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[silk] Spray-on Antennas Make Their Mark (fwd)

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  • Eugene Leitl
    -- Eugen* Leitl leitl ______________________________________________________________ ICBMTO : N48 10 07 E011
    Message 1 of 1 , Aug 1, 2001
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      -- Eugen* Leitl <a href="http://www.lrz.de/~ui22204/">leitl</a>
      ICBMTO : N48 10'07'' E011 33'53'' http://www.lrz.de/~ui22204
      57F9CFD3: ED90 0433 EB74 E4A9 537F CFF5 86E7 629B 57F9 CFD3

      ---------- Forwarded message ----------
      Date: Wed, 1 Aug 2001 13:07:21 +0800
      From: Ramjee Swaminathan <ramjee@...>
      Reply-To: silk-list@...
      To: silk-list@...
      Subject: [silk] Spray-on Antennas Make Their Mark

      Reading this interesting news item with the currently available
      'printable' computing device technologies (like Rolltronics) and sub
      dollar radio_freq_id tags (like Motorola) - the future has almost arrived
      for sub dollar disposable tracking systems, I guess. But may be not, it
      has to wait for 'printable' or 'sprayable' power systems...

      Some times (not always), I find these kinds of research troubling, when I
      consider the 'invasion to privacy' angle... For example, what if the
      employer_provided_freebie_jackets have the tracking system invisibly
      'printed' on them, in future?

      Paranoidally yours:



      July 2001

      ┬ęSIGNAL Magazine 2001

      Spray-on Antennas Make Their Mark

      Experimental technologies offer elegant, inexpensive solutions.

      By Henry S. Kenyon

      Researchers are studying applications and materials for creating radio
      antennas that are sprayed onto a surface. Made from commercially available
      materials, these devices consist of a conductive substance sprayed over a
      template with a radio aerial pattern on it. The antennas can be applied
      directly to walls, windows or fabric shelters, allowing military
      commanders and relief workers to set up communications networks quickly.

      Transporting, establishing and maintaining radio systems for military and
      humanitarian operations is often a logistics balancing act because of
      weight and space considerations. The ability to use any convenient surface
      as a mount for an aerial provides planners with additional flexibility
      when deploying in areas that are devastated or lack infrastructure.

      The Defense Advanced Research Projects Agency (DARPA), Arlington,
      Virginia, is considering a number of possible applications and techniques
      for using spray-on antennas. According to Dr. Paul J. Kolodzy, program
      manager, DARPA Advanced Technology Office, the goal is to develop easily
      transportable antenna apertures that can be deployed rapidly. For example,
      a command post staff could set up its communications infrastructure by
      spraying antennas onto tents, walls or windows. This concept could also be
      used where there is a temporary need for a large antenna. Instead of
      diverting resources to transport and assemble a large structure,
      communications specialists may find it more efficient to spray a pattern
      onto a large piece of plastic to create a dish, he says.

      Kolodzy cautions that the technology is still in its early concept phase.
      DARPA is examining materials that can emit or receive radio waves and is
      studying the capabilities of those substances in a particular antenna
      design. Once these operational parameters have been determined,
      researchers will be able to decide where to direct work on potential
      applications, he explains.

      The technology for the antennas is not exotic, Glynda Benham, president of
      MegaWave Corporation, Boylston, Massachusetts, explains. MegaWave is
      conducting a phase-two small business innovation research study for DARPA
      on possible uses for sprayable antennas.

      According to Benham, the antenna material is available in the form of
      metal-based paints such as nickel or silver and carbon-graphite-based
      paints. To create an antenna, a template is placed on the desired surface,
      the paint is sprayed over it and a connector is attached.

      These paints are currently used for electromagnetic interference shielding
      in cases for electronic equipment such as laptop computers. Marshall
      Cross, vice president for research and development at MegaWave, notes that
      an antenna could be built into a laptop casing on the production line
      simply by using a template to separate a section of the paint. This would
      be less expensive than installing a piece of metal for an antenna, he

      One potential difficulty will be creating a paint that maintains its
      integrity on fabric surfaces such as tents. The antennas must be durable
      enough to withstand repeated folding and washing for long-term
      applications, Benham says.

      DARPA research also will determine what kind of power a sprayable antenna
      will be able to put out in a transmission mode. This is important because
      too much power can destroy the antenna material, Kolodzy says. However,
      the primary goal of the research is to develop passive receiving systems,
      he adds. Additional studies seek new ways to find optimal patterns for
      antenna templates and to create apertures easily.

