I bought some cheap 10ghz and 24ghz dopper radar units off of amazon and started tinkering with them. You can absolutely pick up heartbeats and breathing just visually in the spectrogram.
Well if we follow the historic development arc, frequency-scanning waveguide arrays would come next. Nicely, very minimal modification required, and you can start cranking up the antenna gain. Mostly just a physical fabrication challenge, which is hobby-approachable.
Incredible work. Crazy that this could be done by a single person. Stick it on a rotating pedestal and you've got a planar radar detector. Add some tilt and then it's not much different than aircraft/weather radar I suppose.
The cost (in $LOCAL_CURRENCY, or $570 according to another comment) isn't great but I can only imagine how many hours this took.
Given a proper budget, the sky is the limit.
Anyone know how .mil aircraft would interpret being tracked by a 6 GHz radar build by a civilian(yes I am aware that his estimated max distance is 1200m, assume he increased that by a factor of 10 with larger antennas or something)?
> Anyone know how .mil aircraft would interpret being tracked by a 6 GHz radar build by a civilian(yes I am aware that his estimated max distance is 1200m, assume he increased that by a factor of 10 with larger antennas or something)?
Regulations for signal strength are ERP, so a more directional antenna could make it no longer legal to use the 6GHz band.
First and foremost, aircraft radars have receivers, which will also receive the transmitted pulse from the other radar. In fact, that is how radar jamming works - you deluge the other radar with power on the same band / wavelength, and it will fill the display with clutter.
With that said, radars have a bunch of characteristics that makes it somewhat easy to identify. Frequency, PRF (pulse-repetition frequency), waveform, etc.
The bands at which radars operates are regulated, and various agencies - military and otherwise - will pick up radar transmissions. These tiny DIY projects aren't a huge "threat" in that sense, but if you're active anywhere near a radar installation, and especially military ones, it could land you in hot water, real fast.
I'm not sure about Finland, but where I live, civilians for example are not allowed to fingerprint or build fingerprint databases of military radars. In fact, the military is the only ones allowed to do so.
The power-scaling makes these things go from DIY to non-DIY real quick.
Would be cool to see this guy build a phased-array (radar)
>Anyone know how .mil aircraft would interpret being tracked by a 6 GHz radar build by a civilian(yes I am aware that his estimated max distance is 1200m, assume he increased that by a factor of 10 with larger antennas or something)?
No specific knowledge, of course, but I'd imagine it wouldn't trigger a serious threat warning. Military TWRs are highly tuned systems dedicated to the threat environment they're expected to operate in.
The Finns strike again. Just the depth and number of different areas of expertise is insane to me. It seems he planned it all out, had it printed in China, and then 1/2 of the boards actually worked. That's like building a whole backend+frontend app and hoping it works after a month of coding on startup.
Regarding this "The suspiciously cheap $15 FPGA had equally suspiciously date and lot codes covered (white rectangles on the FPGA chip in the picture above). I have a development board of the same series chip with markings intact, so it definitely shouldn't look like this. It did end up working, but I wonder what the origin of these chips is."
I spoke with a GoPro operations guy once, and asked how you can get the chinese ripoffs at $40, that looked the same as their $400 "real" deal. He said that they literally get chips from scrapyards, like they get batches of memory chips that didn't pass the tests etc. They might work only in a very limited temperature range for example. Also many other components are picked and speced to work 6 months on avg not 6 years.. They know that most of those "gadget" products are bought and used for a weekend and then put in a cupboard anyway.
It would be fine for an R&D project like this but I would be very careful if I was going to make a commercial project (then you also have the politics side, probably fuelled by some paranoia - there are legislations coming up which prevents you from using chinese silicon components in products for certain markets)
>GoPro operations guy once, and asked how you can get the chinese ripoffs at $40, that looked the same as their $400 "real" deal. He said that they literally get chips from scrapyards
Chinese consumer electronics companies simply do not put huge margins on stuff. Here a great example, a $45 AlienTek DP100 100W USB-C micro lab power supply https://www.youtube.com/watch?v=Pd6LG7iP2GQ something like this would cost $500 with Digilent logo.
>speced to work 6 months on avg not 6 years
while original gopros suffer above average defect rates and cant record at 4K without baking itself to death/random shutdowns.
I've wanted to thank the author for a while for his past articles [1][2] which have been a wonderful source of information when working on my sonar systems [3]. This article again explains really well a complicated topic. Please, keep up the great work!
Beautiful piece of work. Henrik has a long history of interesting radar and other RF data-acquisition projects of the sort that you don't see publicly documented much, at least not at this level of quality.
