With the increasing demand of higher operating frequencies for electronic circuits, the printed circuit board designers face more electromagnetic radiation problems than ever. Some “rules-of-thumb” are employed to help the designers to reduce the radiation problems. The 20H rule is one of printed circuit design rules, which intends to minimize the electromagnetic radiation. This project focuses on analysis and simulation of 20H rule’s signal propagation mechanisms. The model used in the project is a 2D planar structure. The numerical electromagnetic method, Finite Difference Time Domain (FDTD) method, is used for the field computation and analysis. Simulation is based on various structures of model and different distributions of excitation sources. Analysis focuses on the signal propagation models. Field distributions and radiation patterns are visualized by mathematical software. Meanwhile, Poynting vectors are calculated to give quantitative expression. The simulation results indicate three factors, namely, operating frequency, size of PCB and separation distance that will affect the function of 20H rule. The effects of three factors are shown by comparison of specific cases in this thesis. / Singapore-MIT Alliance (SMA)

Open site measurement on the electromagnetic interference is the most direct and universally accepted standard approach for measuring radiated emissions from an equipment or the radiation susceptibility of a component or equipment. In general, if the NSA measurements we recorded at different frequencies do not exceed the ideal value +-4dB, we would regard this site as a normalized site, otherwise it is not a normalized site as long as there is one measurement exceeds the range. A one change point model had been used to fit observed measurements. For each set of observations as well as the corresponding ideal values, we have the estimated regression parameter for a one change point model. Our ideal is using the difference of regression parameters between ideal values and observations to assess whether a site is qualified for measuring EMI or not. The assessment tool for whether the testing site is normalized or not is referred to the confidence region for the regression model parameters. Finally, according to the data collected in this experiment, the estimated parameters obtained from the observations will be used to do further statistical analyses and comparing the qualities of the four different testing sites.

The shielding effectiveness (SE) of the novel multiwall carbon nanotube (MWCNT) plastic composites is studied for the purpose of the electromagnetic interference (EMI) protection and the electromagnetic susceptibility (EMS) improvement in the application of the optical transmitter and receiver modules. The experimental results showed that the liquid crystal polymer (LCP) based MWCNT composites can exhibit a high SE of 38 dB ~ 45 dB within the frequency range of 1 GHz ~ 3 GHz. The shielding capability was demonstrated by examining the electromagnetic susceptibility performance of the optical transmitter and receiver modules, which were packaged by the MWCNT-LCP composites. The EMS performance was evaluated by eye diagram and bit-error-rate test in a 2.5 Gbps lightwave transmission system. The results showed that the MWCNT-LCP composite packaged modules with more weight percentage of the MWCNTs can exhibit a higher SE, and hence showed effective EMS performance, a better mask margin, and a lower power penalty. A novel polyimide (PI) plastic consisting of finely ionic liquid (IL) dispersed MWCNTs was also demonstrated to have high SE under a lower MWCNT loading. The experimental results showed that the IL dispersed MWCNT-PI composite can exhibit a high SE of 40 dB ~ 46 dB within the frequency range of 1 GHz ~ 3 GHz. By comparison, the composite fabricated by non-dispersed process required a higher loading of MWCNTs than the dispersed one. To understand the detailed intermolecular forces among MWCNTs, the dispersion mechanism of the MWCNTs is studied qualitatively. The aggregation of MWCNTs is from van der Waals forces among MWCNTs, and it can be dispersed by using IL dispersant. This is due to the predominant cation-

A clock driver that works on the principle of charging and discharging the clock network in a VLSI circuit in two steps is investigated in a few different configurations. The aim of the design is twofold: to reduce the power consumption to reduce the third harmonic of the clock signal, and thereby the EMI (electromagnetic interference) emitted by the clock network. The first should be possible to accomplish as the clock interconnect network gets charged by half the voltage during each rising transition, and the second should be possible to accomplish by carefully time the rising and falling transitions, so that the third Fourier coefficient of the resulting wave form cancels. The drivers are loaded by eight 16-bit adders. The drivers’ power consumption, and the spectrum of the output signal, are investigated under varying clock frequencies, power supply voltage, and driver architecture. The results are compared to a conventional square wave clock. The results are that while the third harmonics of the resulting output sees an improvement in all the investigated cases over the square wave clock, the power savings are, for higher clock frequencies, more than completely canceled by the extra power needed in the logic stage which controls these drivers. On the other hand, the power consumption of the new driver appears to drop below that of the conventional driver when the clock frequency drops below approximately 100MHz. A few suggestions for further investigations of new designs and clock wave forms are given.

