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DARPA Creates 0.85 THz Solid State Receiver 84

Posted by samzenpus
from the from-the-lab dept.
hypnosec writes "DARPA, under its THz Electronics program, has designed a solid state receiver capable of THz (terahertz) frequencies thus inching towards the possibilities of transistor-based electronics that will operate at THz frequencies. The newly designed solid state receiver demonstrates a gain at 0.85 THz. This particular milestone is a stepping stone for the next target of 1.03 THz. Because of this achievement a host of DoD electronics capabilities can now be realized. One such application where this can be of use is for a sensor that will operate through clouds under a DARPA program dubbed VISAR."
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DARPA Creates 0.85 THz Solid State Receiver

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  • by SuricouRaven (1897204) on Sunday August 05, 2012 @02:32PM (#40887667)
    Not just for airports any more. With technology like this, they can start minaturising the tech so every cop doing a stop-and-search can inspect the suspect. For, ah, weapons. Of course.
    • by Lord Lode (1290856) on Sunday August 05, 2012 @02:57PM (#40887899)

      I also have a THz wave receiver. It's called "eyes".
      I also have this device capable of producing THz waves. It's a lamp.

    • by rrohbeck (944847)

      Yes! When can I buy those X-ray glasses that were advertised all over the place in the SciFi pulps?
      I never ordered one because I knew enough about science that it must be a scam, but now we can finally do it!

      • by Skapare (16644)

        Instead of buying X-ray glasses back in those days, I made my own. I got some plastic with a ribbed surface on one side, and placed two sheets with flat sides back to back. I cut them to fit some empty glasses frames. I had a few of my friends actually fooled that the double-imaging effect seen through them were parts of people's bones inside.

        • Wait, what? There was a real optical effect going on? I always thought they were just wacky designs with holes in them so you can see the other people at the halloween party...

  • by Anonymous Coward

    It's "gain at 0.85 THz", not "of".

    • Re:typo (Score:5, Funny)

      by Skapare (16644) on Sunday August 05, 2012 @02:46PM (#40887805) Homepage

      This is Slashdot, not Wikipedia.

    • Re:typo (Score:5, Informative)

      by jkflying (2190798) on Sunday August 05, 2012 @03:36PM (#40888223)

      Incorrect. Gain is unitless (Vout/Vin), and decreases pretty much proportionally to the inverse of the frequency on amplifiers, so chip makes use something called the Gain Bandwidth Product (GBP) instead of the 'pure' gain, because it is a much more useful number for specifying actual transistor/amplifier performance in real live working conditions. And the unit of the GBP, is, you guessed it! Hz. Thus, a transistor with a GBP of 0.85THz will have a gain of 1 at 0.85THz, a gain of 2 at 0.425THz etc. When I see a gain with units in Hz I subconsciously think 'GBP' and don't even miss a beat...
      See http://en.wikipedia.org/wiki/Gain%E2%80%93bandwidth_product [wikipedia.org] if my explanation doesn't make sense.

      • by MattskEE (925706)

        You're incorrect sir. The Slashdot summary misquotes the linked DARPA press release which clearly states "gain at 0.85THz".

        Gain-bandwidth product is mostly used for opamps because a given opamp could be put into an amplifier circuit with negative feedback which is either low gain and high bandwidth, or high gain and low bandwidth, and each circuit would have the same gain bandwidth product. For microwave/mm-wave amplifiers where 10dB of gain might be a luxury and most circuits don't make use of negative f

        • by jkflying (2190798)

          You don't need negative feedback for there to be GBP. GBP is pretty much just another way of measuring slew rate given a fixed amplitude.

          But still, the DARPA press release says "first solid state receiver to demonstrate gain at 0.85 terahertz", so each the entire circuit may just have a gain of 1.0001 for all we know... They might have just been aiming for 0.9THz but got a gain of 0.8, so they lowered the frequency until the transistor slew rate was able to keep up with the signal. And a 10-stage LNA means

  • by StandardCell (589682) on Sunday August 05, 2012 @02:42PM (#40887765)
    Article summary is incorrect.

    Sorry, EE major and I get annoyed reading this kind of thing...
    • by jkflying (2190798)

      What they actually should have said was a Gain Bandwidth Product of 0.85THz, but I'm guessing somewhere along the line a journo said something like "Hey my EE friend, what does GBP mean? I've never heard of it, is there anything simpler?" To which the EE friend replies, "It's basically just the gain."

      • by MattskEE (925706)

        Nope, DARPA press release clearly states "gain at 0.85THz". The purpose of this program is to push ahead the maximum frequency to enable terahertz radar, so they're shooting for frequency more than GBP.

        Anyway, GBP's of over 1THz have already been achieved in the fiber optic communication arena but at frequencies up to ~50GHz, not 850GHz.

        • by Rich0 (548339)

          At that frequency what would be the range of such a radar, except in more exotic conditions like transmitters at very high elevation or in deserts? I would think that atmospheric absorption would be a big problem.

          Maybe for air-to-air radar it might be practical - once the transmitter is at altitude the absorption of moisture would be less of an issue.

