Hello,

We noticed you're browsing in private or incognito mode.

To continue reading this article, please exit incognito mode or log in.

Not an Insider? Subscribe now for unlimited access to online articles.

Christopher Mims

A View from Christopher Mims

Introducing the Electromagnetic Bazooka

A technique borrowed from acoustics could lead to a super-powerful amplifier of microwave radiation.

  • June 7, 2010

Non-nuclear electromagnetic pulses (EMPs), featured in movies like Goldeneye and The Matrix, are the stuff of electrical engineers’ nightmares. Imagine a conventional explosive that sends out a shockwave of electromagnetic radiation so powerful that it short circuits computers, stops cars dead in their tracks, and causes airplanes to drop out of the sky. Such devices might also have more prosaic uses: for example, two Texas congressman just proposed using EMPs to stop smugglers at the U.S.-Mexico border.

Previously, it was thought that creating an EMP of sufficient power to disable vehicles or infrastructure would require, at the least, a conventional chemical explosion. Work funded by the French Ministry of Defense, published earlier this year, describes an early prototype of an all-electric version of what the researchers describe as a potential “electromagnetic bazooka.”

The device borrows a technique invented in 2004 for audio signal processing by French physicist Mathias Fink, known as Time Reversal Signal Processing. The technique uses a Time Reversal Mirror to receive a short pulse of electromagnetic energy at an antenna and then shoot back toward the initial transmitter the same signal, but with its wave-form reversed in time. The technique is enabled by the use of an Arbitrary Waveform Generator, which can generate any waveform you like, including a backwards version of the waveform an antenna just received. It’s a bit like responding to a given signal by playing the same signal backward, although it happens in milliseconds.

When used on either audio signals or electromagnetic waves, a Time Reversal Mirror allows engineers to exploit what’s known as the “pulse compression property” of time reversal to create an amplified version of the signal at a point outside the reverberation chamber housing the transmitter and the time reversal mirror. Therefore, at some distance from the device, a significantly amplified version of the initial signal is generated.

Using this setup, the researchers discovered a linear relationship between the number of antennas (from one to eight) used in their time reversal mirror and the resulting amplitude of the microwave pulse they generated.

Further amplification of the signal before retransmission by the mirror, using a technique called “one-bit time reversal,” allowed the team to achieve 46 dB of amplification. Because decibels are represented on a logarithmic scale, that corresponds to amplification of the original signal by a factor of more than 10,000.

It’s clear that this work is early-stage because the paper did not make explicit the power requirements of the device or the destructive capacity of the resulting amplified electromagnetic signal, if any. However, as our infrastructure and our military becomes ever more dependent on microchips and electronics in general, any developments in the ease with which an EMP can be developed should be of considerable interest to military and security professionals, or even, if this device is as straightforward as it appears to be, enterprising attendees of next year’s Maker Faire.

Tech Obsessive?
Become an Insider to get the story behind the story — and before anyone else.

Subscribe today
More from Intelligent Machines

Artificial intelligence and robots are transforming how we work and live.

Want more award-winning journalism? Subscribe and become an Insider.
  • Insider Plus {! insider.prices.plus !}* Best Value

    {! insider.display.menuOptionsLabel !}

    Everything included in Insider Basic, plus the digital magazine, extensive archive, ad-free web experience, and discounts to partner offerings and MIT Technology Review events.

    See details+

    Print + Digital Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

    Technology Review PDF magazine archive, including articles, images, and covers dating back to 1899

    10% Discount to MIT Technology Review events and MIT Press

    Ad-free website experience

  • Insider Basic {! insider.prices.basic !}*

    {! insider.display.menuOptionsLabel !}

    Six issues of our award winning print magazine, unlimited online access plus The Download with the top tech stories delivered daily to your inbox.

    See details+

    Print Magazine (6 bi-monthly issues)

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

  • Insider Online Only {! insider.prices.online !}*

    {! insider.display.menuOptionsLabel !}

    Unlimited online access including articles and video, plus The Download with the top tech stories delivered daily to your inbox.

    See details+

    Unlimited online access including all articles, multimedia, and more

    The Download newsletter with top tech stories delivered daily to your inbox

/3
You've read of three free articles this month. for unlimited online access. You've read of three free articles this month. for unlimited online access. This is your last free article this month. for unlimited online access. You've read all your free articles this month. for unlimited online access. You've read of three free articles this month. for more, or for unlimited online access. for two more free articles, or for unlimited online access.