positioning of ports.

These capabilities make possible a broad range of metamaterial components and subsystems:

  • Physically small, but electrically large components such as compact antennas sized on the order of a signal's wavelength/10 while providing performance equal to or better than conventional antennas sized wavelength/2 - a five times size reduction.

  • Broadband matching circuits, phase-shifting components and transmission lines which preserve phase linearity over frequency ranges five to ten times greater than those provided by conventional counterparts.

  • Multi-band components whose frequencies of operation can be tailored to specific applications and are not limited to harmonic frequency multiples.

The last three points mentioned by Rayspan are especially significant. Each one has the potential to radically change our concept of RF propagation, almost to the point where there is a certain perceived intelligence involved with antennas. For example, Rayspan has developed metamaterial-based MIMO antenna arrays exhibiting performance characteristics equivalent to conventional MIMO antenna arrays, yet take up less space. The data sheet pertaining to the MIMO array is notably useful by furnishing actual azimuth and elevation radiation patterns.

Equipment developers are also starting to realize the potential of using components based on metamaterials. In fact Netgear introduced two new routers that use metamaterial antenna systems—WNR3500 and WNDR3300—at CES 2008. The routers and technology were reviewed by the very capable Tim Higgins at the SmallNetBuilder website.

What’s in store?

It is important to realize that this technology is not specific to 8o2.11 equipment. The use of metamaterial components will revolutionize all wireless and mobile technologies. In future posts, I would like to dig a little deeper into some of the specific device uses of metamaterial composites and other cutting edge antenna technology. One such example is “isolated mode" antenna technology which uses multiple feed points and a single antenna to achieve MIMO characteristics.

As a slight sidebar, I would sincerely appreciate hearing if topics like this are of interest. If not, what topics would be better suited and of interest to you the members?

About

Information is my field...Writing is my passion...Coupling the two is my mission.

19 comments
Michael Kassner
Michael Kassner

By the comments so far, I have come to realize that there are more pure science addicts around than I had imagined. I am very gladdened by that. With your permission I would like to continue broaching the pure science barrier every once and awhile. With that in mind, I am asking/begging for information as to what topics would be of interest. I would like to stay in the wireless realm if possible, but that is not a for sure thing.

TheGooch1
TheGooch1

Which are 2 things we really need to focus on until we solved the problem first brought to light in the 70's oil shortage in the US. Btw, this caught my attention "I was sheepishly surprised to learn that EM waves only refracted in one direction and that negative refraction is understood to be abnormal." because, if you remember from kinetics when solving parabolic formulas for time ( how long will it take the cannon ball to go a certain distance ) will sometimes ( often, in my experience ) give a negative and positive answer for time, but we alway discarded the negative answer as time could not possibly go backwards....right? But then why does the solution have 2 roots..positive and negative? If it a flaw in our mathematics? Or is it something else? In my Math Proof class, we'd just restrict the "universe" to positive integers before solving, but that is perhaps too artificial a restriction. What if time t is in the set of all real numbers, so therefore negative time is possible? Only time will tell ( pun intended ).

seanferd
seanferd

p=188 & p=189. Perhaps an effect of a negative index of refraction?

Michael Kassner
Michael Kassner

Does this topic have any interest? What other topics would you like to see discussed?

seanferd
seanferd

Plasma antennae are back in the research arena. I have no idea if they would make for a good technology in conventional wireless networking or telecommunications. Currently being developed for military applications. Various qualities, including stealth, are an effect of the antenna becoming a non-antenna once power is removed. It is also quite tunable, and relatively small. Ref: Scientific American, Feb. 2008, p22. Snippet at: http://www.sciam.com/article.cfm?id=aerial-stealth

JackOfAllTech
JackOfAllTech

There has never been an oil shortage. There was a gas shortage in the US caused by bad federal policy and greedy (US) oil companies, but there was, and is, plenty of oil.

jonsaint
jonsaint

Have you heard of using a device that adds capacitance to your home electricity demands in order to make more of your power consumption real power? Large buildings have used this since the 1950's with proveable results. There's a company selling the device now for home installation. http://www.power-save.com/faqs.html I'm going to install it this spring and see if it really makes a difference in my air-conditioning bill.

seanferd
seanferd

Feynman diagrams illustrate this beautifully. At the macroscopic level, the Arrow of Time is a fundamental mystery of the universe. Some physicists are now revisiting this conundrum. Your question is also somewhat like, "why are there not equal parts of matter and anti-matter in the universe?" Darn good questions, too.

