Improving Cell Phone Performance

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Ever think your friend on the other end of a cell phone call sounds like she's talking through a tin can? 

Thanks to an advanced antenna system developed by a team of Brigham Young University electrical engineers, the annoyance may one day be a concern of the past. 

Led by associate professor Michael Jensen, the team enabled a single, tiny antenna -- like those commonly attached to a cell phone's circuit board -- to receive two separate radio signals over a single frequency, doubling the amount of information transferred. 

Invisible radio signals move back and forth through the air in waves -- the fluctuation is called frequency. When a radio signal reaches a cell phone's antenna, the phone's electronics reproduce the signal into speech. Companies are assigned a range, called bandwidth, in which they are allowed to generate these radio signals. 

"Cell phone service providers like Sprint PCS and Verizon have only a certain amount of radio bandwidth they can use for cell phone technology," said Jensen. "To accommodate the maximum number of customers, they make trade-offs in terms of a cell phone's vocal quality and the reliability of its signal." 

Many calls drop because a cell phone tower has allotted its available bandwidth to customers currently on their phones. Companies also decide how much bandwidth is absolutely necessary to provide vocal quality that's intelligible, but little more, said Jensen. 

"The resource is finite, the company needs to make a profit and they balance that with customer satisfaction," said Jensen, who was joined on the study by postdoctoral researcher Thomas Svantesson and then-doctorate candidate Jon Wallace. "Our technology allows a company to operate more efficiently within these parameters." 

Published in the Institute of Electrical and Electronics Engineers' "Transactions on Wireless Communications," the research explains how polarization, or the alignment of antennas into different planes of direction, can be used to reliably receive multiple radio signals over the same frequency. 

This is good news for manufacturers who will be able to implement the technology without having to attach additional antennas to cell phones -- something they won't do "because it's ugly," said Jensen. Today's cell phone antennas, typically square pieces of metal with a single connection to a phone's circuit board, are embedded in the phone's chassis. 

The new technology would require manufacturers to install a second connection point, effectively adding another antenna without drastically raising manufacturing costs or increasing the size of the phone. 

"From a design point of view, we aren't dealing with a lot of room on these phones," said Svantesson, the postdoctoral researcher on the team who is now pursuing similar interests at the University of California, San Diego. "However, our results indicate that you can use antennas of different polarizations to design more compact antennas. That is something that most likely will be included in future wireless standards." 

Furthermore, the discovery gives cell phone service providers new options as they work to meet the needs of a growing customer base, said Jensen. 

"Doubling the amount of data cell phone service providers can send to a customer's phone would allow them to do a few things," said Jensen. "First, they could improve the vocal quality of the signal itself. Or, they could keep things how they are now but improve the strength of the signal, which would improve battery life. Or third, they could maintain current quality and reliability and increase their number of users." 

Even if providers chose the third route, which Jensen acknowledges makes the most business sense, companies could begin to offer premium services for customers willing to pay extra for additional quality or reliability. 

Before the technology makes its way into cell phones, which could happen in the U.S. market in as quickly as two years, Jensen says customers will probably see it integrated into laptop computers that wirelessly access the Internet. 

Jensen and his team have already presented the technology at academic conferences, exposing other scientists, some from prominent cell phone companies, to their work. The publication of their research in "Transactions on Wireless Communications" places it even further in the public domain. 

"This is how standards are eventually agreed upon and the technologies that 'make sense' are adopted in consumer products," said Jensen. L-3 Communications, a producer of intelligence, surveillance and reconnaissance products, is already funding Jensen's further study in this area. 

Wallace, who is currently working as a postdoctoral researcher at BYU and the Vienna University of Technology, assisted Jensen and Svantesson on the project. 

"Our paper reveals the 'magic' behind using multiple polarizations, which hasn't really been explained well in terms of electromagnetic theory, " he said. "The practical experience gained on the project was invaluable, and I feel that gaining a mixture of theoretical and practical knowledge at BYU has helped me prepare to be a real-world engineer." 

The National Science Foundation, the Swedish Foundation for Strategic Research and the Hans Werthén Foundation supported the research. 

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