Some Studies on RF Measurement and Modeling for Assessment of Radiation Hazard

Abstract

Radio planning, coverage estimation and Optimization are always a challenge for a RF engineer. RF estimation is done using any three of the methods namely Empirical relation, Statistical and Computational methods. Empirical methods provides good accuracy but is limited to area specific and hence many models have been are designed for the purpose. Some of these include the HATA model, Okumara-Hata extended model, Ericsson model etc. Computational methods on the other hand provides almost real time accurate estimation but demand very high computation cost. Most popular methods include Finite Difference Time Domain method (FDTD), Finite element method (FEM), Method of Moments (MOM) and etc. RF estimation using computational methods have been limited to indoor application because of their high computational cost. However, with the increase use of RF hardware coupled with advances in computation hardware cost these have been somewhat possible and recent trends in research has shown more research in this area. This thesis focuses both the empirical study and on computational electrodynamics for RF estimation. In addition to that, the thesis also analyses the hazards of Non-ionizing radiation due to high power transmitting sources like Radars, RF communication equipments and etc. The hazard assessment has been carried out for electromagnetic hazards upon man and machines with comparison of field strength measurements against the theoretical and international standards.

FDTD is a promising area for wide area of application and is independent of frequency; since it is based on time-domain method. In the thesis FDTD based power estimation is carried out using images from satellite. These input images have been taken from Google Earth. Using the color of the demographic features in the image, material properties have been determined. FDTD algorithm has been used to update electric and magnetic field using the partial equations and power is obtained using poynting’s theorem. The output is plotted as color mapping of the satellite image of the region, showing areas with different levels of power levels. The process has been applied to three different cities of state of Odisha (India).

Besides that, RF measurement at a location housing high power transmitting RF sources have been analysed for hazard assessment. RF power at different locations has estimated taken to assess for any unwarranted radiation hazards like RF burns on human, pre-mature activation of RF sensitive devices like arms and ammunitions etc. Equivalent electric field strengths were obtained from the Measure RF power. Measurement was carried out at different locations to ascertain the RF signal power at different location in a range of 1Km to 10 Km It was observed that the values of the aggregated field strength at all measured locations were below the threshold values for any radiation hazard.

The thesis broadly provides; RF estimation using computations method of FDTD; RF measurement and assessment on man and machine due to high power radiation at site-specific location.