Phased Array

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...

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 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.

This is a great series on YouTube, related https://www.youtube.com/watch?v=igrN_wd_g74

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.

You can build one yourself (sort of): https://news.ycombinator.com/item?id=22109708

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

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

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.

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.