5 ms·

> 60Ghz millimiter-wave radar > so it can go through walls 60 GHz RF doesn't really pass through anything, which is the entire reason that the frequency is us

> 60Ghz millimiter-wave radar > so it can go through walls 60 GHz RF doesn't really pass through anything, which is the entire reason that the frequency is used for radar. A radar needs powerful reflections to detect things. Penetration impedes its operation, and would be akin to a camera that is out of focus. I'm also unsure if the resolution of this chip is noteworthy.

mlyle 7y ago
Yup, the range claims are silly, too. Radar has an inverse fourth power with distance, so to go 10x as far by adding power, you need 10000x as much power, which is quite a challenge at 60GHz.
- GistNoesis 7y ago
  You are right that Radar follows an inverse 4th power with distance (inverse 2th power for the light to go to the reflected object then 2th power for the reflected wave to go back to your antenna). For 3$ https://fr.aliexpress.com/item/32786483344.html https://fr.aliexpress.com/item/32786483344.html a 6Ghz radar that goes 12meters using 30mA, so my range claims are not that silly. When there is no obstacle 6Ghz or 60Ghz doesn't matter.
  - mlyle 7y ago
    > When there is no obstacle 6Ghz or 60Ghz doesn't matter. Power amplifier efficiency for 6GHz and 60GHz is not the same-- not even close. > For 3$ https://fr.aliexpress.com/item/32786483344.html https://fr.aliexpress.com/item/32786483344.html a 6Ghz radar that goes 12meters using 30mA, so my range claims are not that silly. This is a deflection and ridiculous. We're talking about spotting e.g. gestures. It falls apart with distance because of both angular resolution and inverse-fourth power. I've been involved in the design of mmwave radars. If it was easy to spot and precisely track small objects at 10m, we'd be doing it...
    - GistNoesis 7y ago
      >If it was easy to spot and precisely track small objects at 10m, That's not the claim I'm making. I agree that this chip won't do the gesture recognition at 10m, but I'm quite convinced that it can pick up human movement signal if they try to do so. >I've been involved in the design of mmwave radars I don't have this level of expertise. But I'll be really surprised if we couldn't reach the same levels of amplification. Gaining 12 dB will double the range. We can extend the antenna array or use more expensive low noise amplifiers. For cars there are 30Ghz Doppler radar, and the distance can go at least 50m. From the referenced paper ( A Highly Integrated 60 GHz 6-Channel Transceiver With Antenna in Package for Smart Sensing and Short-Range Communications https://sci-hub.tw/https://doi.org/10.1109/JSSC.2016.2585621 https://sci-hub.tw/https://doi.org/10.1109/JSSC.2016.2585621 ) : "In this work a 60 GHz 4-channel receiver 2-channel transmitter packaged chip targeting high resolution sensing systems and capable of supporting large bandwidth communication channels is presented. The SiGe technology used offers a low 1/f noise which is essential to the functionality of the chip in frequency modulated continues wave systems (FMCW)and Doppler radar with a sensing range below 10 m." "While we have not explored this in-depth we would like to highlight the similarities to re-cent work exploiting FMCW RF technology to coarsely ‘image’ users through a wall [1]"
      - mlyle 7y ago
        Your second quote seems out of context and doesn't occur in the paper you cite. Your first quote says "sensing range below 10m". Yes, it is possible to make long range 60GHz systems-- largely through antenna gain and lenses. Yes, we could build an entirely different radar to track peoples' gross movement--- and could have 20 years ago, too-- but that has largely nothing to do with the original system or your original claim. If I wanted to image people at low resolution through a wall, 60GHz is about the last thing I'd pick. Drywall alone has an attenuation of about 3 dB/cm, and remember we have to cross the wall twice. You run out of loss budget really quick. Suggesting one can go 10x as far (10000x power alone) and through walls is... creative. If you want to track people through a wall, use UHF. It works pretty well and is pretty easy.
        7y ago
  - deleted 7y ago
    [deleted]
GistNoesis 7y ago
I am not familiar with 60Ghz. I agree that it has more problem going through obstacles. But usually when going higher frequency we can compensate by using more bandwidth. (Terahertz antennas use this to do crazy stuff.) The main reason it was chosen was to make it smaller to have everything integrated on a chip, and have an antenna array. Walls are typically static, which means they won't appear in the hardware amplified Doppler-shift signal (below 100Hz) which detect moving objects. (Radar works by amplifying the low frequency beating that occurs when adding two signal of high but close frequency 60GHz and 60Ghz+50Hz, low pass filtering then amplifying.) Typically the limits about power are dictated by how much attenuation (distance + obstacles) in dB *4 because inverse 4th power law, but as long as you are above the background noise you can amplify. Also here it is not trying to form a focused image, it is just gathering some signal to run some pattern detection algorithm. Even if there is a lot of noise we can integrate it with software fft over a long period of time, because we are trying to look for breathing movements (0.3Hz) which are even slower.
- arghwhat 7y ago
  > Walls are typically static, which means they won't appear in the hardware amplified Doppler-shift signal (below 100Hz) which detect moving objects. It will kill your SnR entirely, though. There will realistically be nothing to amplify.

mlyle 7y ago

Yup, the range claims are silly, too. Radar has an inverse fourth power with distance, so to go 10x as far by adding power, you need 10000x as much power, which is quite a challenge at 60GHz.

