Heating Effect of Mode of Operations of Mobile Phones A D Usman¹, W F Wan Ahmad 2 , T H Su 2 , A Rusnani 3 , Abstract- Bluetooth is a technology that has been widely used for transferring data and files within a short distance range using electromagnetic energy. Hence, it has raised public awareness on the radiation of the Bluetooth devices. This study quantifies the thermal effect by investigating electromagnetic field exposure during and after a call is made using three different mobile phone models, with three different modes of operation. An infrared thermal camera was used to obtain thermal images of the right ear- face region of a human during and after a call is made. It is shown that mobile phone usages with Bluetooth connection contribute the lowest to the right ear-face region surface temperature rise compared to wired hands free and direct contact modes. The right ear-face region temperature rise is found to be the highest using wired hands free. Also, it is demonstrated that exposure to radio frequency electromagnetic field due to the usages of Bluetooth and direct contact modes for all the three mobile phone models are generally below the ICNIRP considered safe levels, while the usage of wired hands free mode is on the contrary. Keywords- Bluetooth, wired hands free, thermal images, RF EMF, ICNIRP. I. INTRODUCTION OBILE phone usages are indispensable in today’s world. Some users of this technology experience warming sensations and itching on the side of the face and headaches. These complain and the search for convenience has made the mobile manufactures to come up with alternatives in making and receiving calls using mobile phones. Nowadays, people use Bluetooth hands free (BTHF) and wired hands free (WHF) in addition to the direct contact between their ear-face regions and the mobile phones. The word Bluetooth is taken from the 10 th century Danish King Harald Bluetooth who was very influential in uniting Scandinavians. The founder of the Bluetooth has felt that the name Bluetooth was fitted as it is meant to unite different devices such as computer and mobile phones [1]. Fig. 1 shows the logo for the Bluetooth. Bluetooth SIG introduced Bluetooth formally to public with its logo designed by a Scandinavian. In the shown logo, it keeps the original name of Bluetooth. The logo unites the runic alphabetic characters “H”, which look similar to an asterisk, and a “B”, which are the initials for Harald Bluetooth [1]. A D Usman si with Department of Electrical and Electronic Engineering, College of Engineering, Kaduna Polytechnic Kaduna, Nigeria W F Wan Ahmad and T H Su are with Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia. A Rusnani is with Faculty of Engineering, Universiti Teknologi MARA, Malaysia. Fig. 1 Bluetooth Logo Bluetooth is an open wireless protocol for exchanging data over short distance from fixed and mobile devices, creating PANs. It was originally conceived as a wireless alternative to RS232 data cables. As it can connect several devices, Bluetooth is able to overcome problems of synchronization [1]. For example, a BTHF can be simultaneously connected to two mobile phones. While, for any WHF, it can only be connected to one mobile phone at once. Nowadays, most people in the world own more than one mobile phone. Hence, it is inconvenient for them to use the WHF. A BTHF will enable them to connect to all mobile phones at once. In other words, they can answer any call from any of the phone while wearing the same BTHF. They can use this while driving as well as it is safe and not against the law. Bluetooth uses a radio technology called frequency- hopping spread spectrum. It can achieve a transfer data rate of 1Mbps. Bluetooth provides a way to connect several types of Bluetooth devices through a secure, globally unlicensed industrial, scientific and medical (ISM) 2.46 GHz short- range RF band width [2]. Regulations and reports as in [2, 3] and [4, 5], respectively, acknowledged evidences suggesting that increasing human exposure to electromagnetic field (EMF), will in turn increase the local temperature of the body. The extent to which this rise in temperature result has not been investigated using wired and Bluetooth technology. Therefore, this study was designed to quantify the heating effect of radio frequency (RF) EMF due to the usages of BTHF, WHF and direct hand held mobile phones using infrared thermal imaging instrument. An infrared thermographic camera (IRTC) was chosen due to the fact that it is noninvasive and can be used to quantify the temperature within a biological system without coming in contact with it. Though no direct investigation of exposure due to BTHF and WHF mobile phones mode of operation, similar studies on thermal effect using IRTC on hands and heads were reported in [6, 7]. Other studies that use thermographic principles to investigate thermal effects using animals as surrogates were reported by [8-13]. II. THERMOGRAPHIC PROCEDURES A noninvasive IRTC (IR SnapShot ® Model 525, Infrared Solutions, Inc.) that operates in the wavebands 8-12 mm with a thermal resolution of 0.1°C was used. The M International Journal of Research in Engineering and Technology (IJRET) Vol. 1, No. 5, 2012 ISSN 2277 – 4378 246