Development of measurement techniques for assessment of exposure to electromagnetic fields

Lauri Puranen

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

This thesis deals with measurement techniques used for assessment of the human exposure to electromagnetic fields. The measurements are in practice the only way to find out rapidly the exposure level in actual conditions. In addition, exposure setups and exposure assessment methods used in the animal experiments to study the health effects of mobile phones are discussed. Measurements are needed for the validation of the results obtained from computations with numerical models of the exposure setups and animals. The objectives of the human exposure studies were to optimize the configuration of a radio-frequency electric and magnetic field probe and to develop a practical technique for the measurement of the peak power density of pulsed microwave radiation from radars. In addition, the objective was to develop measurement techniques of induced body currents and contact currents to complement the results obtained from field strength measurements when assessing exposure to a non-uniform near field. The objectives of the animal exposure study were to develop a space efficient setup for the exposure of a large number of free moving rats to mobile phone fields at 900 MHz and to assess the exposure of the rats in the setup. A symmetrical configuration of the electric and magnetic field probe proved to be optimal according to the calculations which were validated with the measurements carried out for a prototype of the probe.The probe consisted of a double number of field sensors which were needed for an isotropic response. By doubling of the number of the sensors, the electric centre point of the probe was more accurately determined, the isotropy and linearity were clearly improved and the effect of the electric field coupling to the magnetic field sensors was significantly reduced. The hand-held meter developed for the peak power density measurements of pulsed microwave radiation of radars proved to be usable and reliable in actual conditions. Induced body current and contact current measurements were shown to complement the field strength measurements when assessing exposure to a non-uniform near field. The current transformers proved to be more usable and reliable than the parallel plate meters. The weighted peak method was successfully applied for the first time for assessment of the exposure to a broadband low-frequency contact current and it gave more realistic results than the conventional multiple frequency method. The setup developed in the animal exposure study proved to be usable for the exposure of a large number of rats in a room with a small available floor area. The exposure of the rats was assessed with computations using the numerical models of the setup and the rats. The results obtained from the computations were validated with calorimetric measurements using rat phantoms.
Translated title of the contributionMittaustekniikoiden kehittäminen altistumisen määrittämiseksi sähkömagneettisille kentille
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Räisänen, Antti, Supervisor
  • Toivonen, Tommi, Advisor, External person
Publisher
Print ISBNs978-952-60-7238-8
Electronic ISBNs978-952-60-7237-1
Publication statusPublished - 2017
MoE publication typeG5 Doctoral dissertation (article)

Keywords

  • exposure to electromagnetic field
  • electric field strength
  • magnetic field strength
  • microwave pulse
  • induced body current
  • contact current
  • exposure setup for rats

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