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From: | Marcus Müller |
Subject: | Re: [Discuss-gnuradio] Picking up RF cellular signals |
Date: | Tue, 15 Mar 2016 17:02:42 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 |
That is direction finding, not distance estimation based on signal
power. Two totally different approaches. You'll need at least two
antennas for direction estimation. Meny, you're an engineer, read up on the theory; it's actually fun to see these signal and geometric equations fall into place. In this case, Walter Kaminsky (who made that device from the video) holds a granted patent [1] on this specific device, and as a skimming of the abstract of that patent shows, direction finding is done by phase comparison. You'll find more details in the patent and if you look up direction finding in the literature/the internet. Direction finding through phase difference isn't such a complex concept mathematically, but non-trivial to implement in hardware (which is why Walter was granted a patent on a device that implements a rather well-known application); but if you have phase-coherent receivers, also not impossibly hard to build such a system with GNU Radio. It all boils down to writing a direction estimator. There's a *lot* of approaches and algorithms out there, but I'd recommend you start with something intuitive – maybe finding the relative phase of a received signal by estimating the phases of signals, and based on these phase relationship estimate the angle of the wavefront relative to your antenna array. Best regards, Marcus [1] http://www.google.de/patents/US6239747 On 03/15/2016 03:17 PM, Meny Sidar
wrote:
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