Dielectric resonator antennas(DRAs) offer some attractive characteristics over conventional microstrip antennas, such as small size, low profile, light weight, ease of excitation, and high radiation efficiency at higher frequency bands. Since DRAs attract more and more attention, theoretical analysis have been insufficient to simulate various configurations of dielectric resonator antennas. Therefore some researchers introduce numerical methods to analyze DRAs, such as Finite Difference Time Domain (FDTD) method, Method of Moment (MoM), Finite Element Method (FEM). In this author, we apply two kinds of methods, including FDTD and MoM, to analysis DRA and compare the results applied these two methods. Then we simulate various configurations of dielectric resonator antennas using FDTD method. About designing the DRA construction, in this author we applied an equivalent approach to solve approximate dimensions of DRAs, and then we obtain accurate dimensions using FDTD method. In this author¡Aa DRA work at 5.8GHz have been proposed, then we using a L-shaped patch to increase impedance bandwidth. Above all, we hope to built a fast and accurate procedure to solve the resonant frequency, bandwidth, and far field pattern of DRAs. And to supply the engineer to reduce time consume in design DRAs.

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.

Genetic algorithms (GAs) are global optimization methods that can be applied to almost all problems, requiring only proper fitness function to evaluate. However, one problem of general GA is slow convergence. An improved GA is presented to speed up the efficiency of searching for global optimum in this author. The concept of this proposed method uses a few cost to obtain better individuals in initial population, and the evolution of GA is divided into two-stage with the concept of the genetic evolution process, which uses to improve efficiency. An improved GA with finite-difference time-domain (FDTD) will be applied to optimize mushroom-type EBG structures, which can obtain a wide range stop-band by adjusting the position of via with different patch size cascaded without changing via size, then the simulation and measurement results are also compared. In addition, the novel steps will be presented to design broadband mushroom-type EBG structures with smaller size systematically.

The Finite-Difference Time-Domain method ( FDTD ) is a numerical method introduced by K. S. Yee in 1966. However , it needs so much time to simulate circuits by applying the FDTD method and some extensional methods for simulating circuits are still incomplete . Therefore, the author combine the FDTD method with the data extrapolation method to improve the simulation effect. When applying the FDTD method to simulate circuits, it needs a large number of time steps; furthermore, if the structure we simulated is complicated, the simulation time will be so much longer that the efficiency of simulation will be bad as well. The author decrease the number of time steps of the FDTD method, and then extrapolate the time-domain data to reconstruct the complete frequency response, therefore, we can save the simulation time as well because the number of the time steps of the FDTD method decreased. Furthermore, in the thesis, we also introduce a new FDTD method combined with the S-parameter Matrix, called ¡§S-parameter Matrix method¡¨. People can simulate circuits without deriving the equivalent circuit by applying the S-parameter Matrix method. One only have to obtain the S-parameter Matrix by measurement, data sheet, calculation, etc, and then we translate it to time domain data by the IFT technique to apply the FDTD calculation , this way, we avoid the difficulty of deriving the equivalent circuit of general microwave circuits. However, the S-parameter data we can obtain are often limited in a finite bandwidth, we make it to be extrapolated to obtain the complete time-domain response, and this way, the S-parameter Matrix method can by apply to simulate circuits.

Many electromagnetic problems can be simulated by FDTD method. Mainly, we use orthogonal cartesian coordinate in normal situations when we deal with the electromagnetic problems. Because in most situations, the structures simulated are simply rectangular. But sometimes we may need to simulate the structures which are not rectangular like the sharps of arc and circle. For this kind of problems, the tranditional FDTD method no longer works, so the tranditional FDTD method must be modified to fit the simulation of irregular structures. Besides the FDTD method we mention above, we even combine it with non-uniform grid method in more applications. And the time to apply it is when the object simulated both has the rectangular and curved structures in the same time like the microstrip fed by the coaxial cable. The situations like that would be a good time to apply it.

