Locating earthquake trapped victims using ISM band FMCW RADAR - Page 1
Forum section: electronics / general

author: MrOmnos
author_rank: Frequent Contributor
timestamp: December 05, 2016, 03:19:12 pm
content: Few months ago I posted the following video from MIT Lincoln lab where drones were used to detect peoples cellphones in search and rescue scenarios.I was testing my FMCW RADAR and I was receiving pretty good signal even when my transmit antenna was disconnected. Operating frequency of my radar is 2-2.5GHz so usually when I am testing my radar I turn off all the ISM band stuff in my home including my WiFi router. When I processed the recorded data in Matlab I found that it was my neighbors wifi router and knowing the layout of his house I could tell where the router was placed in the the house.So I wondering if the same technique can be used to locate people trapped in buildings in a search and rescue scenario since most people keep their phone wifi on all the time when they are at home or office. ISM band RADARs are cheap to make and can be easily mounted on drones. Just a thought, your input will be appreciated.Edit:I forgot to mention the most important part. You can do a SAR sweep with radar using a drone and overlay that over the existing map and see where the signal is coming from.Here the RADAR is operating in active mode and transmitting and receiving at the same time. Radar is on the ground.So, we use the radar to listen we can locate the source.

author: Bud
author_rank: Super Contributor
timestamp: December 05, 2016, 03:57:20 pm
content: Do you rely on the RX antenna directionality to pinpoint the signal source?

author: MrOmnos
author_rank: Frequent Contributor
timestamp: December 05, 2016, 04:18:28 pm
content: Quote from: Bud on December 05, 2016, 03:57:20 pmNo, I forgot to mention the most important part. You can do a SAR sweep with radar using a drone and overlay that over the existing map and see where the signal is coming from.Here the RADAR is operating in active mode and transmitting and receiving at the same time. Radar is on the ground.So, we use the radar to listen we can locate the source.

author: Bud
author_rank: Super Contributor
timestamp: December 05, 2016, 06:10:35 pm
content: Does your radar output phase information?

author: LaserSteve
author_rank: Super Contributor
timestamp: December 05, 2016, 08:29:26 pm
content: I knew that question was coming... Are you the same Bud that did the 10 Ghz work ?Steve

author: Bud
author_rank: Super Contributor
timestamp: December 05, 2016, 10:29:40 pm
content: I wish i did. No i have not gotten there. But i just recently had some reading on SAR and radar imaging and studied some math, though on a different subject. So i'd be interested in participating in the thread and learn more.

author: MrOmnos
author_rank: Frequent Contributor
timestamp: December 06, 2016, 10:16:58 am
content: Quote from: Bud on December 05, 2016, 06:10:35 pmI don't think it does.

author: Bud
author_rank: Super Contributor
timestamp: December 06, 2016, 02:56:00 pm
content: Ok, yes i think if you do not transmit then there is no phase reference. So is it a single antenna device and you swing it in horizontal plane to take data , then process the collected data to produce a combined image?

author: MrOmnos
author_rank: Frequent Contributor
timestamp: December 06, 2016, 03:34:38 pm
content: Quote from: Bud on December 06, 2016, 02:56:00 pmYou tune the local oscillator to a certain frequency for example 2.40001GHz and then mix it with the received 2.4Ghz signal from the wifi devices which will be give us a down converted signal of 10khz. We can easily be sampled 10 kHz signal with a soundcard. And then you swing it in horizontal plane to take data , then process the collected data to produce a combined image.

author: MrOmnos
author_rank: Frequent Contributor
timestamp: December 06, 2016, 03:41:37 pm
content: Quote from: Bud on December 05, 2016, 06:10:35 pmI think phase information is somewhat involved in during the SAR imaging. I forgot to mention, when doing a stripmap SAR you can get the phase information from the reflected waves from different elements of the target. I don't know how a single antenna SAR is going to work.

author: Bud
author_rank: Super Contributor
timestamp: December 06, 2016, 06:31:53 pm
content: I guess a single antenna is going to work same way as your setup on the ground, but the drone will reposition it instead of the swing motor or whatever you used. Seems you got a fairly good composite image, so the concept should work. I am only not sure about cell phones wifi transmissions, i do not know how often they transmit for the radar to pick up the signal. Perhaps the drone can carry an access point to make the phones transmit, do not know.

author: Bud
author_rank: Super Contributor
timestamp: December 06, 2016, 09:19:40 pm
content: Did you use eigenvalue/SVD decomposition to process the data?

author: MrOmnos
author_rank: Frequent Contributor
timestamp: December 09, 2016, 11:39:55 am
content: Quote from: Bud on December 06, 2016, 06:31:53 pmHi, those images are not from my RADAR. That is what I am planing on achieving. Those images are from a similar RADAR that I am building.

author: LaserSteve
author_rank: Super Contributor
timestamp: December 09, 2016, 07:20:22 pm
content: Phase comes from two detectors on the antenna waveguide a quarter wavelength apart. Worth doing for mapping and motion detection applications. A bit hard to do with a single coax without a circulator.Steve