Arif Ege Engin

Multilayered Finite-Difference Method (MFDM) for Modeling of Package and Printed Circuit Board Planes

Power/ground planes in electronic packaging can be a major factor for noise coupling. There can be noise coupling not only in the transversal direction between two planes, but also vertically from one plane pair to another through the apertures and via holes. Due to the large size of the power/ground planes, it is difficult to analyze them using full-wave simulators. It is known that the finite-difference solution of the Helmholtz equation provides a faster approach with comparable accuracy. For multilayered planes and arbitrary geometries with aperture coupling, we present a multilayered finite-difference method (MFDM). It provides an accurate representation of wrap-around currents, which have not been modeled earlier, for large cutouts. Estimation of the influence of such coupling effects are essential especially for a successful design of mixed-signal systems. This method allows to consider realistic structures, which would be prohibitive to simulate using full-wave simulators.

Power transmission lines: A new interconnect design to eliminate simultaneous switching noise

A major bottleneck in high-speed signaling is the simultaneous switching noise (SSN), which is caused by simultaneously switching output buffers. SSN is a result of the coupling between the signal lines and the power delivery network (PDN) in off-chip signaling. This coupling occurs at discontinuities of the transmission line, wherever there is an interruption of the current return path. A particular location where there is a return path discontinuity is the output buffer that is connected to a transmission line. To reduce this discontinuity, current designs try to maintain a low- impedance PDN for the I/O lines up to the output buffers on the chip. This requires a complicated design of the package and interconnections using, for example, planes for the PDN and decoupling capacitors on the package. For GHz signaling, it can be very difficult to maintain sufficiently low impedance. This paper presents a new PDN design, called as the power transmission line, which overcomes these problems.

Design, Modeling, and Characterization of Embedded Capacitor Networks for Core Decoupling in the Package

Embedded passives are gaining in importance due to the reduction in size of electronic products. Capacitors pose the biggest challenge for integration in packages due to the large capacitance required for decoupling high performance circuits. Surface mount discrete (SMD) capacitors become ineffective charge providers above 100 MHz due to the increased effect of loop inductance. This paper focuses on the importance of embedded capacitors above this frequency. Modeling, measurements, and model to hardware correlation of these capacitors are shown. Design and modeling of embedded capacitor arrays for decoupling processors in the midfrequency band (100 MHz-2 GHz) is also highlighted in this paper.

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

Improvements in Noise Suppression for I/O Circuits Using Embedded Planar Capacitors

The performance of embedded planar capacitors in noise suppression of input/output (I/O) circuits and improvements in board impedance profile have been investigated in this paper. Simultaneous switching noise (SSN) is a critical issue in todays systems and this paper shows performance improvements by introducing thin planar embedded capacitors in the board stack up. Measurement and modeling results by including the effects of transmission lines and the power ground plane pairs in the board stack up in the gigahertz range quantify the performance of the embedded capacitors.

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.

Analysis and Design of Electromagnetic Bandgap (EBG) Structures for Power Plane Isolation Using 2D Dispersion Diagrams and Scalability

Simultaneous switching noise (SSN) is one of the major bottlenecks for successful design of high-performance systems. Especially mixed-signal designs are very sensitive to SSN due to the low voltage levels applied in analog circuits. One way of isolation is by placing the digital and analog domains far from each other. Even then, the power planes can transfer noise voltages both vertically and horizontally through out the board and total board area is a major concern in microminiaturized convergent systems. Electromagnetic bandgap structures (EBG) have been successfully applied for such isolation. Although any periodical shape can be used for isolation, only a few shapes have been reported, with various analysis methods. We present a new EBG with narrow slits, which shows a higher attenuation constant compared with existing structures. We also present a new analysis methodology for 2D EBG structures. Finally, a method to scale such EBG structures for different stopband requirements is introduced

Finite difference modeling of multiple planes in packages

Power/ground planes in electronic packaging can be a major factor for noise coupling. There can be noise coupling not only in the transversal direction between two planes, but also vertically from one plane pair to another through the apertures and via holes. Due to the large size of the power/ground planes, it is difficult to analyze them using full-wave simulators. It is known that the finite difference solution of the Helmholtz equation provides a faster approach with a comparable accuracy. This paper presents new circuit models for a single plane pair based on the finite difference method: T- and X-models. It also presents a modeling approach for multiple plane pairs that are coupled through apertures

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.