Badass work. Rarely do you see such technical depth being demonstrated across the entire stack from RF to hardware to firmware to software. The article just gets better and better as you read on.
Why the ground planes are on layer 2 and 6 instead of 1 and 6 ?
Naively, as someone who doesn't have high frequency PCB design experience, I would have placed my grounds to form a shield and put my voltage plane on layer 3 or 4. I am sure that there is a good reason behind that choice but I don't see it.
Putting ground planes on top and bottom layers isn't usually done with high speed PCBs because components are there. There would need to be a cutout on the ground plane near every chip. High speed signals really need continuous ground plane and ICs, especially RF ICs, need short access to ground. Second layer is the best layer to minimize the distance from ICs to ground plane.
It is common to route high-speed signals on the top and bottom layers to avoid vias that cause impedance mismatches even when back drilled ($$$).
To maintain a specific characteristic impedance, you need a plane (GND) some distance from the traces which themselves have a specific width. Without a plane under/above the signals, you can't get a specific impedance value.
You can additionally fill the top and bottom layers, which marginally affects the impedance.
> Above is the final DDR3 routing on all the PCB layers. Layers 2 and 6 are ground, 5 is supply voltage, and others are reserved for signals. Two grounds are needed for correct impedances on the top, middle, and bottom traces of the PCB. With only one ground plane, the distance from the signal to ground would be too large on either the top or bottom layer.
Is the textual description in the article correct? To me the images make it look like signals are on 1 (red), 3 (orange) and 6 (blue), with ground on 2 (green) and 5 (pink) and supply voltage on 4 (teal). If you match some vias, you will find that 2 and 5 are definitely connected.
Obviously not the designer, but my guess is to lower capacitive loading on the matched high frequency signals (those with squiggles on top and flood underneath) and make modeling and IC mounting easier without flood. Note there's not flood near those either. I'm not quite sure on the ordering in the picture but it looks like 123/654? (edit ahh looks like the text was wrong and it is 123/456 with 2&4 Gnd). I'll note it looks like the internal "low speed" digital signals are squeezed between the gnd/pwr (edit: between gnd/gnd) planes, which is probably good since they're usually the biggest source of "noise" if you keep it away from other PCBs. You'd definitely want power/gnd planes immediately next to each other since bypass caps don't work at anything close to this frequency.
Speaking of radars... Did you know a useful radar is now just 34 US cents?[1]
And that chip? Not even designed for this application - it is a PIR sensor chip repurposed.
The core of the radar is just a single multi-Ghz transistor (in the middle of the left half of the PCB), and a super clever feedback circuit made out of fancy shapes of copper traces that probably took someone years to design and perfect.
AFE7225 is my goto for applications that require both DAC/ADC. ~$40 in single qty. Just limited to half the sample rate achieved here.
I personally wouldn't have bothered with Zynq here, so much easier to interface any FPGA with any COTS SBC over Ethernet. Or just use the $160 ZUBoard 1CG, perfect for quick prototyping.
Can someone explain why those differential pairs are routed with so many curves instead of straight paths? (E.g. see the photo under the “ADC and DAC rotting” section)
"The traces are length-matched with squiggly lines[...]. The trace matching requirement is ±10 ps according to the Zynq PCB design guide, which is approximately ±2mm in trace length. [...] There is also some delay difference inside the FPGA package which should be considered in the length matching."
This is a shortened excerpt from the article. It can be found below the image with six colorful images of PCB layers. I'm curious how the delays inside the FPGA package are known. Is there a table which pin adds how much delay to a signal or something like that?
Could this be adapted into a voxel system? Seems like it could be cheaper than LIDAR which are a huge cost for why the HW for self-driving systems are so expensive & work in far more environments that LIDARs struggle with. I suspect getting multiple directions simultaneously is hard?
Not without significantly complicating your antenna setup (and the data processing setup too). You guessed it, getting multiple directions simultaneously is hard. Note how the current system only detects distance and speed in 1 dimension.
Here's an analysis from someone smarter than me:
> To enable the new features, radar systems now use multiple input/multiple output (MIMO) antenna arrays for high-resolution mapping. Traditional radar systems usually contain two to three transmitting antennas and three to four receiving antennas, which lead to a beam providing limited short-range coverage and a narrow field of view unable to generate images. The limited angular resolution is insufficient to differentiate among vehicles, pedestrians, or objects that are close. The MIMO approach increases the underlying channels from only nine to anywhere between 128 and 2,000. Given radar’s significantly lower costs — even with all the enhanced technology — it’s easy to see how the two technologies will increasingly be on more equal footing.
