Starlink doesn't get enough credit for their phased arrays terminals, I think. They've managed to make a performant antenna for 10 to 100 time less cost than the competition. Without that, the whole system wouldn't be such a success. This article goes into some details. It's the first truly mass produced RF phased array, and the fact that they've shown it's possible will have some big impacts on certain fields (SATCOM obviously, mobile networks, etc).
Maybe it's the first use of phased arrays for consumer satellite data terminals, but I believe phased arrays were mass-produced (and still are) for radar chips -- e.g. in automotive. Ran across this fascinating article on the history:
Good point. To my knowledge most of these radars are MIMO, which are more capable than phased arrays but it's a different architecture. Also these radar systems usually have on the order of 10 antenna elements (although this number is increasing), whereas the starlink terminal has something like 1000 antenna elements, if I remember correctly.
The same principle is used with loudspeakers to create beamforming arrays, albeit at sonic frequencies.
Beamforming speakers in acoustic applications are quite useful and often found in protected monuments or churches since it allows you to "aim" the acoustic energy mainly at the audience and to a lesser degree onto reverberating surfaces which you may not be willing (or allowed) to change by adding acoustic treatment. Nowadays these arrays are also often used at bigger (e.g. outdoor) stages to avoid shooting into the (complaining) neighbourhood.
An interesting side note is also that the principle also works in reverse for the receiving side, so you can have array microphones that can steer the beam of their "focus", either as a column or as a 2D-array that is ceiling mount (like the Sennheiser TCC2). All these arrays show there limits as frequencies go lower tho, so that is something to check for.
Indeed. Another advanced implementation of the concept (other than Danley unity/synergy horns and other diffraction-based solutions like the Seas DXT) is Keele's C(constant) B(eamwidth) T(ransducer):
A phased array radar for light planes was developed privately in 1973, but suppressed with a secrecy order. The USAF didn't have aircraft-sized phased array radars yet. [1]
During my time at university, I nearly overheated my PC while running a genetic algorithm for Phased Array beam optimization. The code was poorly written and far from optimized, the results were underwhelming, but it turned out to be a valuable and amusing learning experience.
As an ham operator, I should use something similar to create a 2m phased array. It would be fun to see if the reality matches the simulations.
The article (and what is generally talked about with phased arrays) generally focuses on radio wave based phasing. This is pretty inaccessible to average hacker. However it works just as well with audio, and can be rigged up much more easily. You can get quite solid results and learn quite a lot about DSP in general
Beam-forming microphones are quite common. 1D ones are very common for desktop use. 2D ones are ceiling-mounted for conference rooms. This one has 96 microphones. [1] There are even systems which record all the inputs from several hundred small microphones and beam-form later, so an observer can later listen in on any conversation in the room. At least one of those was installed in a prison cafeteria.
It's something on my bucket list actually, build a phased array of _something_. Sound indeed sounds (hmm) simpler. Can you recommend any materials for a noob, with a solid STEM background? Many thanks!
You want to start with narrow band. So object tracking, where the object is emitting a single frequency is a great start.
i think at 2khz (it is blazingly irritating to listen to), you need to space your microphones about 15cm apart. so you don't need too much room. Then it's just hooking up 4-6 microphones to a wooden board. Sampling with a decent microprocessor. You can do the processing on board, or ship it to a laptop, and do the processing there.
Just take care with your microphones and sampling. Any large defects will greatly inhibit your results.
Then for the algorithm, do a delay and sum. it's the dumbest approach, but the easiest to understand, and should work
i am somewhat surprised that the Wikipedia article doesn't mention ham radio examples of phased arrays.
A four square is four vertical antennas than be pointed electronically in four different directions. They are used generally on the 80 meter band where the dimensions of a regular beam and the tower heights required make them generally unacceptable to build.
One thing I missed at first is that a phased array uses multiple spherical waves, but the result is actually a plane wave. Knowing this, how it works actually becomes a lot clearer.
PA and multi elements are not limited to forming beams; they can also be used to focus on a specific point on the medium, or do multiplexed beams and use the beams interferences for inspections, etc.
Starlink doesn't get enough credit for their phased arrays terminals, I think. They've managed to make a performant antenna for 10 to 100 time less cost than the competition. Without that, the whole system wouldn't be such a success. This article goes into some details. It's the first truly mass produced RF phased array, and the fact that they've shown it's possible will have some big impacts on certain fields (SATCOM obviously, mobile networks, etc).
https://lilibots.blogspot.com/2021/01/why-is-starlink-termin...
Maybe it's the first use of phased arrays for consumer satellite data terminals, but I believe phased arrays were mass-produced (and still are) for radar chips -- e.g. in automotive. Ran across this fascinating article on the history:
https://www.microwavejournal.com/articles/20469-automotive-r...
Good point. To my knowledge most of these radars are MIMO, which are more capable than phased arrays but it's a different architecture. Also these radar systems usually have on the order of 10 antenna elements (although this number is increasing), whereas the starlink terminal has something like 1000 antenna elements, if I remember correctly.
