System Design And Research On Microwave Radiation Theory With Low SAR

The wide applications of microwave technology has brought enormous conveniences in our daily lives,but these technologies can produce the adverse effects in environment or biology.With the rapid development of mobile communication,the public focus more attention on the biological effects of microwave.There are two main biological effects of exposure to microwave,microwave thermal effect and non-thermal effect.Because microwave thermal effect has been well proved when radiation dosage is over the safe dosage,ICNIRP published the guideline which presented the SAR thresholds to protect the public from thermal effects.Although the non-thermal effects on the long term exposure to microwave with low SAR are focused in academia,there still were some conflicting results among the scientific literatures.This is due to the lack of well-characterized exposure conditions,such as the electromagnetic field uniformity in experiments and the scientificness of microwave radiation dose analysis and controlling system.In order to provide the well-characterized exposure conditions including the field uniformity in the region of interest(ROI)and the scientificness of radiation dose analysis and controlling system,the microwave radiation theory with low SAR and the exposure system design have been performed in this study.Based on the research of field uniform analysis in the ROI and SAR analysis on animals exposed to microwave,the constraint condition and the critical condition on field uniformity in the ROI were derived,and a SAR analysis database of animal models with high resolution and a low SAR dose control algorithm has been studied and built.Then,a microwave exposure system automatically controlling the duration and illumination has been designed.1800 MHZ microwave exposure experiment with low SAR was carried out using this designed microwave radiation system.The experimental data were processed by the cosine analysis software designed by the author,and then the results indicated that 1800 MHZ microwave radiation with low SAR influence the biological circadian rhythm.This study established a critical condition on field uniformity in ROI and a low SAR dose control algorithm,which provided a feasible theory for building low SAR condition in the microwave biological non-thermal effect research.The main work and contributions of this project are as follows:For enhancing the field uniformity in the ROI,a field uniformity theory in ROI of the far field has been presented and the critical condition on field uniformity in ROI was derived based on the criteria of IEC61000-4-20:2010 and the aperture field method(AFM).(a)The field distribution in ROI is numerically analyzed with AFM and the field uniform is evaluated according to IEC61000-4-20:2010,which describes a test method to evaluate the field uniformity of a defined area in TEM waveguide.The efficiency is improved on designing the microwave exposure setup when the field uniformity in ROI is evaluated in the design phase.(b)A critical condition on field uniformity in ROI was derived based on the microwave field uniformity theory according to the criteria of IEC61000-4-20:2010,which provides a reference standard for designing microwave radiation experiment system.Furthermore,the field uniformity in the designed ROI of microwave exposure system have been tested and well envaluated accordting to IEC61000-4-20:2010.For enhancing the scientificness of microwave dose analysis and controlling system,a method on analyzing SAR by animal models with high resolution is presented and a low SAR dosage control algorithm has been derived based on the microwave field uniformity theory.A SAR analysis database on “animal model-radiation frequency-SAR” is established and a low SAR microwave radiation system is designed and built.(a)IT'TS animal models are presented to analyze the average whole body SAR and local SAR in tissues and organs,and the SAR database is designed about IT'TS animal model that are exposed to TEM with 1V/m electric field and specified working frequencies.(b)Based on high resolution animal models,the SAR,microwave radiation dosage to animals,can be actually analyzed by the SAR analysis database and a low SAR dosage control algorithm has been derived.(c)According to the field uniformity theory in ROI,a low SAR microwave exposure system is designed by the SAR analysis of high resolution animal models and the low SAR dosae control algorithm.This system,automatically controlling the microwave amplitude and output during the specified time period,can be applied in the microwave non-thermal effects research such as circadian rhythms effects of microwave exposure on biology.In order to evaluate the feasibility of the study on microwave non-thermal effect induced by low SAR microwave radiation with the designed exposure system,a biological experiment is performed to study the circadian rhythmicity of antioxidant markers in rats exposed to 1800 MHz microwave with low SAR.In the experiment the SAR is analyzed by FDTD based on animal models and the low SAR is designed by low SAR dosage control algorithm.The sampled biological data is analyzed by the cosine analysis software based WEB designed in this project.The experimental results revealed that adverse effects on circadian rhythmicity of animals exposed to 1800 MHz microwave with low SAR.