Edward Wheeler

On finding the optimal number of decoupling capacitors by minimizing the equivalent inductance of the PCB PDN

PCB-PDN design remains a challenge with the reducing noise margins. One aspect of PDN design is finding the number of decoupling capacitors required for each power rail. As more capacitors are added, the mid frequency equivalent inductance in the impedance of the PCB-PDN converges to a minimum value for each placement pattern. This convergence is studied for different placement patterns to find the least number of capacitors required to satisfy a certain convergence criteria. A first principle method is used resonant cavity model for the analysis.

Plane-Pair PEEC Model for Power Distribution Networks With Sub-Meshing Techniques

We present an improved plane-pair partial element equivalent circuit (PEEC) model for power distribution network modeling based on the PEEC formulation. The model can include via connections, decoupling capacitor macro-models, and discontinuities such as holes in the plane-pairs. An efficient approximate inductance sub-meshing model is described for large printed circuit plane-pairs with complex geometries and numerous vias. The modified nodal analysis (MNA) used leads to a flexible circuit solution where we can compute inductances, resistances, impedances, or other circuit models, including dc solutions. The MNA equations include effective optimizations such as the placement of capacitors. Today, a large class of methods are available based on numerous formulations including finite-difference time-domain, finite-element method, integral equation model, and cavity models. Each of the approaches has its own type of problems for which it is most suitable.

Effectiveness of PCB Simulation in Teaching High-Speed Digital Design

Signal integrity for high-speed digital design at the printed-circuit board (PCB) level is an issue of increasing importance in electronic design that requires coverage in more undergraduate classes. This paper describes how simulation tools offer an economical alternative to hardware-based experiments in undergraduate courses in high speed design. A simulation tool, Hyperlynx, has been used in our high-speed digital design class to help students understand fundamental concepts and ideas in signal integrity as well as to experiment with different techniques for maintaining signal integrity in a PCB design. We present examples in which traditional approaches employing only closed-form expressions can be effectively supplemented with simulation to help students gain a deeper understanding of basic concepts such as time-of-flight, parasitic parameters, nonlinear driver and receiver models, characteristic impedance, per-unit- length parameters, termination techniques, and crosstalk.

CSRR common-mode filtering structures in multilayer printed circuit boards

When complementary split ring resonator (CSRR) structures are used as common-mode (CM) filters in multilayer printed circuit board (PCB) environments, their effectiveness in filtering CM signals suffers as CM energy couples to the parallel plane waveguide which can be formed by the conducting layers below the CSRR layer. Via fences can largely prevent this coupling to allow some recovery of CM filtering effectiveness in addition to eliminating the signal integrity (SI) hazard introduced by the presence of excited parallel plane waveguide modes. Simulation and measurement results in initial investigations of filtering structures indicate CM filtering between 7 and 8 GHz and differential-mode (DM) transmission effective to 16 GHz. Simulations are provided showing that the via fences allow cascading for filtering at multiple frequencies or else to broaden filtering bandwidths. Next steps show simulations of CM filtering structures in differential links with effective DM transmission at higher frequencies.

Mitigating the threat of crosstalk and unwanted radiation when using electromagnetic bandgap structures to suppress common mode signal propagation in PCB differential interconnects

Common-mode noise in high-speed differential signaling results in significant signal integrity and EMI concerns. Past work has shown that common-mode filters based on electromagnetic bandgap (EBG) structures can be implemented using standard PCB technology and are effective in suppressing common mode transmission on differential interconnects. This common-mode energy, when filtered, can result in crosstalk or unintentional radiation. In the work described here, the radiation mechanisms in the electromagnetic bandgap structure are examined and a solution involving via stitching and via fences is proposed.

Plane-pair PEEC models for PDN using sub-meshing

In this paper, we present an improved plane-pair model for power distribution system modeling using the partial element equivalent circuit approach. The modified nodal analysis with a sub-meshing strategy leads to an efficient and accurate circuit solution in both the frequency domain and time domain.

A required EMC course for computer engineering undergraduates

A required junior-level course on electromagnetic compatibility and signal integrity has been added to our computer engineering curriculum. The goal of the course is to prepare our students for further study in high-speed design and to provide them with a competitive advantage in the marketplace. The course is, of necessity, a compromise between coverage of electromagnetics theory and the breadth of the discussion of EMC practice and techniques. The focus is on those aspects of EMC related to high-speed digital systems and upon EMC laboratory measurements and techniques. This paper reports the course, laboratories; lessons learned and anticipated future directions for the course

Work in progress - interdisciplinary laboratory-based advanced MEMS course for undergraduates

We have developed a two-course sequence in MEMS for undergraduate students at Rose-Hulman. The second course in this two-course MEMS sequence - and the focus of this WIP - has an integral term-length laboratory project. The study of MEMS provides a rich environment in which to provide students with truly interdisciplinary work and to present them with design problems having real constraints. Challenges include faculty coordination in these team-taught courses and delivering educational materials to a relatively disparate student audience.

Incorporation of AsSe centers in ZnSe far from equilibrium

Abstract An investigation employing nuclear transmutation to probe the effects of copper doping in ZnSe is presented. Three experimental techniques are developed in the investigation. With the first, as-grown ZnSe is irradiated with thermal neutrons which results, after thermal annealing, in the incorporation of Cu Zn centers. Observations are consistent with isolated Cu Zn being involved in the copper red and copper green emissions in ZnSe but not in the I d 1 excitonic emission. With the second, it is shown that zinc annealing can be used effectively in investigations involving the irradiation of as-grown ZnSe since the zinc annealing treatment significantly reduces background PL emissions in bulk ZnSe. The third technique employs homoepitaxial ZnSe layer growth from previously irradiated elemental sources. The epitaxial layers display no dominant I d 1 excitonic emission and a very low level of deep emissions. Because, with the techniques described here, the copper atoms are introduced at zinc sites after crystal growth processes are complete, the copper atoms are not able to interact with other dopants or lattice defects during growth as they can when incorporated by other means. The absence of interactions during crystal growth permits the unambiguous incorporation, far from equilibrium, of isolated Cu Zn centers in ZnSe.

Common-mode filtering in multilayer printed circuit boards

Common mode (CM) conversion in differential communication links represents serious signal integrity (SI) and electromagnetic compatibility (EMC) hazards. Two types of common-mode filtering structures are investigated in this paper. The first employs complementary split ring resonator (CSRR) structures placed in the reference layer surrounded by via fences, and the second uses a composite right-/left-handed (CRLH) structure formed by placing metallic strips between the microstrip traces. Via fences were employed to surround the individual CSRR filtering structures, which allows cascading to either filter at multiple frequencies or else to broaden filtering bands. Via fences also prevent filtered CM energy from exciting parallel-plane waveguide (PPW) modes which would degrade the boards EMC and SI environments.