When [Kenneth Keiter] took apart his Starlink dish back in November, he did his best to explain the high-level functionality of the incredibly complex device in a video posted to his YouTube channel. It was a fascinating look at the equipment, but by his own admission, he wasn’t the right person to try and explain the nuances of how the phased array actually functioned. But he knew who could do the technology justice, which is why he shipped the dismembered dish over to [Shahriar Shahramian] of The Signal Path.
Don’t be surprised if you can’t quite wrap your head around his detailed analysis after your first viewing. You’ll probably have a few lingering questions after the second re-watch as well. But that’s OK, as [Shahriar] still has a few of his own. Even after cutting out a section of the dish and putting it under an X-ray, it’s still not completely clear how the SpaceX engineers managed to cram everything into such a tidy package. Though there seems to be no question that the $500 price for the early-access hardware is an absolute steal, all things considered.
Most of the video is spent examining the stacked honeycomb construction of the phased antenna array, which as expected, holds a number of RF secrets if you know what to look for. Put simply, there’s no such thing as an insignificant detail to the trained eye. From the carefully sized injection molded spacer sheet that keeps the upper array a specific distance from the RF4-like radome, to the almost microscopic holes that have been bored through each floating patch to maintain equalized air pressure through the stack up, [Shahriar] picks up on fascinating details which might otherwise seem like arbitrary design decisions.
But a visual inspection will only get you so far. Eventually [Shahriar] has to cut out a slice of the PCB so he can fit it into the X-ray machine, but don’t feel too bad, the dish was long dead before he got his hands on it. While he hasn’t yet completed his full analysis, an initial examination indicates that each large IC and the eight chips surrounding it make up a 16 channel beam forming module. Each channel is further split into two RX and TX pairs, which provides the necessary right and left hand polarization. That said, he admits there’s some room for interpretation and that further work would be necessary before any hard conclusions could be made.
Between this RF analysis and the initial overview provided by [Kenneth], we’ve already learned a lot more about this device than many might have expected considering how rare and expensive the hardware is. While we admit it’s not immediately clear what kind of hijinks hardware hackers could get into once this device is fully understood, we’re certainly eager to find out.
While SpaceX’s constellation of Starlink satellites is nowhere near its projected final size, the company has enough of the birds zipping around in low Earth orbit to start a limited testing period they call the Better Than Nothing Beta. If you’re lucky enough to get selected, you have to cough up $500 for the hardware and another $100 a month for the service. Despite the fairly high bar for getting your hands on one, [Kenneth Keiter] decided to sacrifice his Starlink dish to the teardown Gods.
We say sacrifice because [Kenneth] had to literally destroy the dish to get a look inside. It doesn’t appear that you can realistically get into the exceptionally thin antenna array without pulling it all apart, thanks in part to preposterous amount of adhesive that holds the structural back plate onto the PCB. The sky-facing side of the phased array, the key element that allows the antenna to track the rapidly moving Starlink satellites as they pass overhead, is also laminated to a stack-up comprised of plastic hexagonal mesh layers, passive antenna elements, and the outer fiberglass skin. In short, there are definitely no user-serviceable parts inside.
Beyond attempting to analyze the RF magic that’s happening inside the antenna, [Kenneth] also takes viewers through a tour of some of the more recognizable components of the PCB; picking out things like the Power over Ethernet magnetics, a GPS receiver, some flash storage, and the H-Bridge drivers used to control the pan and tilt motors in the base of the dish.
It also appears that the antenna is a self-contained computer of sorts, complete with ARM processor and RAM to run the software that aims the phased array. Speaking of which, it should come as no surprise to find that not only are the ICs that drive the dizzying array of antenna elements the most numerous components on the PCB, but that they appear to be some kind of custom silicon designed specifically for SpaceX.
No matter what you think of Elon Musk, it’s hard to deny that he takes the dictum “There’s no such thing as bad publicity” to heart. From hurling sports cars into orbit to solar-powered roof destroyers, there’s little that Mr. Musk can’t turn into a net positive for at least one of his many ventures, not to mention his image.
