The overall aim of this thesis is to increase our knowledge of relevant exposure parameters when discussing possible health implication from exposure to radiofrequency electromagnetic fields (RF), especially effects that might occur at non-thermal levels. In this thesis an effort is made to broaden the exposure assessment and to take the exposure time into account and combine it with the Specific Absorption Rate (SAR) and the field parameters (electric and magnetic field strength) to approach a dose concept. In the first part of the thesis self-reported subjective symptoms among mobile phone users were studied. As a basis for this an epidemiological study among mobile phone users was completed with the main hypothesis that users of the digital transmission system GSM experience more symptoms than users of the older analogue NMT transmission system. The hypothesis was falsified, but an interesting side finding was that people with longer calling time per day experienced more symptoms than people with shorter calling time per day. The time-aspect (long duration phone call etc.) was also found to be relevant for the occurrence of symptoms in association with mobile phone use as well as duration of symptoms. The new suggested dosimetric quantity Specific Absorption per Day (SAD), in which both calling time per day as well as the measured SAR1g are included showed a stronger association to the prevalence of some of the symptoms, such as dizziness, discomfort and warmth behind the ear compared to both CT and SAR1g alone. In the second part whole body exposure conditions were considered. Methods to measure the induced current were examined in an experimental study, where different techniques were compared in different grounding conditions. The results were used in a study of operators of RF plastic sealers (RF operators) where the health status as well as the exposure were studied. The results showed that RF operators are a highly exposed group, which was confirmed by the fact that 16 out of 46 measured work places exceeded the ICNIRP guidelines. Headaches were found to be associated with the mean value of the time integrated E-field during a weld (E-weld) and the warmth sensations in the hands (warm hands) with the time integrated E-field exposure during one day (E-day). The general findings in this thesis indicated that time should be included in the exposure assessment when studying non-thermal effects such as subjective symptoms in connection with RF exposure. The thesis proposes two different methods for doing this, namely timeintegrated exposure [V/m x t and A/m x t] and dose [J/kg].

<p>The overall aim of this thesis is to increase our knowledge of relevant exposure parameters when discussing possible health implication from exposure to radiofrequency electromagnetic fields (RF), especially effects that might occur at non-thermal levels.</p><p>In this thesis an effort is made to broaden the exposure assessment and to take the exposure time into account and combine it with the Specific Absorption Rate (SAR) and the field parameters (electric and magnetic field strength) to approach a dose concept.</p><p>In the first part of the thesis self-reported subjective symptoms among mobile phone users were studied. As a basis for this an epidemiological study among mobile phone users was completed with the main hypothesis that users of the digital transmission system GSM experience more symptoms than users of the older analogue NMT transmission system.</p><p>The hypothesis was falsified, but an interesting side finding was that people with longer calling time per day experienced more symptoms than people with shorter calling time per day. The time-aspect (long duration phone call etc.) was also found to be relevant for the occurrence of symptoms in association with mobile phone use as well as duration of symptoms. The new suggested dosimetric quantity Specific Absorption per Day (SAD), in which both calling time per day as well as the measured SAR1g are included showed a stronger association to the prevalence of some of the symptoms, such as dizziness, discomfort and warmth behind the ear compared to both CT and SAR1g alone.</p><p>In the second part whole body exposure conditions were considered. Methods to measure the induced current were examined in an experimental study, where different techniques were compared in different grounding conditions. The results were used in a study of operators of RF plastic sealers (RF operators) where the health status as well as the exposure were studied. The results showed that RF operators are a highly exposed group, which was confirmed by the fact that 16 out of 46 measured work places exceeded the ICNIRP guidelines. Headaches were found to be associated with the mean value of the time integrated E-field during a weld (E-weld) and the warmth sensations in the hands (warm hands) with the time integrated E-field exposure during one day (E-day).</p><p>The general findings in this thesis indicated that time should be included in the exposure assessment when studying non-thermal effects such as subjective symptoms in connection with RF exposure. The thesis proposes two different methods for doing this, namely timeintegrated exposure [V/m x t and A/m x t] and dose [J/kg]. </p>

