Tae Hong Kim

Size reduction of electromagnetic bandgap (EBG) structures with new geometries and materials

Size reduction of an electromagnetic bandgap (EBG) structure with large patches and small branches that connect adjacent patches for a power/ground plane pair is studied. To shrink the dimensions with a high isolation at the frequency of interest, this paper provides two approaches. One is a geometric approach which is to place two narrow slits on each patch. The increase of branch inductance with the long slit successfully decreases the on-set frequency of the stopband without increasing the patch size. The other approach is to use high-K material for a thin dielectric layer. In this case, the size reduction can be predicted according to a scaling law. These approaches are applied together to realize an EBG structure with the entire size of less than 20 mm on a side. It covers the GSM band with sufficient isolation. Through this study, the dispersion-diagram analysis is used to predict the stopband characteristics

Stopband Analysis Using Dispersion Diagram for Two-Dimensional Electromagnetic Bandgap Structures in Printed Circuit Boards

Electromagnetic bandgap (EBG) structures that provide an excellent isolation within the stopband are extremely effective in suppressing propagation of simultaneous switching noise on parallel power planes. However, a scattering parameter measurement and full-wave electromagnetic simulation for their entire structure are costly and time consuming. This letter presents a two-dimensional dispersion-diagram analysis based on a unit-cell network of EBG structures by extending a well-known dispersion-diagram analysis of one-dimensional infinite periodic structures. The approach is extremely effective in computing stopband frequencies and provides the stopbands with good agreement to the measured results

Air-Gap Transmission Lines on Organic Substrates for Low-Loss Interconnects

The fabrication of low-loss transmission line structures with an air dielectric layer is described. The channels are characterized at low frequency (10 and 100 kHz) using capacitance and loss tangent and at high frequency (500 MHz to 10 GHz) using -parameter measurements. The incorporation of an air gap resulted in structures with effective dielectric constants between 1.5-1.8 and significantly lower loss tangents. The fabrication technique could be used to create more complicated air gap transmission line structures for use in monolithic microwave integrated circuits.

Stopband prediction with dispersion diagram for electromagnetic bandgap structures in printed circuit boards

Electromagnetic bandgap (EBG) structures that prevent propagation of electromagnetic waves within a given frequency range are quite effective in suppressing simultaneous switching noise on parallel power planes. However, it is quite time consuming to compute the stopband frequencies of interest using full-wave electromagnetic simulation of the entire structure. In contrast, using dispersion-diagram analysis based on a unit- cell network of EBG structures is more efficient and less time consuming. This paper presents an approach for two-dimensional EBG structures by extending a well-known dispersion-diagram analysis of one-dimensional infinite periodic structures. The stopbands predicted with the proposed analysis were compared with good agreement to measured and simulated results. In addition, the concept was applied to test the stopband range of EBG structures formed on an actual printed circuit board with a test coupon of an EBG unit cell placed on the same board.

A novel synthesis method for designing electromagnetic band gap (EBG) structures in packaged mixed signal systems

Electromagnetic (EM) simulation of electromagnetic band gap (EBG) structures is computationally expensive when multiple iterations are required. For the first time, in this paper, a novel synthesis method for designing EBG structures has been proposed. The method consists of three major approaches: current path approximation method (CPA-method), border to border radius (B2BR), and power loss method (PLM). CPA-method is based on the current flow on a periodically patterned power/ground plane. CPA-method gives a final dimension of EBG structure for a desired stop band frequency. B2BR determines the maximum number of patches implementable within a given area. PLM calculates isolation level of an EBG structure based on the transmitted power. The proposed approaches have been combined together to synthesize an EBG structure for a given specification. The synthesized EBG structure with these approaches has been fabricated and verified with EM simulation and measurement. The EBG structure has shown excellent stop band and isolation level agreements with the desired specification

Electromagnetic Band Gap Synthesis Using Genetic Algorithms for Mixed Signal Applications

A novel electromagnetic band gap (EBG) synthesis method for mixed signal applications is presented. In this method, a genetic algorithm (GA) is utilized as a solution-searching technique. One of the main advantages of the proposed method is an automated design procedure for EBG structures that meet given design specifications. For this purpose, the GA method is combined with multilayer finite-difference method (M-FDM) and dispersion diagram (DD) method. The M-FDM is a circuit-based simulator for computing the Z-parameters of planar structures, while the DD method is a plot of the propagation constant versus frequency. The EBG synthesis method introduced in this paper consists of three main parts namely: 1) GA, which generates populations of EBG structures and evaluates fitness functions using band gap response results from DD; 2) M-FDM, which analyzes the EBG structures generated by the GA and links the analysis results to DD; 3) DD, which calculates band gap frequencies using the EBG structure analysis results from the M-FDM and links the calculated stop band frequencies to the GA for fitness checks. For the verification of the suggested method, EBG structures having various specifications have been designed using the EBG synthesizer tool described in this paper. The designed EBG structures have been modeled and simulated using M-FDM. The EBG structures have also been fabricated and measured in the frequency-domain. The corresponding frequency-domain simulations and measurements have exhibited band gaps as per the design specifications used to synthesize the EBG structures.

Miniaturization of Electromagnetic Bandgap (EBG) Structures with High-Permeability Magnetic Metal Sheet

Electromagnetic bandgap (EBG) structures in a pair of parallel planes are quite effective for suppressing simultaneous switching noise, but they are too large to be applied to compact electronic devices. To miniaturize the EBG structures, we investigated an approach to interpose a high-permeability magnetic metal sheet between the parallel planes. The experimental results show that high permeability of the sheet shifts the stopband towards lower frequencies. This suggests that such sheets contribute to the miniaturization of the EBG structures. In addition, it is demonstrated that the imaginary part of the permeability can expand the stopband.

Printed monopole antennas with increased bandwidth and gain for wi-fi applications

In this paper, a method to enhance the performance of printed monopole antennas is presented. The proposed approach consists of placing a metal patch next to the antenna in order to direct the fields in one direction by using the reflection from the metal patch. This topology provides compact antenna solutions with broader bandwidth and higher peak gain suitable for use in portable electronics. The effects of the periodic pattern and the reflection from the metal patches have also been investigated.

Effect of EBG Structures for Reducing Noise in Multi-Layer PCBs for Digital Systems

The effect of EBG structures in various noise source environments is investigated. In this paper a one-dimensional electromagnetic band gap structure (1D-EBG) has been used in the power/ground planes for isolating signal vias from noise sources. The 1D-EBG structure generates about -70dB isolation in the path between the noise source and the signal via structure, so as to minimize the coupling of the power/ground cavity noise into the signal lines. In the presence of EBG structures, the voltage noise and timing jitter are significantly reduced for periodic noise sources. However, for random noise sources, the voltage noise and timing jitter can increase in the presence of EBG structures. This paper quantifies this effect

Switching Noise Suppression in Mixed Signal System Applications Using Electromagnetic Band Gap (EBG) Synthesizer

Electromagnetic band gap (EBG) synthesizer using genetic algorithm has been applied for noise suppression in mixed signal system applications. EBGs have been successfully synthesized, designed, simulated, fabricated, and measured for noise isolation in mixed signal systems