Ever wonder why your wireless router has a bunch of antennas on it these days and what MIMO really stands for and what it does? Hackaday has a recent article about a group at the MIT Lincoln Laboratory who have come up with a way to visualize how phased array antennas work.
Phased array antenna systems are at the cusp of ubiquity. We now see Multiple-Input Multiple-Output (MIMO) antenna systems on WiFi routers. Soon phased array weather radar systems will help to predict the weather and keep air travel safe, and phased array base stations will be the backbone of 5G which is the next generation of wireless data communication. But what is a phased array antenna system? How do they work? With the help of 1024 LEDs we'll show you.
[...] How Do Phased Array Antenna Systems Work?
How do you create a 'beam of microwave energy' and direct your receiver onto just the right point in space?
An excellent tutorial is presented here, but the key take away is that if we feed an array of antenna elements with the same microwave signal then we can use these elements to direct (or steer as it is commonly referred to) a microwave beam anywhere in space. This beam steering is achieved by the use of a phase shifter (or its equivalent) in series with each and every antenna element.
To make the above explanation more interesting and understandable, friends of mine at MIT Lincoln Laboratory created this direct visualization of how antenna arrays work (shown recently at the 2016 IEEE International Symposium on Phased Array Systems and Technology). It is almost as if you were to put on a pair 'microwave goggles' and looked into the antenna array!
[...] With this visualization system, you can manually move the antenna beam around with a joystick and view the lighted pattern and beam plots changing in real-time, providing an instant and intuitive understanding of phased array beam steering and beam patterns. Absolutely amazing!
(Score: 2) by VLM on Monday January 09 2017, @02:16PM
Click on the link, there's a gif in the comments that does a better job than the entire article by "AKA the A" using a probably stolen gif by Christian Wolff
For a good time I can think of at least two good analogies to phased arrays, one is the classic quantum physics double slit experiment (which sounds like a pr0n video) now imagine how you'd mess with the phases of the slits to steer the resulting interference pattern on the display screen... The other analogy which is closer is you're building a high res radio astronomy interferometer. Unfortunately I think the good analogies are more complicated than the simpler phased array example is directly. Still if you understand a phased array, well then you're like 10 seconds away from understanding a radio astronomy interfereometer is a just a two element (well, sometimes more) phased array.
There are infinite hydrodynamic analogies in electronics and if you measure the instantaneous height of two boats on a dock as waves come in, if you know the angle between the physical boats with a little trig you can figure out the angle of the incoming waves by comparing relative heights at various instants.
You can get super handwavy that a stereotypical aluminum TV antenna from the last half century or so is a phased array of antennas that happens to be made of aluminum and thus can't be steered electrically like a phased array, but imagine if the antenna could change shape (as some expensive ham radio antennas can) then it makes a steerable antenna. Although that's not a perfect analogy.
(Score: 1) by khallow on Monday January 09 2017, @06:55PM
The other analogy which is closer is you're building a high res radio astronomy interferometer.
Yea, the catch, as I understand it, is that radio interferometers are very directional (often using parabolic and/or helical antennas to get additional gain from the given direction), aimed in the same direction often with a scary level of precision, and carefully wired up so the travel path is the same length for each antenna of the group. So it's a very specialized sort of phased array and passive, aside from the aiming of the antennas.
You can get super handwavy that a stereotypical aluminum TV antenna from the last half century or so is a phased array of antennas that happens to be made of aluminum and thus can't be steered electrically like a phased array, but imagine if the antenna could change shape (as some expensive ham radio antennas can) then it makes a steerable antenna.
That's a variation of the Yagi antenna [wikipedia.org]. It's not a true phased array because there is only a single receiving element on the antenna. The rest only serve to boost the signal received on that.
An analogy here would be a modern bathroom stall or shower. The enclosure creates a resonance cavity which allows certain frequencies to persist and dampens nearby frequencies. If instead of a stall, you had suspended in air a series of such wall plates at equal spaced intervals and put a listener in between a pair of these plates (suspended likewise, of course). Then certain frequencies of sound will form standing waves between these plates (namely sound waves where null points coincide with the wall plates physical positions). That in turn will allow you to hear sounds of the appropriate frequency better than normal (though at the cost of a drawn out resonance).
The listener is the actual receiver and the plates just serve as a passive means to trap sound waves of the appropriate frequency. Similarly, the tines (or "parasitic elements") of the Yagi antenna serve as the basis of a resonance trap for radio waves scattering other frequencies.
The typical, old school, Yagi-like TV antenna has many tines of different lengths and spacing. This allows for a greater frequency sensitivity than the traditional Yagi antenna which is narrow frequency.
Another phased array to consider is a typical multi-speaker system, especially, anything like surround sound or the wall of speakers. They are rudimentary systems, but they do allow for tricks like making sounds appear to come from different directions.
(Score: 2) by Osamabobama on Tuesday January 10 2017, @12:11AM
It looks like you are trying to describe a log-periodic antenna [wikipedia.org]. The different length elements expand the frequency range over which it is useful, as each length is tuned to a specific frequency.
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(Score: 1) by khallow on Tuesday January 10 2017, @08:23AM
Electrically, it simulates a series of two or three-element Yagi antennas connected together, each set tuned to a different frequency.
(Score: 2) by donkeyhotay on Monday January 09 2017, @03:09PM
I worked on phased array systems when I was in the Navy, in the 80s. It's interesting to see this technology make it's way into the private sector.
(Score: 3, Interesting) by EvilSS on Monday January 09 2017, @05:34PM
(Score: 0) by Anonymous Coward on Monday January 09 2017, @05:34PM
This link was given in one of the comments on TFA:
http://www.nutaq.com/blog/mimo-radar-and-phased-array-radar [nutaq.com]
(Score: 1) by khallow on Monday January 09 2017, @08:28PM