          • by MattskEE (925706)

            Range is a problem with THz partly because of the atmospheric loss but also in large part because the achievable transmit powers are so low. The benefit of THz is that it can penetrate things like dust, good for radar imaging in the desert, and it can also penetrate clothing, good for imaging you in the airport ;)

            What DARPA is building now is not going to be a field-ready unit, it will be a demonstration piece that pushes the state of the art forward to inform future work in the area.

  • All for war (Score:1, Insightful)

    by roman_mir (125474)

    Here is what they want this for:

    This revolutionary advance would give U.S. warfighters an advantage in an especially challenging portion of the RF spectrum

    As per usual, it's all for war, it's all that government is interested in.

    • Re: (Score:2, Insightful)

      by cavreader (1903280)

      Even the hint that a certain technology may have military applications is the surest way of getting large amounts of money to continue the research. Plus there is another world war on the horizon that will make WW2 look like a pillow fight. It's unavoidable to pretend otherwise. All those shouting "can't we all just along" will be the first killed. Should be the ultimate reality show.

  • !THz (Score:1, Offtopic)

    by ddrueding80 (1091191)
    I can do morse code at 1Hz, also known as 0.000000000001THz. Look! THz frequencies. 0.85THz is fast, but just because you used THz as the unit of measurement doesn't mean you have accomplished THz speeds.
  • Slow progress. (Score:5, Informative)

    by Animats (122034) on Sunday August 05, 2012 @03:01PM (#40887929) Homepage

    Another terrible article summary.

    In 2010, a solid-state device at 0.67THz was achieved. [irconnect.com] In 2012, that effort is up to 0.85 THz. Progress is slow, but continuing.

    Diode-type CMOS imagers for terahertz radiation [laserfocusworld.com] have been built. Those convert terahertz radiation into DC, which can then be amplified by standard techniques. But diodes don't have gain. That's why the original article emphasizes that this new device has gain.

    There are terahertz lasers, waveguides [sandia.gov], antennas, and other components that work up there. The situation is much like radar during WWII; there were a few components that could do specific things at radar frequencies (then 60MHz to 1.2GHz), but general electronics wasn't there yet. Most of the electronics in radars of that period ran at far lower speeds. They still worked.

  • It may have demonstrated 0.1dB of gain at 850GHz (seriously, let's not label it THz unless it actually makes THz), but unless it is linear, it is pretty useless for digital communications.

  • by MattskEE (925706) on Sunday August 05, 2012 @04:24PM (#40888579)

    The summary and linked press releases are light on details so here is what I gleaned from the photograph of the chip based on some experience in the area of microwave/mm-wave device and circuit work. There will probably be much more technical information in upcoming papers in the research literature.

    Based on the photo of the chip on the linked DARPA page [darpa.mil] this is not a receiver, but a low-noise amplifier (LNA) which would be used as the front-end for an imaging sensor or communications/radar receiver. It would be straightforward to turn this into an imaging detector at this point by adding a detector after the LNA though I don't think this has one. For a synthetic aperture radar more circuits will be required, especially a mixer to downconvert the frequency.

    The slashdot summary misquotes the article saying that the circuit has "gain of 0.85 THz" but should say "gain at 0.85 THz". The LNA appears to have 10 amplifications stages which is very large for a LNA, which suggests that the gain per stage is still quite low at 0.85THz. This is to be expected as the best per-transistor gain cutoff frequencies are not too far 1THz that I'm aware of. The circuit also appears to be built in coplanar waveguide (a metallized signal strip in the middle surrounded by two ground strips) which is easy to fabricate and good for a research environment but it has a higher loss than microstrip (a signal line above a ground plane).

    Anyway that's my 2 cents.

  • by Anonymous Coward

    Just like me, I have mega-bucks. 0.000002 million bucks in my pocket right now! If I put it in the bank, with interest it will have gain.

  • So this thing can receive signals at (just less than) a TeraHz... But is somebody transmitting on that frequency?

    Obviously the higher the frequency the more bandwidth is available but what about the characteristics of the atmosphere ? Is this for long distance communication? wouldn't clouds etc screw it up?

  • When a government agency funds something that works, the headline is always, "NASA builds this..." or "DARPA builds that..."

    But when a government agency funds something that doesn't work, the headline instead is, "Lockheed mess up this..." or "Boeing messed up that..."

    Did DARPA "create" this as the headline says, or did they just fund somebody else to do the research, design and implementation?

    http://www.laserfocusworld.com/articles/2012/07/northrop-grumman-demos-850-ghz-integrated-receiver-circuit-aiming-a

  • Geordi La Forge's VISOR allowed him to see between 1 hz and 100,000 THz. Isn't it kinda interesting that they used a name so similar?

  • When I was doing war toys, not all that long ago, (ok, I guess it was. Where did the time go?) 40 Ghz was considered really, really high.

  • "VISAR seeks to develop and demonstrate a targeting sensor which operates through clouds as effectively as today’s infrared (IR) sensors operate in clear weather. This revolutionary advance would give U.S. warfighters an advantage in an especially challenging portion of the RF spectrum.”

    The wars of the future will not be fought on the battlefield or at sea. They will be fought in space, or possibly on top of terahertz waves.

  • it goes to 11.
    Yes, I joke there. I do find it fascinating how stuff keeps getting pushed to the limits, and then we say "bah, we can do better!"

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