I'm Buying My Next Cell Phone in San Francisco

San Francisco's new law requires retailers to post mobile phone radiation levels.

2 min read
I'm Buying My Next Cell Phone in San Francisco

It may take years before researchers figure out whether cell phone radiation carries long-term risks or is completely benign. The Interphone study, released in May, was supposed to settle the matter; it didn’t.

Meanwhile, governments regulate the amount of radiation mobile devices can emit—the Specific Absorption Rate (SAR). They do this because the science is clear on one way radiation can damage cells—by generating heat. Limiting the SAR limits the amount of heat generated to a recognized safe level. Countries differ in how they set these limits; in the U.S., the number is 1.6 watts per kilogram. Researchers are investigating other ways radiation can affect human tissues besides heating them, but this issue has yet to be settled, or reflected in a standard.

Someone like me, who doesn’t want to hide under a rock until cell phones are either given a clean bill of health or proven dangerous, might want to choose a cell phone with as low a SAR number as possible. (They range from 0.1 to the maximum 1.6.) That person might be particularly careful when purchasing a phone for a child—it turns out that children’s brains absorb radiation differently. In recognition of this, a number of European agencies have warned parents to limit their children’s cell phone use.

I set out to find a low-SAR phone the last time I purchased a cell phone. It wasn’t, however, easy to get those numbers, particularly standing inside the store looking at phones. (They can be buried in manuals or data sheets packed with the phones, they sure aren’t on display.) Standing in the store, I spent about 20 minutes on the phone with a customer service rep at a call center, and he managed to eventually find the information. The phone I settled on had a moderate SAR of 0.54.

Apparently, I wasn’t the only shopper frustrated by how hard it is to get this information. This week, the San Francisco board of supervisors passed a law requiring retailers to post SAR data or face a fine. The law goes into effect in February.

The CTIA, the association that represents wireless manufacturers, is not happy about the San Francisco law, the first of its kind in the country. The CTIA says SAR information is irrelevant, and that no phones are safer than other phones. (I suppose CTIA members would rather compete on camera megapixels and apps and music capacity rather than radiation levels.) So it is going to make San Francisco pay—the CTIA is taking its annual trade show, held for the last seven years in San Francisco, elsewhere.

Wow. That’s like the cheese industry freaking out because they have to list fat grams on their labels.

But I can vote with my feet, too. The next time I buy a cell phone, I’ll be going to a retailer in San Francisco.

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.

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