Bruce Archambeault

The EM Side-Channel(s)

We present results of a systematic investigation of leakage of compromising information via electromagnetic (EM) emanations from CMOS devices. These emanations are shown to consist of a multiplicity of signals, each leaking somewhat different information about the underlying computation. We show that not only can EM emanations be used to attack cryptographic devices where the power side-channel is unavailable, they can even be used to break power analysis countermeasures.

Physics-Based Via and Trace Models for Efficient Link Simulation on Multilayer Structures Up to 40 GHz

Analytical models for vias and traces are presented for simulation of multilayer interconnects at the package and printed circuit board levels. Vias are modeled using an analytical formulation for the parallel-plate impedance and capacitive elements, whereas the trace-via transitions are described by modal decomposition. It is shown that the models can be applied to efficiently simulate a wide range of structures. Different scenarios are analyzed including thru-hole and buried vias, power vias, and coupled traces routed into different layers. By virtue of the modal decomposition, the proposed method is general enough to handle structures with mixed reference planes. For the first time, these models have been validated against full-wave methods and measurements up to 40 GHz. An improvement on the computation speed of at least two orders of magnitude has been observed with respect to full-wave simulations.

Signal Integrity Design for High-Speed Digital Circuits: Progress and Directions

This paper reviews recent progress and future directions of signal integrity design for high-speed digital circuits, focusing on four areas: signal propagation on transmission lines, discontinuity modeling and characterization, measurement techniques, and link-path design and analysis.

Analysis of power/ground-plane EMI decoupling performance using the partial-element equivalent circuit technique

The design of printed circuit (PC) boards with decoupling capacitors has been the subject of debate and different opinions for many years. The design and electrical impact of the capacitors has been difficult to separate from all other electrical interactions occurring on a conventional PC board populated with integrated circuits. This work demonstrates how the partial-element equivalent circuit (PEEC) modeling technique can be used to accurately predict the performance of various decoupling design strategies. Computer modeling using the PEEC approach is very flexible due to the ease of mixing physical geometries with a large number of circuit elements. Also, the compute time for such practical mixed EM and circuit problems are relatively short. Using this technique, the usual iteration between a number of different designs of test boards can be avoided. We show that the change of the voltage across the PC board, or the voltage gradient, can be used as an effective tool for the improvement of the decoupling efficiency.

Modeling of Shielding Composite Materials and Structures for Microwave Frequencies

Composites containing conducting inclusions are required in many engineering applications, especially, for the design of microwave shielding enclosures to ensure electromagnetic compatibility and electromagnetic immunity. Herein, multilayer shielding structures are studied, with both absorbing and re∞ecting composite layers. In this paper, flber-fllled composites are considered. For modeling absorbing composites with low concentration of conducting cylindrical inclusions (below the percolation threshold), the Maxwell Garnett theory is used. For re∞ecting layers, when concentration of inclusions is close to or above the percolation threshold, the McLachlan formulation is used. Frequency dependencies for an efiective permittivity are approximated by the Debye curves using a curve-fltting procedure, in particular, a genetic algorithm.

A simple finite-difference frequency-domain (FDFD) algorithm for analysis of switching noise in printed circuit boards and packages

Simultaneous switching noise (SSN) compromises the integrity of the power distribution structure on multilayer printed circuit boards (PCB). Several methods have been used to investigate SSN. These methods ranged from simple lumped circuit models to full-wave (dynamic) three-dimensional Maxwell equations simulators. In this work, we present an efficient and simple finite-difference frequency-domain (FDFD) based algorithm that can simulate, with high accuracy, the capacity of a PCB board to introduce SSN. The FDFD code developed here also allows for simulation of real-world decoupling capacitors that are typically used to mitigate SSN effects at sub 1 GHz frequencies. Furthermore, the algorithm is capable of including lumped circuit elements having user-specified complex impedance. Numerical results are presented for several test boards and packages, with and without decoupling capacitors. Validation of the FDFD code is demonstrated through comparison with other algorithms and laboratory measurements.

Review of Printed-Circuit-Board Level EMI/EMC Issues and Tools

A comprehensive review of printed circuit board (PCB) electromagnetic compatibility (EMC) issues, analysis techniques, and possible solutions would fill a large book or more. This review takes a quick look at where the technology of PCB EMC control has been, where it is today, and where it needs to go for the future. As data rates on PCBs have increased, new problems have arisen, requiring new analysis techniques and new solutions. Further development will be needed to keep up with the ever-increasing data rates and smaller form factors.

EMI resulting from signal via transitions through the DC power bus

Signal routing with layer changes through via transitions are common in multi-layer printed circuit board (PCB) design. For high-speed signals that transition through the internal parallel planes comprising the DC power bus, the return current has to switch from one reference plane to another reference plane. The return current discontinuity at the via excites the DC power bus and can result in a power bus noise problem, as well as an EMI problem. EMI resulting from the signal transitions through a DC power bus is studied herein. Measurements were made on an experimental board, and numerical modeling was used to study the EMI resulting from the excited DC power bus. The effects of local and global decoupling as an EMI mitigation approach were also studied. In addition, noise coupled to I/O lines, and EMI were studied for a test board with varying layer thickness between the power and ground planes.

Compact Configuration for Common Mode Filter Design based on Planar Electromagnetic Bandgap Structures

A planar electromagnetic bandgap configuration of a compact common mode filter that is laid out on printed circuit board is studied. This filter is used to mitigate the common mode noise traveling on high-speed differential signal traces. These differential signal lines may be connected to I/O connectors and cables and small amounts of common mode noise can result in significant electromagnetic emissions. The filter is obtained by a very simple planar geometry based on the electromagnetic bandgap structures. A cavity made by a rectangular/square patch (together with a solid plane underneath) has a well known and predictable resonant behavior; the coupling between the differential pair routed on top of the patterned plane and the patch cavity, occurring when the traces cross the gap between adjacent patches, is used to reduce the energy associated with the propagation of the common mode noise. The properties of this filter are studied taking into account the layout of a real differential microstrip and the number of gap crossings. A compact configuration is proposed. Time domain simulations validate the suggested layout approach.

Frequency-dependent via inductances for accurate power distribution network modeling

In power distribution network (PDN) modeling, interconnection inductance can play a critical role. It often determines the effectiveness of a component, such as a decoupling capacitor. This paper studies a typical one-plane-pair PDN structure with parallel power and ground planes and vertical vias in between. This work improves the conventional lumped circuit model for the PDN by introducing a model for the inductance of each via that is frequency-dependent. This frequency dependency is obtained from a rigorous cavity model formulation. The improved lumped circuit model is validated with the cavity model and the HFSS full-wave model. Further, the frequency-dependent mutual inductance between two vias can have either a positive or a negative value depending on via locations in the PDN structure, which is an interesting property that has not been reported.