Electromagnetic interference

This study is performed as a partial aid to a larger study that aims to determine if
electromagnetic fields produced by underwater power cables have any effect on marine
species. In this study, a new numerical method for calculating magnetic fields around
subsea power cables is presented and tested. The numerical method is derived from
electromagnetic theory, and the program, Matlab, is implemented in order to run the
simulations. The Matlab code is validated by performing a series of tests in which the
theoretical code is compared with other previously validated magnetic field solvers. Three
main tests are carried out; two of these tests are physical and involve the use of a
magnetometer, and the third is numerical and compares the code with another numerical
model known as Ansys. The data produced by the Matlab code remains consistent with
the measured values from both the magnetometer and the Ansys program; thus, the code is
considered valid. The validated Matlab code can then be implemented into other parts of
the study in order to plot the magnetic field around a specific power cable.

This thesis addresses pertinent studies concerning the use of electromagnetic composite media as EMI shielding materials. Specifically biphasic composites constituted by conducting and/or lossy inclusions dispersed in a dielectric host are considered. The effects of conductivity and/or dielectric loss, shape, size and volume fraction of the included component in deciding the shielding effectiveness of the composite material are ascertained over radio frequency spectrum. Theoretical studies in modeling the effective complex permittivity of the test composite are presented in the classical and state-of-the-art perspectives and hence the shielding effectiveness of the test composite is elucidated. The theoretical considerations also refer to two types of inclusions namely, conducting particulates (metallic particles, fibers and flakes), and lossy nonmetallic inclusions. In the first case the host-inclusions system refers to polemically opposite constituents and in the later case, it is simply a dielectric-dielectric mixture. Experimental studies to evaluate the shielding effectiveness of a set of test composite are presented. Relevant descriptions include details on the test composites synthesized, experimental arrangement and the test procedure followed. Particulars on test materials constituted by a host ceramic medium (such as TiO2) with conducting inclusions such as iron particles, copper rods and aluminum flakes are presented. Measured results on the shielding effectiveness of these materials over the frequency range (200 to 1500 MHz) are listed and compared with theoretical results. Conclusions and discussions as regard to pertinent applications of such materials are presented.

This study presents computer simulations directed to address the performance of a baseband Bluetooth system. These simulations help to understand the performance impairments experienced by the Bluetooth systems in the presence of external electromagnetic interference (EMI) and interference that arises from piconet neighbors. The simulation results show that the effect of small scale fading is an important factor that decides the performance of a Bluetooth system. Additionally, it is shown that the interference from piconet neighbors or the interference that stems from devices belonging to the same piconet can be reduced by using frequency-hoping and time synchronization improvised within the same piconets. The test simulations were performed using MatlabRTM and SimulinkRTM tools.

What have been envisaged and focused in the research as deliberated in this dissertation, refer to certain state-of-the-art perspectives of modern wireless telecommunications. Specifically, the objectives and scope of the research efforts carried out include systematic analyses of two major wireless technologies, namely, the Bluetooth(TM) and the CDPD system. The relevant tasks undertaken refer to analytical modeling, experimental studies and simulations pertinent to the performance considerations of the test systems subjected to EMI/RFI influences. The following can be enumerated as the specific research endeavors pursued and completed: (1) Identification of performance implications in the Bluetooth(TM) and CDPD wireless transmissions subjected to EMI/RFI ambients. (2) A comprehensive presentation on the system description, performance requirements, protocol issues and operational environments of the two wireless technologies under study. (3) Development of analytically tractable models, which describe the extent of EMI/RFI on the Bluetooth(TM) operations and provide expressions to compute the transmission impairments involved in terms of the associated packet losses. (4) Modeling of CDPD performance and deducing the statistics of data packets seizing the free AMPS channels. The associated results offer compatible simulations to deduce the data packet blocking probability. The enhancement of such blocking caused by any impulse-like noise invading the system is also modeled. (5) Proposals for methods towards EMI solutions through adopting novel shielding in the wireless systems. The aforesaid efforts are comprehensively addressed supplemented with appropriate background details and literature survey. In conclusion, the scope of the present study is discussed and possible open-questions for future study are identified.

A formulation with its computer code based on the method of moments for thin wire structures is used for modeling the radiated fields emanated from a multilayer PCB. The moment method modeling technique proves to be a valuable tool for EMI prediction in a PCB at radio frequencies as well as useful design technique for obtaining the PCB layout which produces the least amount of radiation. A new modeling of the current distribution which includes the effect of microstrip open-end and bend discontinuities is used. The new modeling increases the accuracy of the prediction model for calculating the radiated EMI. The applicability of the moment method technique for studying the current distribution of wide microstrip is shown by modeling the existence of longitudinal and transverse currents at bend discontinuities.