12 ms·
Homemade 6 GHz pulse compression radar
- l33tman 2y agoRegarding 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)
- rasz 2y ago>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 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.
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- londons_explore 2y agoSpeaking 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. [1]: https://www.aliexpress.com/item/1005006240906322.html https://www.aliexpress.com/item/1005006240906322.html
- danielEM 2y agoIs it legal? I mean, can you just make it and go to the street and play with it?
- throwup238 2y agoThis is great. 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…
- mNovak 2y agoWell 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. https://www.radartutorial.eu/06.antennas/Phased%20Array%20Antenna.en.html#fca https://www.radartutorial.eu/06.antennas/Phased%20Array%20An...
- megous 2y agoYou realize you can just go there and blow them up (ot shoot them up american style), right? Why the need for all the high tech?
- gertrunde 2y agoThere is this: https://www.crowdsupply.com/krakenrf/krakensdr 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-code-gone/98 https://forum.krakenrf.com/t/where-has-the-passive-radar-cod... )
- throwup238 2y agoThank you for the link! I totally forgot about kraken. I cloned their repo in November 2022, probably in anticipation of the ITAR hiccup. Hopefully the radar code is there.
- CobaltFire 2y agoI’d be interested in knowing if you’ve got that. I was going to buy one but the pull of the code put that on ice. I may pull the trigger if I can get the code!
- vlovich123 2y agoCould 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?
- itishappy 2y agoNot 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. https://www.oliverwyman.com/our-expertise/insights/2023/jul/lidar-radar-future-of-autonomous-driving-systems.html https://www.oliverwyman.com/our-expertise/insights/2023/jul/...
- georgeburdell 2y agoI just want to know how much this cost
- davekeck 2y ago> 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.
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- georgeburdell 2y agoPlus the test and validation equipment which are $$$
- henrikf 2y agoI actually didn't use any expensive test equipment, only oscilloscope and multimeter. Even design and simulation software was all open source. Expensive signal analyzer or spectrum analyzer would have been useful, but they aren't absolutely necessary. It's possible to use the radar itself for many tests and debugging. I have tried to limit the projects I do on my own to only the equipment that I have home and open source software.
- Yenrabbit 2y agoFantastic work! I enjoyed reading the previous posts as well, very interesting.
- rkagerer 2y agoI came to ask about that 24% VAT - ouch!
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- CamperBob2 2y agoBeautiful 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.
- nick__m 2y agoWhy 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.
- _Microft 2y ago> 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.
- nick__m 2y agothanks, layer 2 and 5 would fit the rest of the description and the reason would then be in the text : Two grounds are needed for correct impedances on the top, middle, and bottom traces of the PCB
- _Microft 2y agoHere are some resources on PCB layer stack-up by the way. While I'm an amateur, they didn't sound unreasonable. Chapter 10[0] has a list of links to different layer stack-ups for boards with 4 to 10 layers. [0] https://web.archive.org/web/20200124214936/http://www.hottconsultants.com/tips.html https://web.archive.org/web/20200124214936/http://www.hottco... Edit: removed wall of links
- henrikf 2y agoThat's a mistake in the text. You're correct that layers 2 and 5 are ground planes.
- auspiv 2y agoIncredible 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)?
- TrackerFF 2y agoThere are different ways 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
- throwway120385 2y agoWouldn't the FAA or FCC in the US have some jurisdiction over such a setup?
- maestroia 2y agoThe "6 GHz" band is an unlicensed frequency for very-low power (VLP) devices in the US. Specific bands are: "U–NII–5 (5.925–6.425 MHz) and U–NII–7 (6.525–6.875 MHz)". VLP is defined as those devices which "operate at up to −5 dBm/MHz power spectral density (PSD) and 14 dBm EIRP". https://www.federalregister.gov/documents/2024/01/08/2023-28006/unlicensed-use-of-the-6-ghz-band-and-expanding-flexible-use-in-mid-band-spectrum-between-37-and-24#:~:text=SUMMARY%3A,of%20the%206%20GHz%20band https://www.federalregister.gov/documents/2024/01/08/2023-28....
- AlwaysNewb23 2y agoThis is really impressive. Do you plan to use it for anything or another project?
- henrikf 2y agoI built it to see if I could. I didn't have any particular use case in mind.
- AnarchismIsCool 2y agoWould this be useful for another SAR setup?
- amirhirsch 2y agoDid you test this with arbitrary waveforms? Is it possible for you to accumulate complementary Golay Codes?
- jcims 2y agoI remember this article from the same site a while back - https://hforsten.com/heartbeat-detection-with-radar.html https://hforsten.com/heartbeat-detection-with-radar.html 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 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 https://www.youtube.com/watch?v=8riretP8ylE 10ghz pointed at a quarter spin on the surface https://www.youtube.com/watch?v=5lnYvJoxRak 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-10-525GHz/dp/B01N6AIF1L https://www.amazon.com/HiLetgo-Microwave-Detector-Wireless-1...
- spxneo 2y agointeresting does/can it work behind structures? is it safe to point this at yourself?
- lobocinza 2y agoI have a "human presense sensor" which is a 5GHz radar. It works behind structures, detection is weird sometimes but much better than a passive infrared sensor for this use case.
- KeplerBoy 2y agoyes, it's safe. It's not that different from regular WiFi or cellular signals. It's non ionizing (aka it doesn't have enough energy to instantly destroy cells unlike uv radiation) but it can heat up tissue, which is linked to cancer and worse (think microwave ovens).
- a_random_canuck 2y agoThere’s no risk of cancer from heating up tissue.
- pythonguython 2y agoCan 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)
- ajb 2y agoPath matching, as the other comments say, but also if you have a corner, at >Ghz frequencies it will emit RF.
- cwillu 2y agoMatching overall length with other traces, is my guess.
- _Microft 2y ago"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?
- henrikf 2y agoThe FPGA manufacturer has characterized all their package pin delays. It's possible to export a csv file with internal delays of the package for each pin from the FPGA design tool. With Xilinx Vivado it's just File -> Export I/O Ports.
- _Microft 2y agoDoes KiCad allow to take these delays for each pin into account automatically or do you need to do all that manually? Edit: it's using the pad property of "pad-to-die-length" if doing it manually, right?
- amanda99 2y agoThe 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.
- Brusco_RF 2y agoThat's pretty typical for hardware development. You software people have it too good!
- ein0p 2y agoBadass 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.
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- belzebalex 2y agoThis is incredible. 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 https://hforsten.com/radar-phase-measurements.html [2]: https://hforsten.com/6-ghz-frequency-modulated-radar.html https://hforsten.com/6-ghz-frequency-modulated-radar.html [3]: https://twitter.com/alextoussss/status/1756371553460121766 https://twitter.com/alextoussss/status/1756371553460121766
- KeplerBoy 2y agoHenrik Forsten is definitely the coolest radar guy on the internet I'm aware of. Hats off to you!
- brcmthrowaway 2y agoNah w2aew is better
- mallets 2y agoAFE7225 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.