5 ms·

I discourage anyone wanting to understand the physics of beamforming antennae from reading this article. The author has a very poor grasp of the concepts.

akerl_ 12y ago
Can you elaborate? Without some kind of analysis of the mistakes in the article, we don't really have a way to judge if we should belief your statement about the author, nor can we improve our understanding. A more descriptive listing of some of the issues with the article, or links to better resources, would rock.
- madengr 12y ago
  Well to start, the antenna generates it's own noise since it is not 100% efficient; i.e. it has a real resistance in addition to it's radiation resistance. If you put a real antenna in a box made of perfect electrical conductor, it would still generate noise, so you really don't halve the noise by increasing the gain 3 dB, you double the signal. Here is a good tutorial on phased arrays. It's actually a lot easier to think of it when receiving a skewed wavefront, and the phase shifters (delay elements) compensating for the delay. http://www.radartutorial.eu/06.antennas/an14.en.html http://www.radartutorial.eu/06.antennas/an14.en.html
  - jerf 12y ago
    OK, while that seems like a valid tidbit if one has to implement this stuff, it doesn't seem like that's a helpful complication to introduce when trying to explain the basic concept.
- abstrakraft 12y ago
  Any time someone appeals to quantum physics to offer a handwaving explanation of something that classical physics covers just fine, watch out. Using path integrals to introduce interferometry is a waste of time, and in this case, just plain wrong. For a better source, I'd start with the wikipedia articles on beamforming, phased arrays, and interferometry (http://en.wikipedia.org/wiki/Beamforming http://en.wikipedia.org/wiki/Beamforming, http://en.wikipedia.org/wiki/Phased_array http://en.wikipedia.org/wiki/Phased_array, http://en.wikipedia.org/wiki/Interferometry http://en.wikipedia.org/wiki/Interferometry).
  - MarkSweep 12y ago
    Both the beamforming Wikipedia article and the OP basically say "by having several out of phase antennas you can create constructive interference at the intended receiver of the signal". What am I missing?
    - judk 12y ago
      OP (and also Richard Feybnan) believes that QM provides a more intuitive explanation for the elusive "why" waves (interference) exist. Commenters here don't like that.
namuol 12y ago
Care to point me in a better direction?
- ekianjo 12y ago
  Physics class in college. I agree with the comment. The author has very little idea of the concepts behind radiation and attached phenomena.
- lpmay 12y ago
  I think abstrakraft's comment may partially be a reaction to the informal "fast and loose" style of your article. That said, I think there are also quite a number of factual inaccuracies. I won't go into all of them, but will comment on one paragraph from the article. "(There's another concept called "antenna efficiency" which basically says you can adjust your scoop to resonate at a particular frequency, rejecting noise outside that frequency. That definitely works - but all antennas are already designed for this. That's why you get different antennas for different frequency ranges. Nowadays, the only thing you can do by changing your antenna size is to screw up the efficiency. You won't be improving it any further. So let's ignore antenna efficiency. You need a good quality antenna, but there is not really such a thing as a "better" quality antenna these days, at least for wifi.)" Here you are conflating the issues of bandwidth and efficiency. Efficiency is how much RF power is lost to dissipative mechanisms in the antenna compared to how much is actually radiated. What you go on to describe is the bandwidth of the antenna. Your explanation that the bandwidth of the antenna is somehow chosen to reject noise for the receiver also demonstrates a misunderstanding of how all modern receiver architectures work. The noise bandwidth is either set by an IF filter in a super heterodyne receiver, or in the case of a synchronous digital receiver, in the matched filters. Antenna bandwidth may occasionally be chosen to reject interferes, but this is a different concept entirely. I suspect in consumer wi-fi antennas, if bandwidth is designed at all beyond "enough" it would be to maximize impedance bandwidth to allow for loading. It is also patently incorrect to say that "the only thing you can do by changing your antenna size is to screw up the efficiency". Larger antenna apertures provide more focusing, and therefore more directivity, and for a given efficiency more gain. Considering an array of antennas as a single antenna is one example of this. Another would be dish or horn type antennas which can be made with larger and larger apertures for more and more gain. There are other issues throughout the article, but it's really not my intention to go line by line. It's also not my intention to discourage you from investigating this stuff further. I'm a practicing electrical engineer, and I feel every day all I learn is how much more I have yet to learn. Suffice it to say many of these concepts are very nuanced and complex (more so than your article reflects), so I applaud you for trying to figure this out on your own. Just don't think it will be nearly as simple as learning a new programming language. A couple basic things I would recommend you look up: the difference between directivity and gain, and the difference between coherent vs non-coherent combination. If you can, find someone who really, really knows this stuff to bounce your thoughts off of. Best of luck!