Elon may have gotten in over his head, though. His plan to use his SpaceX rockets to fill the sky with thousands of satellites dedicated to providing cheap Internet access ran afoul of the astronomy community, which has decried the impact of the Starlink satellites on observations, both in the optical wavelengths and further down the spectrum in the radio bands. And that’s with only a tiny fraction of the planned constellation deployed; once fully built-out, they fear Starlink will ruin Earth-based observation forever.
What exactly the final Starlink constellation will look like and what impact it would have on observations depend greatly on the degree to which it can withstand regulatory efforts and market forces. Assuming it does survive and gets built out into a system that more or less resembles the current plan, what exactly will Starlink do? And more importantly, how will it accomplish its stated goals?
Our friend [Hunter Scott] gave a talk at a past Supercon about phased array antennas. He mentioned he was looking for collaborators to create an antenna with the SiBeam SB9210 chip. This is a specialized chip for WirelessHD, a more or less failed video streaming protocol, and it’s essentially an entire 60 GHz phased array on a chip with both transmit and receive capabilities. For $15, it seems like quite the bargain, and [Hunter] still wants to put the device to work.
The downside is that Lattice bought SiBeam and killed this chip — not surprising considering WirelessHD never really took off. However, [Hunter] says the chip was in some old smart TVs and laptops. If you can find replacement boards for those devices on the surplus market, you can get the chip and the supporting circuitry for a song.
If you watch old science fiction or military movies — or if you were alive back in the 1960s — you probably know the cliche for a radar antenna is a spinning dish. Although the very first radar antennas were made from wire, as radar sets moved higher in frequency, antennas got smaller and rotating them meant you could “look” in different directions. When most people got their TV with an antenna, rotating those were pretty common, too. But these days you don’t see many moving antennas. Why? Because antennas these days move electrically rather than physically using multiple antennas in a phased array. These electronically scanned phased array antennas are the subject of Hunter Scott’s talk at 2018’s Supercon. Didn’t make it? No problem, you can watch the video below.
While this seems like new technology, it actually dates back to 1905. Karl Braun fed the output of a transmitter to three monopoles set up as a triangle. One antenna had a 90 degree phase shift. The two in-phase antennas caused a stronger signal in one direction, while the out-of-phase antenna canceled most of the signal and the resulting aggregate was a unidirectional beam. By changing the antenna fed with the delay, the beam could rotate in three 120 degree steps.
Today phased arrays are in all sorts of radio equipment from broadcast radio transmitters to WiFi routers and 5G phones. The technique even has uses in optics and acoustics.
Ultrasonic phased arrays are one of the wonders of the moment, with videos of small items being levitated by them shared far and wide. We’ve all seen them and some of us have even wondered about building them, but what about the practical considerations? Just how would you drive a large array of ultrasonic transducers, and how would you maintain a consistent phase relationship between their outputs? It’s a problem [Niklas Fauth] has been grappling with over the three iterations so far of his ultrasonic phased array project, and you can follow his progress on the latest build.
The arrays themselves are a 16 by 16 grid of cheap ultrasonic transducers on a PCB, fed by HV583 high-voltage shift registers. These chips have proven to be particularly problematic, their drivers having a relatively high internal resistance which leaves them prone to overheating.
An interesting solution to a problem comes from the transducers having a polarity, but because it doesn’t matter in their usual application, that polarity not being marked. He’s overcome this by using the STM32 he has managing power alongside his BeagleBone to listen through a sensor as the ‘Bone supplies each transducer in turn with a known phase. An internal map can then be created, such that the appropriate phase can be applied on a transducer-by-transducer basis.
Before anyone gets to thinking about using this technique to build a hoverboard that actually hovers, it’s best that you scale your expectations way, way down. Still, being able to float drops of liquid and small life forms is no mean feat, and looks like a ton of fun to boot. [Asier Marzo]’s Instructable’s post fulfills a promise he made when he first published results for what the popular press then breathlessly dubbed a “tractor beam,” which we covered back in January. This levitator clearly has roots in the earlier work, what with 3D-printed hemispherical sections bristling with ultrasonic transducers all wired in phase. A second section was added to create standing acoustic waves in the middle of the space, and as the video below shows, just about anything light enough and as least as cooperative as an ant can be manipulated in the Z-axis.
There’s plenty of room to expand on [Asier]’s design, and probably more practical applications than annoying bugs. Surface-mount devices are pretty tiny — perhaps an acoustic pick and place is possible?