>. for radar chips -- e.g. in automotive.
The hacker in me is dying to know what the starlink antenna could pe re-purposed to do in terms or radar.
Has anobody tried it or at least did the math of what it could do in that regard?
As long as you can position yourself behind the phase-shifters and the frequency is high enough (usually > 10GHz) it should be fairly easy to do.
They were also produced for WirelessHD enabled TVs in the late 2010s. I.e the SiBeam SB9210 chip
The article refers to starlink as “under construction as of 2021” and references a 2015 interview. It’s a bit outdated.
Doesn't WiFi AC do beam forming?
The same principle is used with loudspeakers to create beamforming arrays, albeit at sonic frequencies.
Beamforming speakers in acoustic applications are quite useful and often found in protected monuments or churches since it allows you to "aim" the acoustic energy mainly at the audience and to a lesser degree onto reverberating surfaces which you may not be willing (or allowed) to change by adding acoustic treatment. Nowadays these arrays are also often used at bigger (e.g. outdoor) stages to avoid shooting into the (complaining) neighbourhood.
An interesting side note is also that the principle also works in reverse for the receiving side, so you can have array microphones that can steer the beam of their "focus", either as a column or as a 2D-array that is ceiling mount (like the Sennheiser TCC2). All these arrays show there limits as frequencies go lower tho, so that is something to check for.
Indeed. Another advanced implementation of the concept (other than Danley unity/synergy horns and other diffraction-based solutions like the Seas DXT) is Keele's C(constant) B(eamwidth) T(ransducer):
https://www.xlrtechs.com/dbkeele.com/CBT.php
https://www.xlrtechs.com/dbkeele.com/images/Card%20Back%20La...
https://www.audiosciencereview.com/forum/index.php?threads/c...
A phased array radar for light planes was developed privately in 1973, but suppressed with a secrecy order. The USAF didn't have aircraft-sized phased array radars yet. [1]
[1] https://books.google.com/books?id=NWzlTqj0gQ4C&pg=PA64#v=one...
The phased array is also an essential element in the improvement of ultrasound scans and non-disruptive ultrasonic testing of composite materials.
It's an exciting technology that has a much wider impact than telecoms.
During my time at university, I nearly overheated my PC while running a genetic algorithm for Phased Array beam optimization. The code was poorly written and far from optimized, the results were underwhelming, but it turned out to be a valuable and amusing learning experience.
As an ham operator, I should use something similar to create a 2m phased array. It would be fun to see if the reality matches the simulations.
The article (and what is generally talked about with phased arrays) generally focuses on radio wave based phasing. This is pretty inaccessible to average hacker. However it works just as well with audio, and can be rigged up much more easily. You can get quite solid results and learn quite a lot about DSP in general
Beam-forming microphones are quite common. 1D ones are very common for desktop use. 2D ones are ceiling-mounted for conference rooms. This one has 96 microphones. [1] There are even systems which record all the inputs from several hundred small microphones and beam-form later, so an observer can later listen in on any conversation in the room. At least one of those was installed in a prison cafeteria.
[1] https://www.nearity.co/products/ceiling-array-microphone-a50
It's something on my bucket list actually, build a phased array of _something_. Sound indeed sounds (hmm) simpler. Can you recommend any materials for a noob, with a solid STEM background? Many thanks!
You want to start with narrow band. So object tracking, where the object is emitting a single frequency is a great start.
i think at 2khz (it is blazingly irritating to listen to), you need to space your microphones about 15cm apart. so you don't need too much room. Then it's just hooking up 4-6 microphones to a wooden board. Sampling with a decent microprocessor. You can do the processing on board, or ship it to a laptop, and do the processing there.
Just take care with your microphones and sampling. Any large defects will greatly inhibit your results.
Then for the algorithm, do a delay and sum. it's the dumbest approach, but the easiest to understand, and should work
i am somewhat surprised that the Wikipedia article doesn't mention ham radio examples of phased arrays.
A four square is four vertical antennas than be pointed electronically in four different directions. They are used generally on the 80 meter band where the dimensions of a regular beam and the tower heights required make them generally unacceptable to build.
http://tm1o.free.fr/4SQ/80m/en_ver_final4-sq_03_04_15.pdf
This is a great series on YouTube, related https://www.youtube.com/watch?v=igrN_wd_g74
You can build one yourself (sort of): https://news.ycombinator.com/item?id=22109708
One thing I missed at first is that a phased array uses multiple spherical waves, but the result is actually a plane wave. Knowing this, how it works actually becomes a lot clearer.
PA and multi elements are not limited to forming beams; they can also be used to focus on a specific point on the medium, or do multiplexed beams and use the beams interferences for inspections, etc.
Yeah the intuition, is that the sphere of the signal is so large, that any small section of it can be approximated to a plane