A tiny company based in Barcelona is promoting a new technology that it hopes can revolutionize smartphone antennas—by removing them altogether.
The job of any smartphone antenna is to radiate a radio-frequency signal generated by the phone’s transmitter out to the nearest cellular base station or Wi-Fi router. Now, Fractus Antennas wants to replace that antenna with a much smaller component called an antenna booster—a tiny lightweight cube made of a metal frame and FR-4 epoxy, the same material used in printed circuit boards.
The company says it can use this booster, along with some modifications to the smartphone’s circuitry, to radiate RF signals exclusively from a device’s ground plane—with no dedicated antenna to speak of. According to the company, this approach can deliver performance comparable to today’s smartphone antennas, at a lower cost for manufacturers.
During this year’s Mobile World Congress, the smartphone industry’s largest trade show, Carles Puente, Fractus Antennas’ cofounder and vice-president for innovation, quietly wandered the exhibit halls and handed out samples of this antenna booster from his satchel to any smartphone maker who might be able to use it.
Back at his office near Barcelona, Puente compared it to a few antennas found in smartphones over the past decade. He pulled several devices from storage that were left over from the time his first company, Fractus, which also specializes in antennas, sued 10 manufacturers for patent infringement. He and his staff broke open more than 600 smartphones to build their case, so they’ve seen more than their share of internal antennas.
To explain how the booster technology from his new company, Fractus Antennas, works, he first showed me antennas from a 2008 Blackberry Pearl and a Pantech C740 from the same year. With the casing removed, it was easy to see that both models had what looked like a tangle of metallic lines toward the top of the device. Those squiggly patterns were mounted to plastic structures that gave the antennas a shape designed to help them radiate energy most effectively.
Puente told me these antennas are all inspired by fractals, a type of design in which similar patterns repeat themselves at various sizes. Fractals are naturally found in broccoli stalks and tree branches. With a fractal-based design, smartphone manufacturers can use all or just part of an antenna to provide service across many frequency bands.
For example, one of the longest wavelengths that smartphones must support is for the 698-megahertz frequency, where waves measure 430 millimeters long. And because the size of a radio wave corresponds to the size of the antenna needed to transmit it, longer wavelengths require larger antennas.
A typical smartphone antenna might only be 40- to 60-mm long, so transmitting waves that long requires the antenna’s entire surface. Since smartphones must also provide service across five or six other frequencies, smaller chunks of the same antenna are used to transmit those shorter wavelengths.
Fractus Antennas is a spinoff of Puente’s first company, which patented the use of fractal-based antennas in smartphones (and eventually filed that 2009 lawsuit for patent infringement). For many years, those were the dominant type of antenna found in smartphones.
More recently, manufacturers have moved away from fractal-based antennas and simply placed a metal band along the top of the smartphone to serve as an antenna. But one drawback of these metal bands is that they can’t easily support multiple frequencies at the same time on their own.
Manufacturers must add another part—an active tuner—to generate signals at the frequencies required for carriers around the globe. Still, this tuner is best at providing service at either one band or another, rather than over multiple bands at once.
Meanwhile, the industry is moving toward interband carrier aggregation, in which a device combines spectrum from several frequency bands to build a channel with more bandwidth than would otherwise be available. If metal band antennas can’t simultaneously provide service across bands, they may not be very useful as carrier aggregation becomes more popular.
This is where Fractus Antennas’ new, “antenna-less” smartphone technology comes in. Instead of relying on a dedicated antenna to radiate an RF signal, a handset would radiate the signal directly from the ground plane, which is the copper layer that underlies the phone’s printed circuit board. To do this, the phone’s manufacturer would replace the antenna with Fractus’s mXTEND Antenna Booster, a small device roughly one-tenth the size of a traditional antenna.
It works like this: Once the transmitter generates a signal, it travels through the matching network, which is a part of the smartphone that acts like a tuner to support service at various frequencies. From there, it travels to both the booster and the ground plane. The booster is a passive device that does not radiate at all. Rather, it temporarily stores the signal it receives and repeatedly bounces it over to the ground plane, which radiates it out.
Already, today’s smartphones use the ground plane to radiate a portion of the signal that smartphones produce. To prevent interference, their circuit boards incorporate shields to protect elements that may be vulnerable. However, the Fractus Antennas concept takes this to the next level by using the ground plane to produce all of the radiation that is broadcast to the cell tower or Wi-Fi router. “Instead of having an antenna that radiates inside the phone, the phone itself is radiating,” Puente says.
The antenna booster does require a slightly more complicated matching network than usual. Puente says the matching network of a phone with an antenna booster would include six or seven components rather than the one or two found in a smartphone today—and the network must be redesigned for each model.
Fractus Antennas is now selling several versions of its antenna booster, which can support cellular communications across 12 frequency bands (from 698 MHz to 2690 MHz) and can also be adapted for Wi-Fi and Bluetooth. The company launched in 2015, and its first sales came in 2016.
So far, Fractus Antennas has sold hundreds of thousands of units to a dozen clients who are using them to track fleets of trucks and outfit sensors for smart metering, among other things. Right now, it costs Fractus Antennas about US $1 to produce each unit, but Puente expects they could reduce that cost considerably by producing higher volumes.
The company is not claiming that the booster improves performance; in the company’s tests, it has shown its performance to be similar to that of today’s smartphones. Puente believes its main selling point will be the money that smartphone makers can save by never having to design and manufacture their own antennas again.
If manufacturers sign on, Puente predicts that it may be 2018 before Fractus Antennas’ technology is available in a smartphone. That, he says, is thanks to the devices’ long development cycles. The 15-person company is an underdog in the industry that generates annual revenues of more than US $400 billion worldwide. But as Puente learned from his first company, a few strong patents can take a company far.