You probably have never even thought about the radio waves passing through your living room. They're being hurled at you by your Wi-Fi router. Your phone is grabbing them. Some of them come from your neighbor and their baby monitor. The garage door opener down the street, the smart thermostat upstairs, the Bluetooth earbuds on the counter in the kitchen. They all yell at the same invisible ocean.
And somehow, most of the time, it just works.
That “somehow” is RF engineering. And those with it for a living might tell you the ocean is getting somewhat crowded.
You treat the radio frequency spectrum like you would beach front property. Some of it is beautiful, useful art. Much of it is swampland and cannot be easily developed on. And there are only a limited number of these to go around. Most of that signal is between about 30 megahertz and 300 gigahertz, what we most often think of as usable frequency, and inside that sits every call you’ve made, every TV broadcast ever transponded, and every GPS signal that got you out of a wrong turn.
The Federal Communications Commission (FCC) auctioned off a slice of the C-band a few years ago for $81 billion. Eighty-one billion dollars. For air. To be licensed for bits of frequency that no eyes have seen, no hands have touched, and nobody will ever hold. And that number is indicative of how important this stuff has become and how difficult the fight for it truly is.
Then you stir in the 5G networks spreading across towns, like so many flower petals, the satellite constellations like Starlink first scattering tens of thousands of new transmitters into lower orbit ( hundreds at a time), and the ever-opulent Internet of Things that needs billions more connected devices on sub-six frequencies, and things begin to melt down. The need is always increasing year after year, but spectrum stays constant. That all must coexist without anyone stepping on someone else’s signals, which falls upon RF engineers.
Two signals at the same place at the same time on the same frequency will fight. The stronger wins; the weaker is reduced to static, gobbledygook, or dissociation. That’s the simple version. The real version is messier.
Your microwave oven leaks energy at a frequency of 2.4 gigahertz, conveniently the same band your old Wi-Fi router operated on. Now you know why every time someone needs popcorn; your video call freezes. In fact, LED light bulbs have been found to interfere with AM radio reception in some setups. A badly shielded laptop charger can dump EM gunk onto a band, overwhelming any weaker signals in the vicinity.
RF engineers have to design over all of it. They use filters to cut unwanted frequencies. They also employ shielding that prevents noise from coming in or from leaking out. They select modulation systems that can extract a signal out of noise the way you and I might identify a familiar voice at a busy restaurant. When those tricks are not effective enough, they jump. Bluetooth uses a technology called frequency-hopping spread spectrum that can jump between 79 different channels as many as 1,600 times per second. If a jam occurs on one channel, it is already on another one before the interference manages to do some real damage.
That’s peacetime engineering. This is where it all gets really interesting: the defense side.
Accidental interference is what Civilian RF manages. Engineering Military RF is built around individuals who are trying to prevent your signal from getting through. There is a difference and it dramatically impacts how the systems get constructed.
In electronic warfare, one side is trying to get out of the spectrum. The other side is denying it. The most straightforward device, of course: if you beam sufficient power against the correct frequency, you are capable of swamping an adversary’s communications and blocking his radar or GPS control. In Ukraine, Russian forces employed GPS jamming so aggressively that commercial pilots flying near the Black Sea regularly lose navigation signals. Civilian aircraft. Hundreds of miles from the conflict itself. This is the cascading impact of 21st-century electronic warfare, and it is no longer just hypothetical.
Anti-jam design is the answer to jamming and where some of the coolest RF engineering occurs. The systems that can survive in this contested environment use a number of clever tricks at once. They transmit over the entire band, so a jammer would have to hammer lots of frequencies at once to jam them and that takes a lot of power. And instead of antennas that pick up all around in every direction, they use directional antennas which listen in narrow cones. They authenticate signals so that even a correctly tuned fake transmission is rejected. And they leap, over and over again, sometimes thousands of times a second, across patterns that are random-looking to anyone who is missing the right key.
It was designed that way for a reason: The MUOS was borne out of the U.S. military’s need for secure voice and data communications to forces across the globe and deliberately built to function in hostile environment, such as jamming signals. It operates a wideband signal, which is difficult to jam without massive jamming power, and it is designed to operate in the type of dense contested electromagnetic environments modern combat creates. Five satellites cover the globe. Building and launching each one sets you back about $1 billion. It is the cost of effective communications when someone is working against you.
Radar is one of the original types of RF tech and it too has a kind of version of this same problem. The radar broadcasts a pulse of radio energy into the environment and waits for the echo to return. Easy enough in 1940. Much tougher in 2026 when the bandwidth is crammed full of other transmitters, distractions and adversaries who really would rather you not see them at all!
Today, modern radar employs active electronically scanned array, or AESA technology. An AESA radar is not just one big antenna that physically rotates to sweep the sky but contains thousands of small transmitter-receiver elements that can each steer their beam electronically. To detect small or stealthy targets, the radar can scan multiple directions simultaneously while changing frequencies instantaneously to avoid jamming and altering its power output and waveform. That is how it is with the AN/APG-81 radar for the F-35 fighter. So is the SPY-6 radar now being installed at an unprecedented scale across the Navy's newest destroyers. These are not gradual upgrades over older radar. These are a whole new kind of machine.