GistNoesis 7y ago
You are right that Radar follows an inverse 4th power with distance (inverse 2th power for the light to go to the reflected object then 2th power for the reflected wave to go back to your antenna). For 3$ https://fr.aliexpress.com/item/32786483344.html https://fr.aliexpress.com/item/32786483344.html a 6Ghz radar that goes 12meters using 30mA, so my range claims are not that silly. When there is no obstacle 6Ghz or 60Ghz doesn't matter.
- mlyle 7y ago
  > When there is no obstacle 6Ghz or 60Ghz doesn't matter. Power amplifier efficiency for 6GHz and 60GHz is not the same-- not even close. > For 3$ https://fr.aliexpress.com/item/32786483344.html https://fr.aliexpress.com/item/32786483344.html a 6Ghz radar that goes 12meters using 30mA, so my range claims are not that silly. This is a deflection and ridiculous. We're talking about spotting e.g. gestures. It falls apart with distance because of both angular resolution and inverse-fourth power. I've been involved in the design of mmwave radars. If it was easy to spot and precisely track small objects at 10m, we'd be doing it...
  - GistNoesis 7y ago
    >If it was easy to spot and precisely track small objects at 10m, That's not the claim I'm making. I agree that this chip won't do the gesture recognition at 10m, but I'm quite convinced that it can pick up human movement signal if they try to do so. >I've been involved in the design of mmwave radars I don't have this level of expertise. But I'll be really surprised if we couldn't reach the same levels of amplification. Gaining 12 dB will double the range. We can extend the antenna array or use more expensive low noise amplifiers. For cars there are 30Ghz Doppler radar, and the distance can go at least 50m. From the referenced paper ( A Highly Integrated 60 GHz 6-Channel Transceiver With Antenna in Package for Smart Sensing and Short-Range Communications https://sci-hub.tw/https://doi.org/10.1109/JSSC.2016.2585621 https://sci-hub.tw/https://doi.org/10.1109/JSSC.2016.2585621 ) : "In this work a 60 GHz 4-channel receiver 2-channel transmitter packaged chip targeting high resolution sensing systems and capable of supporting large bandwidth communication channels is presented. The SiGe technology used offers a low 1/f noise which is essential to the functionality of the chip in frequency modulated continues wave systems (FMCW)and Doppler radar with a sensing range below 10 m." "While we have not explored this in-depth we would like to highlight the similarities to re-cent work exploiting FMCW RF technology to coarsely ‘image’ users through a wall [1]"
    - mlyle 7y ago
      Your second quote seems out of context and doesn't occur in the paper you cite. Your first quote says "sensing range below 10m". Yes, it is possible to make long range 60GHz systems-- largely through antenna gain and lenses. Yes, we could build an entirely different radar to track peoples' gross movement--- and could have 20 years ago, too-- but that has largely nothing to do with the original system or your original claim. If I wanted to image people at low resolution through a wall, 60GHz is about the last thing I'd pick. Drywall alone has an attenuation of about 3 dB/cm, and remember we have to cross the wall twice. You run out of loss budget really quick. Suggesting one can go 10x as far (10000x power alone) and through walls is... creative. If you want to track people through a wall, use UHF. It works pretty well and is pretty easy.
      - 7y ago
- deleted 7y ago
  [deleted]

GistNoesis 7y ago

I am not familiar with 60Ghz. I agree that it has more problem going through obstacles. But usually when going higher frequency we can compensate by using more bandwidth. (Terahertz antennas use this to do crazy stuff.) The main reason it was chosen was to make it smaller to have everything integrated on a chip, and have an antenna array. Walls are typically static, which means they won't appear in the hardware amplified Doppler-shift signal (below 100Hz) which detect moving objects. (Radar works by amplifying the low frequency beating that occurs when adding two signal of high but close frequency 60GHz and 60Ghz+50Hz, low pass filtering then amplifying.) Typically the limits about power are dictated by how much attenuation (distance + obstacles) in dB *4 because inverse 4th power law, but as long as you are above the background noise you can amplify. Also here it is not trying to form a focused image, it is just gathering some signal to run some pattern detection algorithm. Even if there is a lot of noise we can integrate it with software fft over a long period of time, because we are trying to look for breathing movements (0.3Hz) which are even slower.

arghwhat 7y ago
> Walls are typically static, which means they won't appear in the hardware amplified Doppler-shift signal (below 100Hz) which detect moving objects. It will kill your SnR entirely, though. There will realistically be nothing to amplify.