How do bluetooth signals travel through the air?

Derek Wasylenko
23 January 2012

Above: Image © JDP90, Wikimedia Commons

Bluetooth signals are used in many modern electronic devices: from mobile phones and computers, to headphones, GPS navigators, gaming consoles and even some modern cars. Bluetooth technologies are becoming more and more popular in electronic devices largely because of their adaptive and compatible nature for wireless communication between devices.

Did You Know? Bluetooth was named after a Danish king, Harald Bluetooth who united Denmark and part of Norway in the 10th century. The name was chosen to reflect both the importance of Nordic countries in the telecommunications industry, and the unification of certain wireless technologies into an accepted standard.

Bluetooth signals are very similar to the wireless signals used in WiFi devices, radio and television broadcasts and mobile phones. These signals are transmitted by electromagnetic radiation, the very same phenomenon that produces light that you can see (the only difference being the frequency of the radiation). Electromagnetic radiation can be thought to travel through air as a wave, similar to waves traveling over the surface of water. Bluetooth frequencies lie within what is referred to as the radio frequency region, specifically in the range 2.40 – 2.48 GHz. This frequency allows the signals to travel short distances through solids such as walls because the radiation only interacts very weakly with the atoms of the wall itself. One of the main differences between Bluetooth signals and other radio signals is that they are very weak. For example, newer cordless telephones operate at a maximum power of one watt (W), mobile phones typically operate below one W, but typical Bluetooth devices operate below 0.0025 W (or 2.5 mW), less than 400 times as powerful. The reason Bluetooth devices are operated at low power is to prevent interference with other devices such as mobile phones and WiFi signals, to conserve power in battery-operated devices and because they are typically used within about 10 meters of the device (cordless computer mice and keyboards, hands-free headsets, etc.).

Did You Know? A major advantage of Bluetooth is the ability to connect up to eight devices simultaneously using a technology called "spread-spectrum frequency hopping". Basically, the Bluetooth frequencies used by each device are constantly changing, up to 1,600 times per second to prevent interference between devices.

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This article was written by Derek Wasylenko, who is a graduate student studying molecular catalysts for water splitting at the University of Calgary. Derek spends his spare time snowboarding and mountain biking.

Derek Wasylenko

Derek is currently a post-doctoral research associate at the University of Washington in Seattle. His current research interests are primarily involved with the design and study of catalytic materials for energy conversion applications. When not in the lab, Derek enjoys reading, hiking, biking, snowboarding, and spending time with family and friends.

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Avatar  mac hon

cool good info helped me with my project