And all of these systems have to coexist in the spectrum with civilian users. The exact same frequencies that a Navy radar might use can overlap with those of weather radar, satellite downlinks, or 5G cellular bands. The engineering challenge is not only using radar. It’s getting the radar up and running without frying the airliner hundreds of miles away or jamming the cell tower over in the next county. Coordination is a field of engineering in and of itself, which is why modern RF design is often as much about spectrum management as it is antenna design.
Here is an example of a kind of RF engineering you usually do not get to see. The antenna is only as good as the structure that protects it. Anything that sprays rays needs a cowl to protect it during wet weather, ice storms and impacts with rain, ice, debris or birds zipping through air at high speed. The coating is known as a radome and fine-tuning one is more difficult than you might think.
Since radome needs strength balancing weight, it is tough in physical structure. It also needs to be electromagnetically transparent, i.e. radio waves at the antenna's working frequency should pass through it as though it were not present at all. Those two requirements pull in opposite directions. The materials that are hardest to penetrate typically absorb or scatter RF energy. The most transparent materials are often brittle. Composite engineers devote their entire careers to find that sweet spot, and the answer can vary wildly based on frequency, platform speed, local thermal environment, even what a particular threat system must defeat.
Advanced materials such as quartz fiber, fiberglass, or specialty ceramics and bonding polymers enable composite radomes to operate at frequency ranges from a few hundred megahertz up through millimeter wave bands while resisting the brutal physical forces endured by virtually any combat aircraft and shipboard radar. Sea spray, salt corrosion, and gun blast overpressure takes its toll on the radomes of a destroyer’s SPY radar, as well as decades of weather. Meanwhile, the radomes on a hypersonic vehicle have to contend with all of that while also standing up to surface temperatures that can melt aluminum. Different problems. Different materials. Same engineering discipline.
There are a few trends, however, that are pulling RF engineering in directions that would have sounded like science fiction just a generation ago. Out of them, one is cognitive radio. It is very simple concept, instead of having radio that works on a fixed frequency it builds itself to sense the surrounding spectrum and selects the cleanest channel available in real time. The radio thinks for itself. When a band fills up in an instant, it goes. If interference appears, it adapts. Cognitive radio has been a research topic with the Defense Advanced Research Projects Agency for more than 10 years, and the technology is moving towards operational systems now.
Software-defined radio is another one. Back in the day, radios were built with a lot more rigid hardware that was only capable of one thing. Software-defined radio replaces most of that hardware with software, so the same physical box can be dozens of different radios depending on the code loaded. That kind of flexibility is hugely important in a defense scenario, as it means that one piece of hardware can be reprogrammed to receive and address new threats, frequencies or mission requirements on location without anyone needing to ship out different hardware.
And then there is this migration to high frequencies. Three decades ago, the millimeter wave bands above 30 gigahertz were nearly free out of concern that signals don’t propagate for long distances and are absorbed almost entirely by rain, oxygen and anything else in between. However, those same characteristics are now becoming virtues. This also translates to short-range allowing for less interference with more distant systems. Higher frequencies imply huge bandwidth which implies bigger data rates. 5G networks being rolled out in big cities play the gigabit speed card by using millimeter wave bands for short distances, so military systems are taking the same route starting with some high-bandwidth (not necessarily network) applications that in effect trade range for capacity.
RF engineering is not particularly celebrated like artificial intelligence, or quantum computing gets. Nobody makes movies about Antenna design. By definition, it is invisible work; the whole point is that some signals get through, devices connect, radars see, and communications hold under duress. RF engineering goes to work when it works, you hardly notice. You only just make your call, your GPS persists, and weather radar captures the storm in time.
But every year the spectrum gets more crowded. The threats are more sophisticated. And the systems built on top of those radio waves have never been more essential to either day-to-day functioning or national security. And the engineers fighting that invisible battle are doing some of the most unheralded work nobody will ever see.
The next time that your phone connects cleanly when it is one of 60,000 doing so inside a stadium, somebody worked for that. Quietly.
Responsive anti-jam communications that continue to function even when adversaries are attempting to jam.
Adaptive radar for scanning, tracking and identification through interference & decoys
Techniques that allow the coexistence of civilian and defense systems on the same packed bands called spectrum-sharing
The radio spectrum is finite, hotly contested, and more critical than ever. The engineers that keep signals flowing through the noise are practicing an invisible craft that binds the world of today together.
Get ready to be at the bleeding edge of advanced composites, aerospace materials and defense engineering, including radomes and structures that allow RF systems to do their work in environments that would ruin lesser materials; it’s what Mentis Sciences works on. The unseen fight for the spectrum takes place within hardware that few understand.
