40
Electromagnetic Fields in Biological Systems
• The RF energies are transferred back and forth between the source (antenna) and
the body.
• The SAR level inside the body is influenced by direct interaction of the source with
the body.
• The electric field effect is weaker since dielectric permittivity of tissue is relatively
high.
• Inductive coupling of wireless antenna current–generated magnetic field dominates field coupling and power deposition or energy absorption.
• The SAR value varies with specific antenna configuration and the placement of
the antenna next to the head or body.
• Anatomy of the head and tissue inhomogeneity can influence the maximum value
and distribution of SAR in the head of a mobile telephone user.
• Integrated SAR (or average SAR) in the body is similar for both homogeneous and
inhomogeneous models.
• A large fraction (40%–50%) of the radiated RF power is absorbed by the human
body (including the head).
• The bulk of power deposition occurs on the side of the head nearest to the radiating structure of the cellular telephone.
• The SAR distribution follows an exponential trend away from the antenna side
and it is considerably lower elsewhere in the head of a cell phone user.
• Maximum SAR and its distribution in the head are functions of distance of the
radiating element from the skin surface and the current distribution on the
antenna.
• For a comparable level of electric field to be induced inside the body or a model by
an ELF magnetic field, the applied ELF electric field must be 120π times greater
than the electric field of a plane wave.
1.12 C oupling of Short and Ultra-Wideband
Pulses into the Human Body
The biological effects of electromagnetic pulses (EMPs) of varying durations have
long been investigated in research laboratories. Electromagnetic pulses with electric fields ranging from 20 to 500 kV/m or higher and with frequency spectra of
0–80 MHz are produced by nuclear EMP simulators. They are used to assess the
electromagnetic compatibility or immunity of electronic instruments and systems
under the conditions of a nuclear burst. However, it is only during recent years that
the benefit and capability of the large bandwidth provided by very short or ultrawideband (UWB) EMPs are being considered for imaging, sensing, and communication applications (Di Benedetto et al. 2006; Lin et al. 2008). Examples of applications
include biomedical imaging; vehicular radar; ground-penetrating radars (GPRs);
through-wall sensing; and communications systems such as handheld transceivers,
sensor networks, and wireless personal area networks (WPAN), using nanosecondwide pulses.
Electromagnetic Fields in Biological Systems
• The RF energies are transferred back and forth between the source (antenna) and
the body.
• The SAR level inside the body is influenced by direct interaction of the source with
the body.
• The electric field effect is weaker since dielectric permittivity of tissue is relatively
high.
• Inductive coupling of wireless antenna current–generated magnetic field dominates field coupling and power deposition or energy absorption.
• The SAR value varies with specific antenna configuration and the placement of
the antenna next to the head or body.
• Anatomy of the head and tissue inhomogeneity can influence the maximum value
and distribution of SAR in the head of a mobile telephone user.
• Integrated SAR (or average SAR) in the body is similar for both homogeneous and
inhomogeneous models.
• A large fraction (40%–50%) of the radiated RF power is absorbed by the human
body (including the head).
• The bulk of power deposition occurs on the side of the head nearest to the radiating structure of the cellular telephone.
• The SAR distribution follows an exponential trend away from the antenna side
and it is considerably lower elsewhere in the head of a cell phone user.
• Maximum SAR and its distribution in the head are functions of distance of the
radiating element from the skin surface and the current distribution on the
antenna.
• For a comparable level of electric field to be induced inside the body or a model by
an ELF magnetic field, the applied ELF electric field must be 120π times greater
than the electric field of a plane wave.
1.12 C oupling of Short and Ultra-Wideband
Pulses into the Human Body
The biological effects of electromagnetic pulses (EMPs) of varying durations have
long been investigated in research laboratories. Electromagnetic pulses with electric fields ranging from 20 to 500 kV/m or higher and with frequency spectra of
0–80 MHz are produced by nuclear EMP simulators. They are used to assess the
electromagnetic compatibility or immunity of electronic instruments and systems
under the conditions of a nuclear burst. However, it is only during recent years that
the benefit and capability of the large bandwidth provided by very short or ultrawideband (UWB) EMPs are being considered for imaging, sensing, and communication applications (Di Benedetto et al. 2006; Lin et al. 2008). Examples of applications
include biomedical imaging; vehicular radar; ground-penetrating radars (GPRs);
through-wall sensing; and communications systems such as handheld transceivers,
sensor networks, and wireless personal area networks (WPAN), using nanosecondwide pulses.