287
Mobile Communication Fields in Biological Systems
Great effort has recently been devoted to the intercomparison of experimental compliance procedures (Davis et al. 2006). It is also highly recommended to select relevant and
accurate dosimetry techniques for each purpose and to validate the evaluated dose by
comparing between numerical and experimental dosimetry. For example, in the studies
of Lazzi, Gandhi, and Sullivan (2000) and Nicolas et al. (2001), the feasibility of mixed
experimental/numerical procedures to compute the induced SAR beginning from measured exposure field distributions was studied. For the purposes of uncertainty assessment, a comprehensive investigation in Kainz et al. (2005) compared the SAM phantom
to 14 anatomically correct head models in order to systematically evaluate whether or
not SAM is conservative and assess the corresponding phantom uncertainty.
5.4 Exposure Assessment
5.4.1 Cellular Phones
Since the early 1980s when analog cellular radio systems were introduced in Europe, the
cellular mobile telephone industry has undergone rapid growth. In many countries the
take-up rate is approaching and sometimes exceeding 100%.
Different countries have different cellular phone operating systems and slightly
different frequencies are used. The digital system (global system for mobile communication, GSM) started in 1991 and has, recently, increased to be the most common
phone operating system. This system uses dual band, 900 and 1800 MHz, for communication. From 2003, the third generation of cellular phones (3G), or universal
mobile telecommunication system (UMTS) cellular phones, have started operating
in some countries at 1900 MHz. Other countries are using slightly different systems.
With adaptive power control technology, cellular phones operate at the lowest power
necessary for acceptable communications in order to reduce human exposure to the
radiated EM fields.
5.4.1.1 Cellular Phone Modeling
The way in which cellular phones are modeled varies from plane-wave and simple
monopoles or dipoles to more complicated structures and realistic phone geometries.
While real cellular phones are most commonly used in experimental dosimetry, the
accurate numerical modeling of commercial cellular phones is one of the main challenges in numerical dosimetry. Experimental investigations of the numerical cellular
phone models may also be performed.
Plane-wave illumination of the human body has been considered in the studies of
Lin (1976), Lu et al. (1996), and Sullivan, Borup, and Gandhi (1987), while illumination
by a short dipole (Zhou and van Oosterom 1992) has also been examined. Dipoles of various lengths placed in close proximity to the human head have been analyzed in research
of Chen and Wang (1994), Chuang (1994), Dimbylow and Mann (1994), Hombach et
al. (1996), Karimullah, Chen, and Nyquist (1980), Lazzi, Gandhi, and Sullivan (2000),
Martens et al. (1995), and Meier et al. (1997). Three different numerical models of the
dipole have generally been adopted. The first model is the “infinitely thin wire” approximation, obtained by setting to zero the tangential electric field component along the
Mobile Communication Fields in Biological Systems
Great effort has recently been devoted to the intercomparison of experimental compliance procedures (Davis et al. 2006). It is also highly recommended to select relevant and
accurate dosimetry techniques for each purpose and to validate the evaluated dose by
comparing between numerical and experimental dosimetry. For example, in the studies
of Lazzi, Gandhi, and Sullivan (2000) and Nicolas et al. (2001), the feasibility of mixed
experimental/numerical procedures to compute the induced SAR beginning from measured exposure field distributions was studied. For the purposes of uncertainty assessment, a comprehensive investigation in Kainz et al. (2005) compared the SAM phantom
to 14 anatomically correct head models in order to systematically evaluate whether or
not SAM is conservative and assess the corresponding phantom uncertainty.
5.4 Exposure Assessment
5.4.1 Cellular Phones
Since the early 1980s when analog cellular radio systems were introduced in Europe, the
cellular mobile telephone industry has undergone rapid growth. In many countries the
take-up rate is approaching and sometimes exceeding 100%.
Different countries have different cellular phone operating systems and slightly
different frequencies are used. The digital system (global system for mobile communication, GSM) started in 1991 and has, recently, increased to be the most common
phone operating system. This system uses dual band, 900 and 1800 MHz, for communication. From 2003, the third generation of cellular phones (3G), or universal
mobile telecommunication system (UMTS) cellular phones, have started operating
in some countries at 1900 MHz. Other countries are using slightly different systems.
With adaptive power control technology, cellular phones operate at the lowest power
necessary for acceptable communications in order to reduce human exposure to the
radiated EM fields.
5.4.1.1 Cellular Phone Modeling
The way in which cellular phones are modeled varies from plane-wave and simple
monopoles or dipoles to more complicated structures and realistic phone geometries.
While real cellular phones are most commonly used in experimental dosimetry, the
accurate numerical modeling of commercial cellular phones is one of the main challenges in numerical dosimetry. Experimental investigations of the numerical cellular
phone models may also be performed.
Plane-wave illumination of the human body has been considered in the studies of
Lin (1976), Lu et al. (1996), and Sullivan, Borup, and Gandhi (1987), while illumination
by a short dipole (Zhou and van Oosterom 1992) has also been examined. Dipoles of various lengths placed in close proximity to the human head have been analyzed in research
of Chen and Wang (1994), Chuang (1994), Dimbylow and Mann (1994), Hombach et
al. (1996), Karimullah, Chen, and Nyquist (1980), Lazzi, Gandhi, and Sullivan (2000),
Martens et al. (1995), and Meier et al. (1997). Three different numerical models of the
dipole have generally been adopted. The first model is the “infinitely thin wire” approximation, obtained by setting to zero the tangential electric field component along the