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Cellphones Communications Science

Quiet Cellular Antenna Tech To Boost S. African SKA Bid 38

Posted by timothy
from the can-we-hear-them-now? dept.
slash-sa writes "Two South Africans have given their home country a boost with its Square Kilometre Array (SKA) bid by inventing cellular antenna technology which reduces 'noisy' emissions from cellular base stations in the area. They reduced emissions by using an antenna based on phased-array principles, providing omnidirectional coverage but also blocking the RF transmissions along a single direction (that would correspond with the bearing of the SKA core site). The antenna has been tested and performs extremely well. Trialling measurements have shown that the RF signal levels at the proposed SKA core site can be reduced significantly, while at the same time, much of the original GSM coverage can be retained."
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Quiet Cellular Antenna Tech To Boost S. African SKA Bid

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  • by rgbatduke (1231380) <rgb.phy@duke@edu> on Saturday October 29, 2011 @10:59AM (#37878860) Homepage
    Every cell phone tower in the US has access to extremely high precision time signals via GPS (and indeed, most of them function as secondary GPS locators by effectively forwarding that signal plus tower location data for phone "GPS" which isn't). Every cell phone tower is basically a big antenna. Every cell phone tower has excellent signal connectivity (usually fiber, sometimes microwave) to a communications network that can carry the signals they receive at any particular frequency, convolved with a universal time reference frequency synchronized by means of the aforementioned GPS, to a large processing station. Hence it is absolutely bone-simple to turn the entire network of existing cell phone towers into one great big radiotelescope.

    The cost of doing so is almost certainly going to be a tiny fraction of the cost of building an actual devoted function radiotelescope. I had a student estimate the cost per tower to be in the ballpark of $1000 US for a local computer and sundry electronics, probably less purchased in bulk. One could very likely get the tower owners to donate at least the access to the radio signals (basically costs them nothing), a place to site electronics (ditto), and with luck even a channel and some bandwidth to permit the upload of x-hours of recorded phase locked signal in off-peak bursts as part of their "public service" requirement.

    The additional benefit is that one ends up with a radiotelescope that spans a continent -- an aperture several thousand kilometers across, with hundreds of thousands to millions of towers contributing. The resolution would thus be orders of magnitude greater than any of these toys that they are trying to fund and the sensitivity (proportional to N^2) would be MANY orders of magnitude greater as well. In fact, one could probably build arrays that spanned continents and turn the entire surface area of the earth into one big radiofrequency "eye" that can be turned not just anywhere but everywhere 24x7 -- the towers basically record a high resolution hologram of the night sky and one can "look" in any direction you like within any single dataset by simply adjusting the phases of the recorded signals appropriately in the decoding. That is, one doesn't have to devote the towers to looking in some particular direction, one can look in all directions at once and choose what to actually look at in detail in the step where the signals are decoded and recombined with appropriate phase delays.

    This will never get funded, of course -- it isn't "big science" in any visible way. Or rather, perhaps it already has been funded, because it is one of the few ways I can think of that one could provide an ABM defense with a universal direction "eye" with sufficient resolution to locate an incoming warhead, and (by using the entire array as a phase-locked TRANSMISSION array) one might even be able to deliver a megawatt or so of power of microwave energy directly onto the missile itself and burn it out. Of course, if this is true then I guess I'll soon have somebody knocking on my door for publishing this on /., but so be it.

    rgb

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