      MegaWave also has experimented with wideband antenna designs with
      bandwidth ranges from 200 megahertz to 3 gigahertz. While efficiency
      remains a concern, the goal of the current research is to see where the
      engineering and design boundaries lie. Kolodzy notes that if the broadband
      studies are successful, the results can be applied directly to narrowband

      The paints currently used for the antenna material are opaque. DARPA is
      interested in possible applications for transparent paints. Transparent
      antennas would be unobtrusive and could be installed on vehicle
      windshields, Kolodzy says. He notes that the military would like very
      large apertures for their antennas, and a windshield is often the largest
      uninterrupted surface on a vehicle that is available for mounting such a

      However, MegaWave researchers determined that no commercially available
      aerosol spray products currently meet transmission requirements because
      high temperatures are required to make the paint transparent. While
      several companies make metal-oxide-based materials for use at room
      temperature, they do not possess the minimum conductivity capacity of 100
      to 500 ohms per square inch necessary for an antenna.

      The study did reveal how much conductivity is needed to make this class of
      antennas, Cross observes. "It's almost like negative research. We figured
      out that with today's state of the art, you couldn't do it," he says.

      DARPA and MegaWave are also cooperating on developing "invisible" antennas
      built into transparent surfaces such as glass or plastic. Unlike sprayable
      antennas, these devices consist of films embedded into or placed over a
      windshield or a window to create a receiver. This technology also utilizes
      existing materials.

      Cross notes that automobile windows are coated with a metal-oxide film.
      This material currently serves three functions: as a safety laminate to
      hold the glass together during an accident, as protection for the
      vehicle's interior and occupants from ultraviolet and infrared rays, and
      as a demister or defogger when a current passes through it. A fourth and
      new function would be as a wideband antenna, he adds.

      In much the same way spray-on antennas can be created by separating a
      small template from a larger painted area, a transparent antenna can be
      made by cutting out and isolating an area of window film, Cross explains.
      This type of device could receive a variety of signals such as amplitude
      modulation, frequency modulation, global positioning system, cellular
      telephone and personal communications systems transmissions. Megawave
      currently is working with Southwall Technologies Incorporated, Palo Alto,
      California, to develop this technology for automotive use, Benham says.

      MegaWave also developed a prototype aircraft window for the Federal
      Aviation Administration. While the program did not proceed beyond the
      concept stage, it did demonstrate possible aerospace applications for the
      technology, Cross observes.

      The concept was to place a metal-oxide film on commercial aircraft windows
      to provide protection from sunlight and to shield communications and
      navigation systems from electromagnetic radiation emitted by personal
      electronic devices. The windows also could be used to detect and locate
      individual personal devices affecting aircraft avionics. "It's more bang
      for the buck. One piece of film does three things," Cross contends.

      Kolodzy hopes that these antenna technologies will be employed in areas
      such as the automotive industry and disaster relief. He believes that
      continued research will reveal more uses and capabilities for these
      devices. "It's going to be fun. If this works out, you're only limited by
      your imagination," he says.

      Besides developing unobtrusive and sprayable antenna technologies, DARPA
      is focusing on combining multiple aerials into a single unit. As part of
      its phase-two SBIR program with the agency, MegaWave developed a broadband
      antenna that would allow multiple radios to transmit and receive signals.

      According to Cross, the goal of the research is to develop multifunction
      antennas for law enforcement vehicles. "The idea is that you wouldn't
      drive around in a vehicle with five or six antennas on it because that
      tips off who you are. We got a used Ford Taurus and developed the whip and
      invisible windshield antennas and demonstrated that you could put many
      very high frequency and ultrahigh frequency radios on a single antenna and
      communicate just as well as with many antennas," he says.

      The modified device functions as a broadband whip antenna operating over
      multiple octaves. It is a resistantly loaded antenna--the resistances are
      distributed along the aerial's length in a manner that allows for wideband
      use without compromising much of its gain, Cross notes.

      The company has recently redesigned the whip with genetic algorithm
      techniques to optimize it for certain frequency bands, Benham explains.
      Genetic algorithms generate and produce efficient functions, much like
      real genetic traits are passed along by the dominant genes. This creates
      an automated method for optimizing antenna configurations. "When you do
      this process with genetic algorithms, instead of getting a continuous
      loading process, you get a piecewise, continuous profile that is totally
      random. It's not something you would ever get if you sat for 100 years and
      optimized it by hand," she says. --HSK

      Additional information on MegaWave Corporation's military antenna programs
      is available on the World Wide Web at http://www.megawave.com


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