Pulse Radar vs Stepped Frequency: which is really multi-frequency? | Ground Penetrating Radar (GPR)

[@concretegprllc1040]

Good stuff, thank you Dan. We've been eyeballing at least one upcoming concrete system that seems to use a CWSF model, and this is both timely and helpful.

[@Learngpr]

Concrete GPR LLC thanks so much for the comment. Glad you found it helpful. Hope all is well up north!

[@bdrogin]

Daniel, must be some ESP going on, I just started looking into this and wondered whether you put out a video on it - and you did 3 days ago! First, you are absolutely correct that the manufacturers are causing a lot of confusion. Second, as an EE, you're right, I'm going to be a little disturbed, but that's probably because we EE's know that a single pulse is a "broadband" signal and a continuous wave is a "narrow band" signal (try to parse that!). The literature I've found on continuous wave GPR has to do with detecting living and dead bodies in rubble after disasters and actual detection of heartbeat/heartrate as well as distance to body. There's step frequency, frequency modulated, and random (or pseudo-random) noise. What's most alien about these systems is you leave the transmitter in one place and accumulate data over, say, a two minute period, with a pretty wide cone radius. There's also impulse, which is not continuous. Some continuous wave (non-ground) radar systems detect Doppler shifts for targets moving toward (or away) from them, others (I think) use phase shifts, but the big difference appears to be frequency sampling rather than time sampling. Many manufacturers are either vague or confusing about how their systems actually work, so I only know about the researchers and the manufacturers who are more forthcoming. I really appreciate you attempting to parse this. It turned up because ASNT published a GPR puzzle where "frequency modulated continuous wave" was one of the answers, and I'd never heard of it!I'm guessing that you confuse continuous wave by drawing it as a succession of single impulses - my guess is it's actually a group of sinusoids at one frequency, followed by a group of sinusoids at a second frequency - but that's a guess, because the manufacturers aren't doing a great job of explaining what is actually going on. Will write to you privately about some stuff I've found and some answers from manufacturers I've learned. Thanks!!

[@Learngpr]

Thanks Barry. You took it to the next level! It is a massive issue, both the theory and the confusion by practitioners. I'll get back with you via email. Talk soon.

[@mujeebansari8680]

Hi sir very very thanks to you for your valuable information on multi frequency, I heard about gpr from German company called KS700 in which they are using F M C W frequency modulation channel or something else antenna or technology used by them so please provide more information about that types of gpr thanks

[@ZainalAbidin-xn9me]

Nice explanation dan. Tbh, I never see or even touch the GPR devices itself, but when I heard the term, I think the difference is that UWB antenna is transmitting all along the frequency at different time (ns), while the multi-pulse is at the same time. So, UWB is almost the same as SFCW. cmiiw

[@Learngpr]

Thanks for the comment. I think you bring up a great point about the timing of frequency.

[@weixiao900208]

Hello! Many thanks for the explanation! It is very clear and straightforward to beginners (me). Is it possible to give an introduction about how to manufacture a GPR. In addition, have you ever heard about any commercial MIMO GPR system?

[@Learngpr]

weixiao900208 thanks for the comment. I'm glad the video was helpful! I cannot do a video about how to manufacture a gpr since I never have...yet😊. I'll look into MIMO gpr. Keep watching!

[@weixiao900208]

Thank you so much! I am looking forward on your MIMO GPR video!

[@davitodil1364]

Darling Den, you get a few radarograms of different center frequencies for one profile ,? if so then it's understandable ..

[@Learngpr]

davit odil Hi! You should check out the video I did where I compare radargrams from a 250 and a 700. Thanks for the comment

[@Learngpr]

davit odil no. A single radargram with all frequencies. Or you can filter out frequencies.

[@slavrine]

Curious on how does CWSF distinguish what the frequency of the returned signal is. Does it do STA/LTA trigger (like in seismics) for each signal in the recording, does the Fourier transform to map out the frequency spectra and then finds the maximum for each signal?

[@Learngpr]

Stepan Lavrinenko thanks for the question. I believe it is a Fourier transform mapping frequencies/wavelengths. But don't quote me. You are better off asking an radar engineer.

[@saurabhsuman5697]

Hi Dan, As you said in earlier part of video in pulse Radar when we decrease the frequency the size of antenna increases as we will have a huge antenna while working with 100 Mhz frequency. How is this compensated in CWSF as i do have a GPR ranging from 30 Mhz to 3440 Mhz but the antenna spacing is same throughout?

[@jrglidden]

Interesting :D Multifrequency to me would (should) be multiple "bowtie" sets working together to send multiple signals at the same time. i really like the idea of them, being able to get good resolution of many depths.

[@Learngpr]

Joe Glidden agreed

[@streaminguide]

@Daniel What is the maximum depth of this gpr? In website it says 0.7 m. However, in website frequency is 0.2 ghz - 4 ghz. Normally the depth should be up to 6 m right? How come it become 0,7 m?

[@Learngpr]

Thanks for the question. The .2ghz to 4 is the full range. Its peak amplitudes are around 1 the to 3.5 ghz. Depth is always a function of time and they cut time around 20ns. I have seen deeper than 4 ft in quickly moving dielectric mediums. Hope this helps.

[@streaminguide]

LearnGPR I want to buy this product for experimental like burying some stuff in the ground and collect data. In short, your examples here to real life. That is why asked the depth. With raw data extracted, It is the same I mean it is cut?

[@oscarrrobayo4170]

Mala x3m is Pulse radar ? And dich witch 2150 gr is...?

[@Learngpr]

Yes. Though the mala might be a wide broadband. Certainly other mala are. The ditch witch is pulse

[@muhammadmuttaqin8198]

Hi sir, thanks for the explanation. By the way, what are the difference between CWSF / multiple frequencies with the Real-Time Sampling (RTS) technology?

[@Learngpr]

It all depends on what is meant by "multifrequency". That's kind of the point of the video...that word needs to be defined before it can be in the discussion.

[@oscarrrobayo4170]

please make a comparison between different brands...

[@gkpgeo]

I would need one cheap and best gpr of 50-100 mhz , could u please suggest. Also rental basis for a pre project evaluation survey for 10 days needed before buying

[@luizconte838]

quite similar to a seismic vibrator.

[@Learngpr]

Very

[@Hewhoyettoknowhimself]

Am I the only RF engineer that not feel disgraced 🤣