Chromophoric Dissolved Organic Matter (CDOM) is a substance produced by the planktonic community that naturally blocks biologically damaging, ultraviolet radiation (UV; wavelengths = 280 to 400 nm). While a variety of planktonic species produce CDOM, investigations into the quality and quantity of their CDOM production are few. The purpose of this study was to investigate the properties of CDOM produced by phytoplankton versus zooplankton. Typically, UV radiation breaks down CDOM. However, marine organisms sometimes produce CDOM that, when exposed to sunlight, increases its absorbance of UV radiation. The reasons for this anomaly and the source of this unusual CDOM are unclear. To test for distinctions among sources, filtered water samples from cultures of two marine phytoplankton, Gymnodinium sp. and Dunaliella sp., and a marine copepod, Tigriopus californicus were exposed to sunlight for intervals of 0, 0.5, 1, 2, and 4 hours. The maximal UVB radiation (wavelengths; λ = 280 to 320 nm) was 0.1699 J cm-2. Before and after sunlight exposures, CDOM sources were assessed by comparing absorbance spectra from 184 to 730 nm with detailed comparisons at wavelengths of 254, 305, 320, and 350 nm. Results are expressed as "absorption", which is the raw absorbance converted to the natural log. Before exposure to sunlight, CDOM from algal species had 5- to 8-times higher average absorption values across UV wavelengths than CDOM produced by Tigriopus. CDOM samples produced by phytoplankton were more susceptible to photochemical change than CDOM from Tigriopus. In response to sunlight, CDOM from Gymnodinium varied greatly, increasing in UV absorption in 2 out of 5 replicates but decreasing in absorption in the other replicates. In contrast, peak absorption at λ = 260 nm of CDOM from Dunaliella decreased directionally by an average of 76% in absorption and 75% in specific absorption, and this decrease in absorption was significant (p = 0.03). CDOM from Tigriopus significantly decreased in both absorption (all UV wavelengths, p < 0.01) and "specific absorption", which is absorption standardized per mg of dissolved organic carbon (λ = 320 nm; p < 0.03), but the magnitude of change was only 17%. Thus, photochemical responses of CDOM from the three planktonic sources demonstrated more, consistently less, and unchanged UV absorption. Phytoplankton biomass, which is greater than that of copepods at the next trophic level, likely produce more CDOM but because of greater variability in CDOM absorbance of UV both within and between algal sources, copepods may offer a more stable source of UV protection depending on sunlight exposure and their relative abundance. Definitive conclusions depend on future laboratory studies expanded to more planktonic organisms as well as in situ studies during oceanographic cruises to test the relative contributions of planktonic species.

In this thesis, intelligent metamaterial was designed to reduce the peak specific absorption rate (SAR) value. Intelligent metamaterial means that when the antenna is far away from a human head, the metamaterial behaves like air and it does not affect the antenna performance; when the antenna is close to a human head, however, the metamaterial acts like a single negative (SNG) material. We designed two kinds of intelligent metamaterial structures. One makes use of impedance mismatching, and the other makes use of the frequency band shift property to reduce the peak SAR value at the operating frequency. The former structure is broadband, and it can reduce the peak SAR value by 56.7%. The latter structure has a much smaller size compared to the former one, and it is suitable for cellular phone applications. The peak SAR value can be reduced by 40% using the latter structure. The proposed two kinds of the intelligent metamaterial structures do not affect the antenna performance. Finally, the intelligent metamaterial has been applied to a cellular phone. The dimension of the intelligent metamaterial is only 40 mm ¡Ñ 20 mm ¡Ñ 0.8 mm. The intelligent metamaterial does not affect the antenna performance when the antenna is far away from a human head. When the antenna is close to a human head, the peak SAR is reduced by 41.7%.

In recent years, the rapid development of wireless communications has resulted in much better quality of life due to easiness and multitudes in communications. The most representative products are the mobile phones. The product is so popular that in developed countries nearly everyone owns a mobile phone; that applies not only to adults, but also young students. In view of this wide spreading phenomenon, the mobile phone industry has inescapable health related responsibilities for its users, especially for the younger ones. While enjoying the great convenience of the product, the users are advised to understand the possible health related effects caused by electromagnetic radiation. One of the very important considerations is Specific Absorption Rate (SAR), in which absorption of electromagnetic energy by a medium (for example, a human head) is measured. Before a mobile phone is brought into the market, it is important to understand how the SAR values can be affected by the metallic accessories around the human head. This thesis uses software package, SEMCAD, to analyze the metallic accessories on the human head which might influence the SAR value. We would discuss in this thesis three object, eyeglasses, earrings and rings which could affect the maximum SAR value in the human head. For eyeglasses and earring, we would suggest why these metallic accessories at different position could cause different SAR value to suggest people which gesture should be avoided while using the cell phone. For ring, this thesis would use the shape of the ring and place it at special position to decrease the maximum SAR value in the human head to reduce the possible harm from the electromagnetic radiation of mobile phone and ensure the safety while using a cell phone.

In this thesis, two novel broadband slot mobile phone antenna designs respectively for penta-band WWAN operation and eight-band LTE/WWAN operation are presented. The antennas are suitable to be mounted near the bottom edge of the system ground plane of the mobile phone. Good radiation characteristics for the antennas are obtained, and the two antennas respectively occupy a small printed area of 50 ¡Ñ 4 mm2 and 53 ¡Ñ 4 mm2. The first design uses a C-shaped strip connected to the bottom edge of the system ground plane to make the structure of the system ground plane close to a symmetric shorted dipole antenna. This makes it promising to excite a chassis mode to enhance the operating bandwidth of the antenna. The second one uses a microstrip feedline having a chip-inductor-loaded branch. The novel microstrip feedline can lead to more uniform distribution of the electric fields excited in the slot such that enhanced bandwidth of the antenna¡¦s lower band is obtained. Further, since the chip inductor performs like a low-pass filter, the original bandwidth of the antenna¡¦s upper band is not affected. Additionaly, the impedance matching of the lower frequencies of the upper band can be improved, which enhances the upper-band bandwidth of the antenna. Effects of the user¡¦s head and hand on the proposed antenna are also studied, and the simulated SAR and HAC issues are also analyzed in this thesis.

