Fractus Antennas Pitches New “Antenna-less” Smartphone Technology

Instead of a dedicated antenna, the company's approach radiates radio-frequency signals from the ground plane

5 min read
A smartphone antenna rests on a platform in the middle of a chamber lined with large blue foam spikes and surrounded by a thick foam ring.
Employees at Fractus Antennas in Barcelona use this anechoic chamber to test new antenna designs. Spikes along the walls absorb stray signals while sensors around the middle ring measure signal performance.
Photo: Amy Nordrum

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.  

The internal workings of three early smartphones show a metallic antenna attached to a plastic surface toward the top of each device.   In these smartphones, the antennas are at the top of the devices and identifiable by a squiggly metal line attached to a plastic mold. The mold is black in the device on the far left and clear in the phone on the far right.Photo: Amy Nordrum

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.

Instead of having an antenna that radiates inside the phone, the phone itself is radiating.

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 Boostera small device roughly one-tenth the size of a traditional antenna. 

Fracus Antennas' antenna booster technology is shown in comparison to conventional fractal-based antennas from smartphones. Fractus Antennas’ new antenna booster comes in several sizes (in green on left) and is one-tenth the size of a conventional fractal-based antennas (on right, removed from smartphones in previous photo).Photo: Amy Nordrum

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.

The Conversation (0)

Metamaterials Could Solve One of 6G’s Big Problems

There’s plenty of bandwidth available if we use reconfigurable intelligent surfaces

12 min read
An illustration depicting cellphone users at street level in a city, with wireless signals reaching them via reflecting surfaces.

Ground level in a typical urban canyon, shielded by tall buildings, will be inaccessible to some 6G frequencies. Deft placement of reconfigurable intelligent surfaces [yellow] will enable the signals to pervade these areas.

Chris Philpot

For all the tumultuous revolution in wireless technology over the past several decades, there have been a couple of constants. One is the overcrowding of radio bands, and the other is the move to escape that congestion by exploiting higher and higher frequencies. And today, as engineers roll out 5G and plan for 6G wireless, they find themselves at a crossroads: After years of designing superefficient transmitters and receivers, and of compensating for the signal losses at the end points of a radio channel, they’re beginning to realize that they are approaching the practical limits of transmitter and receiver efficiency. From now on, to get high performance as we go to higher frequencies, we will need to engineer the wireless channel itself. But how can we possibly engineer and control a wireless environment, which is determined by a host of factors, many of them random and therefore unpredictable?

Perhaps the most promising solution, right now, is to use reconfigurable intelligent surfaces. These are planar structures typically ranging in size from about 100 square centimeters to about 5 square meters or more, depending on the frequency and other factors. These surfaces use advanced substances called metamaterials to reflect and refract electromagnetic waves. Thin two-dimensional metamaterials, known as metasurfaces, can be designed to sense the local electromagnetic environment and tune the wave’s key properties, such as its amplitude, phase, and polarization, as the wave is reflected or refracted by the surface. So as the waves fall on such a surface, it can alter the incident waves’ direction so as to strengthen the channel. In fact, these metasurfaces can be programmed to make these changes dynamically, reconfiguring the signal in real time in response to changes in the wireless channel. Think of reconfigurable intelligent surfaces as the next evolution of the repeater concept.

Keep Reading ↓Show less
{"imageShortcodeIds":[]}