Look at the forward looking automotive 4D (distance, speed, azimuth angle, elevation angle) radar systems. The new ones work at around 80GHz, and the entire thing comes in one integrated, tiny package, 16x16 phased array antenna already included with the MCs and FPGAs on the same board.
To go from those 4D radar maps to a voxel system requires a whole lot of software, of course.
The end goal seems to be to beat LIDAR on price and reliability (turns out moving mirrors don't like years of constant vibrations), while delivering enough resolution for self-driving.
> Cost was 330 USD for PCB manufacturing and assembly of two PCBs and additional 225 EUR (240 USD) for components from Digikey that I soldered myself. This is including 24% VAT and shipping costs.
jcims|1 year ago
I bought some cheap 10ghz and 24ghz dopper radar units off of amazon and started tinkering with them. You can absolutely pick up heartbeats and breathing just visually in the spectrogram.
Here's a few samples from that era:
10ghz pointed at ceiling fan:
https://www.youtube.com/watch?v=tIiFvByf1CQ
10ghz pointed straight up underneath a quarter that I flipped and allowed to land on the surface
https://www.youtube.com/watch?v=8riretP8ylE
10ghz pointed at a quarter spin on the surface
https://www.youtube.com/watch?v=5lnYvJoxRak
The comb filtering of the signal from the spinning surface is really cool.
10ghz module on amazon - https://www.amazon.com/HiLetgo-Microwave-Detector-Wireless-1...
spxneo|1 year ago
throwup238|1 year ago
It’s the last piece I needed for my suburban missile guidance system! This will be the last year the Joneses survive the annual block party.
Can you do phased array radars next? I need the extra precision. There’s a few neighbors who don’t clean up after their dogs…
gertrunde|1 year ago
https://www.crowdsupply.com/krakenrf/krakensdr
(Although they had to take the radar elements out of the firmware/software, most likely due to ITAR - ref link: https://forum.krakenrf.com/t/where-has-the-passive-radar-cod... )
spitfire|1 year ago
Tactical and Strategic Missile Guidance, Seventh Edition https://www.amazon.com/Tactical-Strategic-Missile-Guidance-S...
Tactical missile warheads https://www.amazon.com/Tactical-Warheads-Progress-Astronauti...
femto|1 year ago
"A DIY Cruise Missile: Watch me build one for under $5,000"
http://www.interestingprojects.com/cruisemissile/
mNovak|1 year ago
https://www.radartutorial.eu/06.antennas/Phased%20Array%20An...
Modified3019|1 year ago
Jon Kraft apparently is doing a series on that: https://www.youtube.com/@jonkraft
jcims|1 year ago
unknown|1 year ago
[deleted]
megous|1 year ago
rlt|1 year ago
auspiv|1 year ago
The cost (in $LOCAL_CURRENCY, or $570 according to another comment) isn't great but I can only imagine how many hours this took.
Given a proper budget, the sky is the limit.
Anyone know how .mil aircraft would interpret being tracked by a 6 GHz radar build by a civilian(yes I am aware that his estimated max distance is 1200m, assume he increased that by a factor of 10 with larger antennas or something)?
aidenn0|1 year ago
Regulations for signal strength are ERP, so a more directional antenna could make it no longer legal to use the 6GHz band.
TrackerFF|1 year ago
First and foremost, aircraft radars have receivers, which will also receive the transmitted pulse from the other radar. In fact, that is how radar jamming works - you deluge the other radar with power on the same band / wavelength, and it will fill the display with clutter.
With that said, radars have a bunch of characteristics that makes it somewhat easy to identify. Frequency, PRF (pulse-repetition frequency), waveform, etc.
The bands at which radars operates are regulated, and various agencies - military and otherwise - will pick up radar transmissions. These tiny DIY projects aren't a huge "threat" in that sense, but if you're active anywhere near a radar installation, and especially military ones, it could land you in hot water, real fast.
I'm not sure about Finland, but where I live, civilians for example are not allowed to fingerprint or build fingerprint databases of military radars. In fact, the military is the only ones allowed to do so.
The power-scaling makes these things go from DIY to non-DIY real quick.
Would be cool to see this guy build a phased-array (radar)
Source: Worked with radars
kijiki|1 year ago
No specific knowledge, of course, but I'd imagine it wouldn't trigger a serious threat warning. Military TWRs are highly tuned systems dedicated to the threat environment they're expected to operate in.
instagib|1 year ago
throwway120385|1 year ago
amanda99|1 year ago
Brusco_RF|1 year ago
l33tman|1 year ago
I spoke with a GoPro operations guy once, and asked how you can get the chinese ripoffs at $40, that looked the same as their $400 "real" deal. He said that they literally get chips from scrapyards, like they get batches of memory chips that didn't pass the tests etc. They might work only in a very limited temperature range for example. Also many other components are picked and speced to work 6 months on avg not 6 years.. They know that most of those "gadget" products are bought and used for a weekend and then put in a cupboard anyway.
