Re: [Discuss-gnuradio] gr-radar and FMCW radar imlementation for measuring range with high resolution

[Tilen Matkovič]

Hi,

thanks for quick reply!

I was aware of range resolution equation, apparently I didn't specify project enough and wasn't really paying attention while reading some articles :/.

Goal of my project would be to measure breathing/heartbeat rate of a human using FMCW radar in GNU radio. I just realized that I do not need to measure the distance of some object (human chest in my case), but only the phase variation, which would be much more precise for breathing monitoring than technique used in gr-radar, with some other limitations.

I believe that beam antennas would help me, so I will try to use them also, once I understand theory and get it working in implementation.

Article and webpage that helped me to understand such monitoring:

Smart Homes that Monitor Breathing and Heart Rate - http://witrack.csail.mit.edu/vitalradio/content/vitalradio-paper.pdf

http://hforsten.com/heartbeat-detection-with-radar.html

If such implementation for monitoring phase variation already exists in GNU radio, please point me in right direction :)

Regards,

Tilen

2018-02-08 19:02 GMT+01:00 Sebastian Müller <address@hidden>:

Hi Tilen,

Am 8. Februar 2018 um 16:31:37, Tilen Matkovič (address@hidden) schrieb:

Hello everyone,

I am working on a project where I am using radars to measure distance/range from one point to another (with relatively high range resolution - range of centimeters or even millimeters).

Generally I’m not sure if you will achieve this with the B210 hardware you mention later. Keep in mind the range resolution equation for radar:

dr >= c/(2*B)

For a range resolution of 1 cm you’ll need a signal bandwidth of 15 GHz [1], while the URSP has a maximum frequency coverage of up to 6 GHz, which means your center frequency plus half the bandwidth must be less equal 6 GHz. Common radars, for instance in automotive applications, work on a center frequency near 100 GHz, allowing much higher bandwidths!

I found the gr-radar (https://github.com/kit-cel/gr-radar/) module for GNU radio, which already has some implemented radar techniques, the most promising for me would be the FMCW radar. But the github repository was not updated in years, so I am asking you guys if some of you may know some alternatives for GNU radio (googling radar gnuradio was not so successful) or maybe anyone has already worked with gr-radar.

I’m not aware of any other projects, but I’ve used gr-radar myself. It definitely works in the real world, which you can see on Stefan’s Youtube channel [2].

Now what exactly is my problem - I managed to get the gr-radar - FMCW working on one USRP B210 (with TX/RX and RX2 using omnidirectional antennas). I was playing around with modifying some of the variables but I am still not getting useful range data (mostly it is constant, even if moving both of the antennas for a few meters or putting some obstacles in between). Modifying the samp_rate or sweep_freq, and others (samp_cw, samp_up, samp_down) has also not given me useful results.

The original setup for gr-radar consisted of two USRP N210, connected with a MIMO cable. It never ran on a B10, though there were some attempts, that seem to never have been further pursued [3].

Also, since you’re using omnidirectional antennas with FMCW, you’ll detect a lot of static objects in *all* azimuth angles, while gr-radar was designed for one target only IIRC. So assuming it theoretically could work on a B210 (please let us know!!), I would propose to use beam antennas and try to use the dual CW waveform, which only detects moving objects.

Let us know about any progress :)

Perhaps I am doing something wrong and not understanding the theoretical principles about radars/signal processing or maybe the FMCW flowgraph is not implemented correctly? I also have to mention here that author (on github) only tested the FMCW flowgraph in the simulation (which works ok), but not on the hardware.

Thanks for your help.

Regards,

Tilen

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[1] http://www.radartutorial.eu/01.basics/Range%20Resolution.en.html

[2] https://www.youtube.com/channel/UCv7cqqFkkiRFJIGkNEyMu3g

[3] https://github.com/kit-cel/gr-radar/issues/19

Regards,

Sebastian Müller

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PGP ID DC2AA3EE

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