Electromagnetic Interference (EMI) problems in switching power supplies have been traditionally treated with cut-and-try approaches. In recent years, advancement has been made to better understand the problems and minimize the cut-and-try portion of the design process. However, there are still phenomena difficult to explain in many practical design situations. Often, the problems may be solved by luck but many puzzles remain unsolved. If not fully understood, these puzzles are very likely to come back to haunt the designers. According to the conventional theory, there are two modes of noise: the Differential-Mode (DM) noise and the Common-Mode (CM) noise. Recently, a new noise-coupling mode called Non-Intrinsic Differential-Mode (NIDM) noise was uncovered accidentally in the process of explaining certain EMI filter action [1]. This phenomenon has never been thoroughly studied. The focus of the present thesis is to investigate the NIDM phenomenon and its implications to practical EMI filter design issues. The generation mechanism and basic characteristics of this phenomenon will be briefly reviewed, which is crucial to the understanding of the remaining parts of the research. Two essential diagnostic tools are introduced. One is the DM/CM noise separator and the other is the zero-span mode operation of a spectrum analyzer. The results of the investigation will be presented. The results will be presented using practical examples, which tie the phenomenon to filter design issues. In some examples, explanations are given to dispel the puzzles commonly encountered in the practice. A filter design procedure is suggested for off-line power supplies. This procedure incorporates the NIDM phenomenon into an existing design procedure. Only first-order and second-order filter topologies are included in the discussion. / Master of Science

This thesis presents the conducted electro-magnetic interference (EMI) prediction results for a continuous conduction mode (CCM) power factor correction (PFC) converter as well as the theoretical analysis for the noise generation and propagation mechanisms. In this thesis, multiple modeling and characterization techniques in the medium and high frequency ranges are developed for the circuit components that are important contributors to the EMI noise, so that a detailed simulation circuit for EMI prediction can be constructed. The conducted EMI noise prediction from the simulation circuit closely matches the measurement results obtained by a spectrum analyzer. Simulation time step and noise separator selection are two important issues for the noise simulation and measurement. These two issues are addressed and the solutions are proposed. The conducted EMI generation and propagation mechanisms are analyzed in a systematic way. Two loop models are proposed to explain the EMI noise behavior. The effects of the PFC inductor, the parasitic capacitance between the device and the heatsink, the rising/falling time of the MOSFET VDS voltage, and the input wires are studied to verify the validity of the loop models. / Master of Science

