We all know how radio works. Yet when I think about it, I’m still in awe of how those radio waves are created and transported from one place to another through the so-called “ether.” At the heart of this process of creating electromagnetic waves is one component that’s probably the most misunderstood, and often taken for granted. You know what it is: It’s a transducer, an interface, and more of a mechanical device than an electronic one. Yes, the antenna.
We can create spectrally pure modulated signals at high power levels and implement low-noise high gain receivers. However, it is the antenna that does the real work of translating that RF voltage into an electromagnetic (EM) wave at the transmitter, then converting the received EM signal back into an AC signal to be used. Maxwell’s equations explain the process. An electric field produces a magnetic field, and then the changing magnetic field gives rise to an electric field. And so on. The fields support and regenerate one another along the transmission path. Visualize that. The antenna is that reciprocal mechanical device that converts RF energy both ways. What an amazing but mysterious device.
Today working at millimeter-wave frequencies, antennas are things you can hold in your hand and even smaller. While antenna technology is well known today, there is still an elusive quality about it. I call it black magic. And designing an antenna is the act of following well-known mathematical theories, cookbook techniques, and empirical processes. The empirical part is where the innovation comes and the black magic occurs.
Microwave work has produced many innovative antenna types like the horn, parabolic dish, helical spirals, fractal, and many others. But two antenna technologies have emerged as the solution to many of the problems faced in implementing new wireless technologies like 5G cellular, Wi-Fi, and other high-speed digital standards. These technologies, as you probably know, are MIMO and phased arrays.
MIMO uses multiple conventional antennas (and transceivers) to produce spectral diversity and multiplexing that in turn can boost data rate and reliability in a fixed bandwidth. Phased arrays are matrices of antennas to produce high gain and agile beamforming. It is these antenna technologies that are making 5G and other mmWave products possible.
Phased arrays have been around for decades, mostly in military radar. The technology is generally well known, but the components to implement them are now highly developed, making smaller, better-than-ever phased arrays. At mmWave frequencies like 28 and 39 GHz, arrays are very small. Matrices of patch antennas can be fed with low-noise amplifiers, GaN power amps, direct conversion IC transceivers, and digitally controlled phase shifters to produce agile beamforming, and even multiple beams. At frequencies like 60 GHz and 77 GHz, the phased array antenna is small enough to be implemented at the chip level.
Just a few recent product introductions illustrate the growth of the phased array and MIMO. For example, Analog Devices’ AD9371 dual RF transceiver makes it easier to build phased arrays with beamforming at frequencies up to 6 GHz. You can buy Anokiwave’s AWA-0134, a 256-element electronically scanned antenna for 28-GHz 5G applications. They make the front-end chips to implement 26-28 and 39 GHz arrays. Ethertronics’ EC477 Active Steering Processor and the EC624 Active Steering Antenna Switch provide support for up to 8 × 8 MIMO. Movandi makes a new RFIC front-end called BeamX that integrates RF, antenna, beamforming, and control algorithms into modular 5G millimeter wave solutions in 28- and 39-GHz versions. Look for more to come.
Anyway, phased array technology is probably something you didn’t learn in school. Maybe now is the time. Of course, the web is loaded with articles, white papers, and such just a couple of searches away. But don’t overlook the good old-fashioned way—namely, books. One that came to my attention recently is published by Artech House Publishers. It is Phased Array Antenna Handbook, 3rd edition by Robert J Mailoux.
The book has been around for years in previous editions but this recently published one is right up to date with all the latest methods and designs. It covers antennas for radar and communications systems, space and airborne applications, automotive radar, and cellular. The coverage seems to include all the latest methods, devices, and technologies developed in the past few years. Something to consider if you need to learn more.
Anyway, get to know more about antennas, especially phased arrays (and MIMO), as they are here now and the future for many new designs.