Sensor Network For non-Ionizing Radiation
Sensor Network For non-Ionizing Radiation
(OP)
Hi guys,
I am building a sensor network to detect devices in the 800 MHz to 2.4 GHz band using the AD8361. Obviously we want to detect cell phones, bluetooth and wireless connections with our network and be able to see all the power density on the area. We designed an Archimedean spiral antenna and we attached it to the AD8361 using SMA connectors. After that we want to use a microcontroller to digitalize the DC output of the AD8361, then send that digital signal to a data acquisition card as the PCI-1200 and finally use LabView to present the result.
My problem is: I dont know what kind of microcontroller use because the speed of the signals that we are sensing.
The output of the sensor is between 0V and 3.6V, what do you think I should use, 8 bits or 10 bits converter.
Do you have any comments about all this? About the antenna or the connectors?
PS: So far I'm thinking to use the PIC12F675
PS2: We would like to triangulate the radiation emitter too and try to locate the emitter in an area. How difficult is that? I would appreciate comments about that too or any other thing.
Thanks
J
I am building a sensor network to detect devices in the 800 MHz to 2.4 GHz band using the AD8361. Obviously we want to detect cell phones, bluetooth and wireless connections with our network and be able to see all the power density on the area. We designed an Archimedean spiral antenna and we attached it to the AD8361 using SMA connectors. After that we want to use a microcontroller to digitalize the DC output of the AD8361, then send that digital signal to a data acquisition card as the PCI-1200 and finally use LabView to present the result.
My problem is: I dont know what kind of microcontroller use because the speed of the signals that we are sensing.
The output of the sensor is between 0V and 3.6V, what do you think I should use, 8 bits or 10 bits converter.
Do you have any comments about all this? About the antenna or the connectors?
PS: So far I'm thinking to use the PIC12F675
PS2: We would like to triangulate the radiation emitter too and try to locate the emitter in an area. How difficult is that? I would appreciate comments about that too or any other thing.
Thanks
J





RE: Sensor Network For non-Ionizing Radiation
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Sensor Network For non-Ionizing Radiation
For example, if one sensor is adjacent to an 'extra, unexpected' low power emitter, then it will detect a high power density (thanks to the 1/r^2 law). This data point will throw off your 'triangulation' algorithm.
Basically - by converting the RF envionment to one or more simple scaler power density measurements, you've thrown away 99.999999...% of the information. You shouldn't expect much in what remains.
If you've got only ONE source, then it should work after a fashion. It might be difficult to be sure that there is only ONE source.
RE: Sensor Network For non-Ionizing Radiation
I believe that this chip is more intended for direct connection within low power transmitters. You might want to confirm that it will detect anything when you account for a low power source PLUS all path losses.
RE: Sensor Network For non-Ionizing Radiation
macgyver: i only care about power densities so i dont need a high speed microcontroller. my real problem about that is that i dont want to lose information so i would have to use the appropriate microcontroller. this will be the first time i work with this devices so i have no idea which one to use. Can you give me a hint please? Thanks for your comments and help mc.
VE1BLL: This is a 3 stages project and now i can assume there is only one source in the measure area. I know we cant be sure there is only one but in this stage we will probe our device in an OATS (Open Area Test Site) and in that way we can be sure our test emitter will have more power than others unknown radiation sources. Do you think under this circumstances an easy triangulation algorithm would work?
Actually i was thinking on do the LAbView program the easiest as possible. Just comparing the power density of each sensor (we will use 4 devices to have an square area)
and giving the biggest power density of the measure as the location of the radiation source could work. OF course the error using that would be huge but it could be a good approximation if there is only one radiation source and a small test area.
I would like to hear your comments about all this and any other comment from more people.
Thanks for your help.
Regards,
J
RE: Sensor Network For non-Ionizing Radiation
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Sensor Network For non-Ionizing Radiation
Since I will work in the 2.4 GHz, I will be sensing Wireless Access Points (WAP) using the 802.11b and 802.11g standards. This devices use FHSS and DSSS modulation techniques. This frequency hops occur really fast and each one of them has information about the total power density of the whole signal.
Besides, there could be more devices (i.e cell phone) in the measure area. Without the triangulation option I would like to have the information of that power density too. So, the DC out put of the sensor can change really fast and with the wrong uC I could lose information.
Please correct me if i am wrong but that;s what i think could happen.
Regards,
J
RE: Sensor Network For non-Ionizing Radiation
If you mean the protocol itself includes the capability to hold the power density then you have no hope of using a PIC to do that... it just doesn't have the power to decode the stream (at least by itself).
If you're talking about more simple measurements timed between each frequency hop, then your measurement speed will be based upon the dwell time set up by the system parameters. A system might have a dwell time of 200ms, which is plenty of time for a PIC to make a measurement and do some processing.
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Sensor Network For non-Ionizing Radiation
Besides that, what do you think about the "triangulation" problem that i talked about in the 5th post. Do you think it is a good approximation use that kind of comparison?
PS: We are simulating the Archimedean spiral antenna using CST simulation software. When i get final results i would like to share them with you and hear your opinion about them, what do you think about that?
Thanks for all your comments,
Regards
J
RE: Sensor Network For non-Ionizing Radiation
RE: Sensor Network For non-Ionizing Radiation
I want to sense cell phones, bluetooth and wireless connections working on the 800 MHz to 2.4 GHz band. As far as i know, all this devices work with omnidirectional antennas so "isotropic" sources wont be a problem. What is the best solution (or the problems) trying to triangulate this kind of devices using my system? Because my solution so far is the trivial one hehehe...
Is there any standard to do that? I would like to find an algorithm to use it in LabView.
Thanks for all your comments an support. I appreciate it
J
RE: Sensor Network For non-Ionizing Radiation
The normal triangulation method is to get several relative bearings and then, well, triangulate. My favorite Direction Finding technology is 'Doppler DF'. You can Google Doppler DF to learn more.
Time of arrival method is how GPS works.
RE: Sensor Network For non-Ionizing Radiation
What is the end use of your product? I realize you want to sense cell phones, but then what do you do with the information?
Is this for commercial use?
kch