With the advent of wide bandgap (WBG) semiconductor devices, the electromagnetic interference (EMI) emissions are more pronounced due to high slew rates in the form of high dv/dt and high di/dt at higher switching frequencies compared to the traditional silicon technology. To comply with the stringent conducted emission requirements, EMI filters are adopted to attenuate the high frequency common mode (CM) and differential mode (DM) noise through the propagation path. However, self and mutual parasitic components are known to degrade the EMI filter performance. While parasitic cancellation techniques have been discussed at length in prior literature, most of them have focused mainly on single phase applications. As such this work focuses on extending the preexisting concepts to three-phase systems. Novel component placement, winding strategy as well as shielding and grounding techniques were developed to desensitize the influence of the parasitic effects on a three-phase multi-stage filter. The effectiveness of the three-phase filter structure employing the proposed methodologies has been validated via noise measurements at the line impedance stabilization network (LISN) in a 15kW rated motor drive system. Consequently, general design guidelines have been formulated for filter topologies with different inductor and capacitor form-factors. / Master of Science / The adoption of wide bandgap (WBG) semiconductor devices, such as Silicon Carbide (SiC) or Gallium Nitride (GaN) transistors, improves the power density with higher slew rates and switching frequencies compared to the traditional Silicon technology. However, the high switching speeds and high frequencies have generated higher electromagnetic interference (EMI) noise in the surroundings. To comply with the conducted emission requirements at the grid terminal, EMI filter is mandatory to attenuate the high frequency EMI noise that flows into grid. However, near field and the effect of parasitic components are known to degrade the filter performance at the higher end of frequency spectrum where the limit lines are typically stringent. While parasitic cancellation techniques have been discussed at length in prior literature, most of them has focused mainly on single phase applications. Therefore, this thesis aims to extend the pre-existing concepts to compensate the mutual and self-parasitic coupling components in a three-phase multi-stage filter. In this regard, novel component placement, winding strategy as well as shielding and grounding techniques were developed to compensate for the parasitic effects in a three- phase multi-stage filter. The effectiveness of the three-phase filter structure employing the proposed methodologies has been validated in a 15kW rated motor drive system. Consequently, general design guidelines have been formulated for filter design with minimal parasitic effects.

As a kind of education strategy, English as a medium of instruction (EMI) has become increasingly widespread across the world in recent years. The increased adoption means that many students are performing study activities such as reading, writing, and giving presentations in English all while maintaining and using a native language in other situations. One area of interest within EMI research is how it may relate to academic writing, and here there are relatively few studies aiming to examine the interactions between EMI and writing among master’s students. This paper collected qualitative interview data from five EMI master’s students who were asked to describe how they go about writing academic texts, what experiences and opinions they have of multilingualism in their lives, as well as how they may utilise the languages available to them to assist in their writing through code-switching or translanguaging. A thematic analysis was conducted which generated ten themes within two overarching categories, language use and multilingualism and writing behaviours. Participants in the present study reported no code-switching behaviours at any point throughout their writing, contrasting with previous research in multilingual university settings. This may be due to constraints of the EMI environment, where all produced materials from students need to be in English, discouraging the use of multiple languages and leading to opinions of sticking to one language being easier. Future research could usefully examine language use within EMI educational contexts with a focus on how it facilitates or otherwise affects code-switching tendencies. / English as a medium of instruction (EMI) har blivit en allt vanligare strategi inom utbildning under senare år. Dess utökning medför att många studenter utför studieaktiviteter som skrivning, läsning och muntliga presentationer på engelska och samtidigt bibehåller och använder sig av ett modersmål inom andra sammanhang. Ett intresseområde inom EMI-forskning är hur det knyter an till akademiskt skrivande, där det finns relativt få studier som fokuserar på samspelet mellan EMI och skrivande hos mastersstudenter. Denna studie samlade in kvalitativa data från intervjuer med fem mastersstudenter inom EMI program. De beskrev hur de gick tillväga vid akademiskt skrivande, vad de har för erfarenheter av och åsikter om flerspråkighet samt hur de använder sina tillgängliga språk till hjälp vid skrivprocessen genom så kallat code-switching eller translanguaging. En tematisk analys utfördes vilket skapade tio teman inom två breda kategorier, nämligen språkbruk och flerspråkighet och skrivbeteenden. Deltagarna i denna studie rapporterade inte att de använde code-switching alls inom skrivprocessen, till skillnad från tidigare studier från flerspråkiga universitetssammanhang. Detta kan bero på begräsningar inom EMI-miljöer, där texter och presentationer från studenter måste vara på engelska, vilket kan hindra användningen av flera språk. Framtida forskning skulle användbart kunna utforska språkbruk hos EMI-studenter med fokus på hur utbildningen med fokus på hur det underlättar eller annars påverkar code-switching tendenser.

