Electronically steerable antenna arrays, commonly called phased arrays, have been in use for several decades. But they are finding increasing adoption in 5G communications, military and automotive radar, and LEO (low earth orbit) satellites. These antenna arrays could be as small as 2 elements or as large as many thousands of elements. And they can steer a precise beam--but without any mechanical movement. This allows them to rapidly scan the sky or hop quickly between targets. Many can also track multiple targets while simultaneously carrying out a search for new targets. All without any physical movement!
So, this is very cool, and it’s an area that many engineers are working on. But implementing these systems can be difficult! A big part of that challenge is that it requires an overlap of disparate skill sets: RF hardware design, software engineering, system design, communications and radar algorithm design, HDL engineering, and antenna design.
Most engineers are not knowledgeable in every one of these fields – and that makes it hard to get started. And this is precisely the situation I found myself in! I am a field applications engineer for Analog Devices in Colorado. When I first started in this role, my focus was primarily on power conversion. That is a need in every design, but I increasingly saw my customers needing help with some of our more complex products. Products such as high speed data converters, transceivers, and RF components that tended to form the heart of their phased array systems. So, I found myself with a large knowledge and experience gap!
At first, I just tried to study as much as I could – and there are certainly a vast number of detailed books and papers written on these topics! But to me, it ended up feeling like a lot of abstract equations and difficult to visualize concepts. Fortunately, this topic is a significant application focus at Analog Devices, so I can learn from experienced experts in these fields. In particular, Bob Broughton and Pete Delos – two technical leaders at ADI, encouraged me to learn by taking a more hands on approach. So, I started hacking evaluation boards together to create simpler versions of these systems. And I even posted some of my early success (and failures…) on YouTube, where I discovered that others were also trying to grow their skillset in these areas.
After building a few simple setups, I found that the theory and equations behind beamforming became a WHOLE lot more interesting to me! Now I could connect those abstract concepts to what I was seeing. For example, plotting a grating lobe in real-time --and being able to move it around-- helped with understanding the math around why grating lobes appear. This kind of hands-on practical experience started to give me an intuitive sense of basic phased array operation. And gave me a starting point to dig into other aspects of these systems.
So that’s what I’d like to do in this blog series! We’ll start with a very simple 2-element array. It is simple, but it will be enough to learn the fundamentals of beamforming. We’ll also learn how to control it all with ADI’s software libraries—something I’m discovering is not to be taken for granted! And we’ll use that simple beamformer to build our own monopulse tracker and FMCW radar. This will be a fairly low-cost setup, and something anyone could do. Then we’ll expand on these concepts by moving to a larger array, using the soon-to-be-released ADALM-Phaser. This will get us into tapering, beam squint, array factors, grating lobes, etc. Maybe even adaptive beamforming and null steering? But we’ll take the concepts one at a time and focus on how you could do this and experience it all firsthand.
After that, if there’s interest, we could go further into our 32 and even 256-element arrays that Analog Devices offers as prototyping developer kits. But I’ll let the comments and interest from you dictate where exactly we should go.
Despite all the interesting applications for phased array systems, the audience intending to learn this topic may be small. Probably very small! So, if you do have any interest in this, please let us know by adding your questions/comments/insights below. I’d love for this to be a more interactive forum where we can learn together. And in particular, I would love for others to also build up and experiment with these concepts. And then share your feedback and experiences. The first several postings here are going to approach this from a fairly low-cost perspective. We’ll just be using the ADALM-PLUTO and a few odds and ends from Amazon. I’ll kick that off in the next posting. But if you’d like to get a head start, find a Pluto and modify it for 2 transmit / 2 receive operation, as shown in this video:
Ultimately, the first setup we experiment with will look like this:
But more on that in the next blog post here! If you have any other ideas for what you’d like to see from our hands-on phased array exercises, please leave a comment below, and let’s discuss!