In recent years, the wireless communication operators use more and more systems based on the transmission and reception of EM waves. As a result, more and more base stations are being installed on the rooftop of existing buildings in densely populated areas. The prevailing of wireless communications has prompted the public¡¦s concern of the health issue. To date, the most prominent and scientifically verifiable biological effect of EM waves is the heating effect. In order to maintain the users¡¦ health from the over-heating due to excessive use, analysis of the temperature distribution inside the human body is also very critical as well as the SAR guidelines. The purpose of this thesis is to investigate the SAR values and temperature distribution inside the human head, under the EM exposure of mobile communication base station and handset based on the use of finite-difference time-domain (FDTD) method. In general, we assumed that the far-field exposure of base station are uniform plane-wave exposures. The total-field / scattered-field (TF/SF) formulation implements a compact uniform plane-wave source permitting FDTD simulations to accurately predict the SAR distribution in the human head due to uniform plane-wave exposures. Furthermore, this thesis investigates the effects of the rectangular frames of the metallic spectacles at 900MHz and 1.8 GHz for the uniform plane wave.

All wireless devices expose users to some level of electromagnetic radiation during operation. In many countries, exposure levels are strictly regulated to ensure the safety of consumers. Previous research demonstrates that incorporating exposure constraints into transmit signal design leads to substantial capacity gains over traditional power back-off techniques. This is especially vital for millimeter wave systems, which require large array gains to combat high path losses and are more susceptible to a decrease in transmit power. In this work, we present exposure modeling procedures and exposure-aware transmission schemes for millimeter wave systems. We first develop methods to approximate the characteristic matrix of a quadratic model for two exposure measures in the millimeter wave band: incident power density and surface specific absorption rate (SAR). The proposed models can be calculated with a small number of parameters and can be altered to account for changes in the exposure scenario. Software simulations with half-wave dipole antennas corroborate the accuracy of the exposure models in the millimeter wave band. We then exploit the ability of the model to calculate exposure at any point surrounding the device to develop efficient exposure-aware signaling strategies. Finally, we propose a low-complexity perturbation approach to obtain exposure-compliant beamforming vectors. Analytical and numerical results demonstrate that the proposed exposure-aware signaling techniques outperform power reduction approaches.

In this dissertation a study of enhanced hyperthermia for cancer treatment through the use of magnetic nanoparticles is presented. Hyperthermia has been in use for many years, as a potential alternative method in cancer treatment, and high frequency microwave radiation has been used successfully to raise the tumor temperature to around 42°C in superficial tumors without causing damage to surrounding healthy tissues. Magnetic fluid hyperthermia involves the use of magnetic nanoparticles injected into the tumor before exposure to microwave radiation. The magnetic energy in the nanoparticles is converted into heat allowing for a more rapid rise of temperature in the tumor to the desired level. In addition, the nanoparticles allow the electromagnetic absorption to be focused in the tumor and can be used to treat deep tumors in organs, such as the liver. Iron oxide magnetic nanoparticles were considered for this study as they are non-toxic and bio-compatible. For the case of breast cancer, the values for the temperature and specific absorption rate (SAR) in the tumor and in the healthy tissue were obtained through simulations and validated by measurement done on phantom models. Various characteristics of the nanoparticles such as radius, magnetic susceptibility and concentration were considered. In order to take the effect of the blood flow, which causes cooling and helps maintain the body temperature, various blood perfusion rates for a tumor in the liver were studied. A human male model in SEMCAD X, in which blood flow can be adjusted, was used for simulations. The tumor was injected with the nanoparticles and the change in temperature upon exposure to electromagnetic radiation was observed. The simulated results were compared with measured results on a liver phantom model in which saline solution was used to model blood flow. There was good agreement between the measured and simulated results.

No / A procedure to reduce the effect of the mobile antenna on the handset by using balanced antennas has been investigated. Use of this type of antenna may degrade the antenna performance, such as bandwidth and gain, although it can cause less effect on the body to which they are adjacent. If the antennas are well designed, the maximum specific absorption rate (SAR) values are likely to be reduced when placed next to the head, since the coupling of such antennas to the body of the handset is very weak. A study on balanced and unbalanced antennas for mobile handsets next to the human head is presented, using a hybrid electromagnetics method for the analysis. The method uses the hybridisation technique between the frequency-domain method of moments (MoM) and the finite-difference time-domain method (FDTD). The antenna was modelled using MoM whereas the head tissues were modelled using FDTD. Two antennas were designed and investigated with respect to the SAR and radiation performance for two different antenna positions on the top edge of a mobile handset. Radiation patterns are presented and compared, with and without the head, and the maximum SAR values and field distributions inside the head are discussed. The balanced antenna shows good improvements with respect to the unbalanced antenna in terms of the SAR values and variations of the input impedances.