Power factor correction (PFC) converter is a species of switching mode power supply (SMPS) which is widely used in offline frond-end converter for the distributed power systems to reduce the grid harmonic distortion. With the fast development of information technology and multi-media systems, high frequency PFC power supplies for servers, desktops, laptops and flat-panel TVs, etc. are required for more efficient power delivery within limited spaces. Therefore the critical conduction mode (CRM) PFC converter has been becoming more and more popular for these information technology applications due to its advantages in inherent zero-voltage soft switching (ZVS) and negligible diode reverse recovery. With the emerging of the high voltage GaN devices, the goal of achieving soft switching for high frequency PFC converters is the top priority and the trend of adopting the CRM PFC converter is becoming clearer. However, there is the stringent electromagnetic interference (EMI) regulation worldwide. For the CRM PFC converter, there are several challenges on meeting the EMI standards. First, for the CRM PFC converter, the switching frequency is variable during the half line cycle and has very wide range dependent on the AC line RMS voltage and the load, which makes it unlike the traditional constant-frequency PFC converter and therefore the knowledge and experience of the EMI characteristics for the traditional constant-frequency PFC converter cannot be directly applied to the CRM PFC converter. Second, for the CRM PFC converter, the switching frequency is also dependent on the inductance of the boost inductor. It means the EMI spectrum of the CRM PFC converter is tightly related the boost inductor selection during the design of the PFC power stage. Therefore, unlike the traditional constant-frequency PFC converter, the selection of the boost inductor is also part of the EMI filter design process and EMI filter optimization should begin at the same time when the power stage design starts. Third, since the EMI filter optimization needs to begin before the proto-type of the CRM PFC converter is completed, the traditional EMI-measurement based EMI filter design will become much more complex and time-consuming if it is applied to the CRM PFC converter. Therefore, a new methodology must be developed to evaluate the EMI performance of the CRM PFC converter, help to simplify the process of the EMI filter design and achieve the EMI filter optimization. To overcome these challenges, a novel mathematical analysis method for variable frequency PFC converter is thus proposed in this dissertation. Based on the mathematical analysis, the quasi-peak EMI noise, which is specifically required in most EMI regulation standards, is investigated and accurately predicted for the first time. A complete approximate model is derived to predict the quasi-peak DM EMI noise for the CRM PFC converter. Experiments are carried out to verify the validity of the prediction. Based on the DM EMI noise prediction, worst case analysis is carried out and the worst DM EMI noise case for all the input line and load conditions can be found to avoid the overdesign of the EMI filter. Based on the discovered worst case, criteria to ease the DM EMI filter design procedure of the CRM boost PFC are given for different boost inductor selection. Optimized design procedure of the EMI filter for the front-end converter is then discussed. Experiments are carried out to verify the validity of the whole methodology. / Ph. D.

An innovative structure for thin-film band-pass filters was proposed and analyzed. This structure was employed in the design, fabrication, and development of 3D IPD diplexers on glass substrates with double-side metallization electrically connected by through-vias. Through modeling, design, fabrication and characterization of the WLAN 3D IPD glass diplexers, the proposed filter structure was shown to enable miniaturized and high-performance RF passives. Further, component-level shield structures were developed to provide electromagnetic interference isolation between thin-film passives that are placed less than 100 µm apart. Glass substrates were designed, fabricated and characterized to demonstrate the shield effectiveness of metallized trench and via-array-based shields. The integration of such shields in miniaturized WLAN RF modules enables up to 60dB EM isolation in the frequency range of 1- 20GHz. Advanced RF module technologies based on 3D IPAC concept were designed and demonstrated with ultra-thin low-loss organic and glass substrates, integrating the proposed WLAN actives with miniaturized diplexer and EM shields. Double-side integration of such high-performance components on ultra-thin glass substrates enables up to 8x volume miniaturization including more than 3x reduction in area. Thus, the advanced components demonstrated in this research, vis-a-vis miniaturized diplexers and component-level EMI shields; integrated with actives in ultra-thin glass substrates using the 3D IPAC concept, can enable highly-miniaturized smart systems with multiband wireless communication capabilities.