akerl_ 12y ago

Can you elaborate? Without some kind of analysis of the mistakes in the article, we don't really have a way to judge if we should belief your statement about the author, nor can we improve our understanding. A more descriptive listing of some of the issues with the article, or links to better resources, would rock.

madengr 12y ago
Well to start, the antenna generates it's own noise since it is not 100% efficient; i.e. it has a real resistance in addition to it's radiation resistance. If you put a real antenna in a box made of perfect electrical conductor, it would still generate noise, so you really don't halve the noise by increasing the gain 3 dB, you double the signal. Here is a good tutorial on phased arrays. It's actually a lot easier to think of it when receiving a skewed wavefront, and the phase shifters (delay elements) compensating for the delay. http://www.radartutorial.eu/06.antennas/an14.en.html http://www.radartutorial.eu/06.antennas/an14.en.html
- jerf 12y ago
  OK, while that seems like a valid tidbit if one has to implement this stuff, it doesn't seem like that's a helpful complication to introduce when trying to explain the basic concept.
abstrakraft 12y ago
Any time someone appeals to quantum physics to offer a handwaving explanation of something that classical physics covers just fine, watch out. Using path integrals to introduce interferometry is a waste of time, and in this case, just plain wrong. For a better source, I'd start with the wikipedia articles on beamforming, phased arrays, and interferometry (http://en.wikipedia.org/wiki/Beamforming http://en.wikipedia.org/wiki/Beamforming, http://en.wikipedia.org/wiki/Phased_array http://en.wikipedia.org/wiki/Phased_array, http://en.wikipedia.org/wiki/Interferometry http://en.wikipedia.org/wiki/Interferometry).
- MarkSweep 12y ago
  Both the beamforming Wikipedia article and the OP basically say "by having several out of phase antennas you can create constructive interference at the intended receiver of the signal". What am I missing?
  - judk 12y ago
    OP (and also Richard Feybnan) believes that QM provides a more intuitive explanation for the elusive "why" waves (interference) exist. Commenters here don't like that.

namuol 12y ago

Care to point me in a better direction?

ekianjo 12y ago
Physics class in college. I agree with the comment. The author has very little idea of the concepts behind radiation and attached phenomena.
lpmay 12y ago
I think abstrakraft's comment may partially be a reaction to the informal "fast and loose" style of your article. That said, I think there are also quite a number of factual inaccuracies. I won't go into all of them, but will comment on one paragraph from the article. "(There's another concept called "antenna efficiency" which basically says you can adjust your scoop to resonate at a particular frequency, rejecting noise outside that frequency. That definitely works - but all antennas are already designed for this. That's why you get different antennas for different frequency ranges. Nowadays, the only thing you can do by changing your antenna size is to screw up the efficiency. You won't be improving it any further. So let's ignore antenna efficiency. You need a good quality antenna, but there is not really such a thing as a "better" quality antenna these days, at least for wifi.)" Here you are conflating the issues of bandwidth and efficiency. Efficiency is how much RF power is lost to dissipative mechanisms in the antenna compared to how much is actually radiated. What you go on to describe is the bandwidth of the antenna. Your explanation that the bandwidth of the antenna is somehow chosen to reject noise for the receiver also demonstrates a misunderstanding of how all modern receiver architectures work. The noise bandwidth is either set by an IF filter in a super heterodyne receiver, or in the case of a synchronous digital receiver, in the matched filters. Antenna bandwidth may occasionally be chosen to reject interferes, but this is a different concept entirely. I suspect in consumer wi-fi antennas, if bandwidth is designed at all beyond "enough" it would be to maximize impedance bandwidth to allow for loading. It is also patently incorrect to say that "the only thing you can do by changing your antenna size is to screw up the efficiency". Larger antenna apertures provide more focusing, and therefore more directivity, and for a given efficiency more gain. Considering an array of antennas as a single antenna is one example of this. Another would be dish or horn type antennas which can be made with larger and larger apertures for more and more gain. There are other issues throughout the article, but it's really not my intention to go line by line. It's also not my intention to discourage you from investigating this stuff further. I'm a practicing electrical engineer, and I feel every day all I learn is how much more I have yet to learn. Suffice it to say many of these concepts are very nuanced and complex (more so than your article reflects), so I applaud you for trying to figure this out on your own. Just don't think it will be nearly as simple as learning a new programming language. A couple basic things I would recommend you look up: the difference between directivity and gain, and the difference between coherent vs non-coherent combination. If you can, find someone who really, really knows this stuff to bounce your thoughts off of. Best of luck!