Michael Kassner
Michael Kassner

That would be neat explanation to explore. But, the real reason is that I goofed up and after goofing up you have to wait a bit to un-goof it. I apologize for any confusion or inconvenience.

zetacon4
zetacon4

This is really interesting material. I want to follow up on your links posted in the article. Please continue posting articles of this nature and technical depth. You stimulated many questions with this fine article. I'm an editor, so excuse me for giving a tiny bit of assistance: you said: let?s look at what this means with regards to RF propagation and why it is so significant. There is no 's' on regard! A better way to use that word would be: let's look at what this means regarding RF propagation and ... Again, excellent article. Keep 'em coming.

jonsaint
jonsaint

I like pure science expositions to keep my mind working in my old age. But I love expositions of science advances that have near-term possibilites of exploitation in our lives.

JackOfAllTech
JackOfAllTech

I don't think the tech in TechRepublic applies only to Information Technology. I love this kind of stuff. I subscribe to Popular Science as well as Scientific American magazines. My cable company has about 8 different science channels from Nova to NASA to discovery. I watch them all.

seanferd
seanferd

I remember several years ago that researchers had been investigating this, I believe at microwave frequencies. At that time, it was stated that it was not thought that this could be accomplished at optical wavelengths, at least not anytime soon. I believe that this announcement qualifies as, "sooner than they thought". Interest-wise, I find this topic quite interesting. I am a big fan of science and engineering, pure as well as applied. As far as TR goes, I would assume that the subject matter would pertain somehow to IT. As to another topic: Perhaps Energy Conversion Devices, Ovonyx, or some other company, technology, or product involved with the research of Stan Ovshinsky, et al, such as amorphous solids in electronics (like RAM), may be of some interest if there is anything new coming out of this area. I'm not very current with this area, but I don't seem to find much information related to Ovonics mentioned any more. Perhaps that is because Stan retired, perhaps others are surpassing his work. Some technologies that Ovshinky's companies and partnerships were involved in are: Hydrogen economy, fuel cells, batteries, electronic switching and memory, and photovoltaics. This may be of interest if there is anything new coming out of these technologies, or possibly not. There is a broad range of technologies to investigate relating to Ovshinsky's work, so I thought it might be an interesting avenue to check out. In any event, I find most all of the high-tech research interesting, so keep it coming. Ah, another thought: RFID dust (Mitsuo Usami).

Michael Kassner
Michael Kassner

I must plead ignorance as I am not remotely familiar with plasma antennas. I hope that you have the patience to enlighten me.

seanferd
seanferd

It happens. Can't complain about two copies of something good, now can I?. :)

Michael Kassner
Michael Kassner

I appreciate any input regarding my use/abuse of the written language. It helps and I listen.

JCitizen
JCitizen

Take your time! I'm not in a hurry to gobble up more information than I can find time to absorb. Wished I was capable of it, but no. I greatly appreciate you and Michael's contributions.

seanferd
seanferd

because that is exactly what the antenna shown in SciAm was. Instead of a metal (a source of highly mobile electrons), the freed electrons of the plasma in a glass tube are used to emit or absorb radio waves. The power provided to excite the plasma is RF. The amount of power applied is what tunes the antenna. With the power off, the antenna is gone. Not only is it not emitting radio, but it will not reflect it either, like a metal antenna, hence the stealth application. I haven't done any further research on the subject, and the article is quite brief and very basic. What I don't know about this so far is: why is this antenna highly selective? Apparently, it will receive the freq it is tuned to, but not others, rendering reception noise free. For the military, this also provides a way to have a fairly un-jammable receiver, as it will only respond to the frequencies it is tuned to, and it won't reflect radar either if not tuned to something in the radar band. I have no idea when I am going to research this subject, or the many others that have caught my attention of late. I don't even know how much information there might be available on the current development of this technology, but there has got to be some older information around. Edit: Okay. A simple search for "plasma antenna" (I didn't even use the quotes) results in quite a few hits. One company is developing silicon solid state plasma antennae, and list wireless LAN among the applications: http://www.plasmaantennas.com/

Editor's Picks