Transient current surges resulted from the simultaneous switching of output buffers in the high-speed digital circuits can induce significant ground bounce noise (GBN) on the chip, package, and printed circuit board (PCB). The GBN not only causes the signal integrity (SI) problems, such as glitches or timing push-out of signal traces, but also increases the electromagnetic interference (EMI) in the high-speed digital circuits. With the design trends of digital circuits toward higher speed, low voltage level, smaller volume, the impact of GBN has become one of the most important issues that determine the performance of electronic products. Adding decoupling capacitors between the power and ground planes is a typical way to suppress the GBN. However, they are not effective at the frequencies higher than 600MHz due to their inherent lead inductance. Recently, a new idea for eliminating the GBN is proposed by designing electromagnetic bandgap (EBG) structure with high impedance surface (HIS) on the ground or power plane. Several new EBG power/ground plane designs have been proposed to broaden the stopband bandwidth for suppressing the GBN. However there are some drawbacks, such as high cost, large area occupation and complicated fabrication process. In this paper, we propose a novel Hybrid EBG power planes for PCB or package to suppress the GBN. Its extinctive behavior of broadband suppression of GBN (over 10GHz) is demonstrated experientially and numerically. Finally, we combine the periodic high-low dielectric material with the EBG power plane to control the position and bandwidth of stopband.

The disadvantage of FDTD method is that it needs a long simulation time, and it is difficult to simulate a complex circuit. The methods to improve the efficiency in FDTD simulation are increase in width of time step, enlargement in space grid and extrapolation of late time records. In this paper, we predict the late time record in FDTD simulation by applying Prony¡¦s method, and save the computation time of FDTD simulation. The cost of computation time of Prony¡¦s method is low, and it has a good result that applying Prony¡¦s method at predicting a waveform which resonates with period. In this paper, we try to make a rule for finding training start point and width of training period in Prony¡¦s method. The result of prediction with a short period of time records under the rule is accurate and reliable

A full wave finite-difference time-domain method (FDTD) combined with thin-wire and thin-slot algorithms to analyze a metamaterial fabricated with periodic mushroom structures, is proposed in this dissertation. This proposed method is suitable for analyzing problems involving large structures with fine structural details. A periodic analysis for mushroom structures is presented. Only a single unit mushroom cell is required to present the phenomena of infinite periodicity with the help of periodic boundary conditions (PBCs). The composite right-/left-handed (CRLH) transmission line (TL) approach is introduced and used to approximate CRLH metamaterial through lumped L and C. Finally, several CRLH metamaterial mushroom-based structures are investigated. A 19 by 8 flat microwave lens and a parabolic microwave lens structure composed of 410 unit mushroom cells are investigated. These structures demonstrate negative refractive index (NRI) characteristics while operate in the left-hand (LH) region. The simulation and measurement results of one- and two-dimensional CRLH mushroom-based structures are compared.

The trends of present design in electronic systems are towards high speed, small size, and lower voltage levels. The noise immunity of high speed digital circuit decreases. ESD problem becomes more and more important for electric products because of the triboelectricity caused by human body with synthetic material. In this thesis we introduce the phenomenon in real life ESD caused by a charged human body source. Then we provide a good measurement method of ESD which enhances the repetition that gives a reliable and accurate result. Finally we try to build the numerical model for the air and contact discharge simulation by FDTD to provide a good measurement validation.

Because the metal enclosure with apertures is the structure of the cavity form, FDTD method belonging to full-wave analytical algorithm isn¡¦t efficient for analyzing such case. Thereby the ETL method belonging to analytical formulation provides another way to analyze it. Although the structure which it can apply to isn¡¦t as complex as that in full-wave analytical algorithm, the computing time is shorter than FDTD. In contrast, the method can¡¦t get good agreement. Thus two improved ways are introduced in this paper. One is to make the suitable structure wider and the other is to consider the higher mode original ETL method isn¡¦t included to improve the accuracy. Further these two ways make the suitable range of the method wider and the method has good practicability.