It would be fine for an R&D project like this but I would be very careful if I was going to make a commercial project (then you also have the politics side, probably fuelled by some paranoia - there are legislations coming up which prevents you from using chinese silicon components in products for certain markets)
rasz|1 year ago
Chinese consumer electronics companies simply do not put huge margins on stuff. Here a great example, a $45 AlienTek DP100 100W USB-C micro lab power supply https://www.youtube.com/watch?v=Pd6LG7iP2GQ something like this would cost $500 with Digilent logo.
>speced to work 6 months on avg not 6 years
while original gopros suffer above average defect rates and cant record at 4K without baking itself to death/random shutdowns.
belzebalex|1 year ago
I've wanted to thank the author for a while for his past articles [1][2] which have been a wonderful source of information when working on my sonar systems [3]. This article again explains really well a complicated topic. Please, keep up the great work!
[1]: https://hforsten.com/radar-phase-measurements.html
[2]: https://hforsten.com/6-ghz-frequency-modulated-radar.html
[3]: https://twitter.com/alextoussss/status/1756371553460121766
CamperBob2|1 year ago
ein0p|1 year ago
nick__m|1 year ago
Naively, as someone who doesn't have high frequency PCB design experience, I would have placed my grounds to form a shield and put my voltage plane on layer 3 or 4. I am sure that there is a good reason behind that choice but I don't see it.
henrikf|1 year ago
bangaladore|1 year ago
To maintain a specific characteristic impedance, you need a plane (GND) some distance from the traces which themselves have a specific width. Without a plane under/above the signals, you can't get a specific impedance value.
You can additionally fill the top and bottom layers, which marginally affects the impedance.
_Microft|1 year ago
Is the textual description in the article correct? To me the images make it look like signals are on 1 (red), 3 (orange) and 6 (blue), with ground on 2 (green) and 5 (pink) and supply voltage on 4 (teal). If you match some vias, you will find that 2 and 5 are definitely connected.
kurthr|1 year ago
londons_explore|1 year ago
And that chip? Not even designed for this application - it is a PIR sensor chip repurposed.
The core of the radar is just a single multi-Ghz transistor (in the middle of the left half of the PCB), and a super clever feedback circuit made out of fancy shapes of copper traces that probably took someone years to design and perfect.
[1]: https://www.aliexpress.com/item/1005006240906322.html
unknown|1 year ago
[deleted]
mallets|1 year ago
I personally wouldn't have bothered with Zynq here, so much easier to interface any FPGA with any COTS SBC over Ethernet. Or just use the $160 ZUBoard 1CG, perfect for quick prototyping.
pythonguython|1 year ago
_Microft|1 year ago
This is a shortened excerpt from the article. It can be found below the image with six colorful images of PCB layers. I'm curious how the delays inside the FPGA package are known. Is there a table which pin adds how much delay to a signal or something like that?
ajb|1 year ago
cwillu|1 year ago
vlovich123|1 year ago
itishappy|1 year ago
Here's an analysis from someone smarter than me:
> To enable the new features, radar systems now use multiple input/multiple output (MIMO) antenna arrays for high-resolution mapping. Traditional radar systems usually contain two to three transmitting antennas and three to four receiving antennas, which lead to a beam providing limited short-range coverage and a narrow field of view unable to generate images. The limited angular resolution is insufficient to differentiate among vehicles, pedestrians, or objects that are close. The MIMO approach increases the underlying channels from only nine to anywhere between 128 and 2,000. Given radar’s significantly lower costs — even with all the enhanced technology — it’s easy to see how the two technologies will increasingly be on more equal footing.
https://www.oliverwyman.com/our-expertise/insights/2023/jul/...
pbmonster|1 year ago
To go from those 4D radar maps to a voxel system requires a whole lot of software, of course.
The end goal seems to be to beat LIDAR on price and reliability (turns out moving mirrors don't like years of constant vibrations), while delivering enough resolution for self-driving.
danielEM|1 year ago
KeplerBoy|1 year ago
Hats off to you!
brcmthrowaway|1 year ago
amirhirsch|1 year ago
unknown|1 year ago
[deleted]
AlwaysNewb23|1 year ago
henrikf|1 year ago
georgeburdell|1 year ago
davekeck|1 year ago
unknown|1 year ago
[deleted]