Quantifying the Effects on EMI and SI of Source Imbalances in Differential Signaling

Imbalances in differential signaling can introduce common-mode components, resulting in signal integrity (SI) problems as well as EMI problems. Three-port mixed-mode S-parameters are employed to quantify the impacts on EMI. The EMI problems caused by delay skew and slew rate skew are investigated

Study of Interconnect Vias by the Discrete Surface Integral Method

A non-orthogonal time-domain full-wave solver, is developed based on the Discrete Surface Integral (DSI) technique. Closed form expressions are derived for the coefficients used in the leap-frog computation scheme so that the DSI technique can be implemented as a generalized finite-difference procedure. This procedure is employed to investigate the propagation characteristics of a typical interconnect via in printed circuits. The numerically calculated scattering parameters show consistent behavior with measured results. A square via with equal area is also evaluated

Incorporating Two-Port Networks with S-Parameters into FDTD

A modeling approach for incorporating a two-port network with S-parameters in the finite-difference time-domain (FDTD) method is reported in this paper. The proposed method utilizes the time-domain Y-parameters to describe the network characteristics, and incorporates the Y-parameters into the FDTD algorithm. The generalized pencil-of-function (GPOF) technique is applied to improve the memory efficiency of this algorithm by generating a complex exponential series for the Y-parameters and using recursive convolution in the FDTD updating equations. A modeling example is given, which shows that this approach is effective and accurate. This modeling technique can be extended for incorporating any number of N-port networks in the FDTD modeling

FDTD Modeling Incorporating a Two-Port Network for I/O Line EMI Filtering Design

Electromagnetic interference (EMI) filters are often utilized on I/O lines to reduce high-frequency noise form being conducted off the printed circuit board (PCB) and causing EMI problems. The filtering performance is often compromised at high frequencies due to parasitics associated with the filter itself, or the PCB layout and interconnects. Finite difference time domain (FDTD) modeling can be used to quantify the effect of PCB layout and interconnects, as well as filter type, on the EMI performance of I/O line filtering. FDTD modeling of a T-type and π-type filter consisting of surface-mount ferrites and capacitors is considered herein. The FDTD method is applied to model PCB layout and interconnect features, as well as the lumped element components, including the nonlinear characteristics of ferrite surface-mount parts. The EMI filters with ferrites are included in the modeling by incorporating the time-domain Y-parameters of the two-port network into the FDTD time-marching equations. Good agreement between the FDTD modeling and S-parameter measurements supports the new FDTD algorithm for incorporating two-port networks

Lumped-Circuit Model Extraction for Vias in Multilayer Substrates

Via interconnects in multilayer substrates, such as chip scale packaging, ball grid arrays, multichip modules, and printed circuit boards (PCB) can critically impact system performance. Lumped-circuit models for vias are usually established from their geometries to better understand the physics. This paper presents a procedure to extract these element values from a partial element equivalent circuit type method, denoted by CEMPIE. With a known physics-based circuit prototype, this approach calculates the element values from an extensive circuit net extracted by the CEMPIE method. Via inductances in a PCB power bus, including mutual inductances if multiple vias are present, are extracted in a systematic manner using this approach. A closed-form expression for via self inductance is further derived as a function of power plane dimensions, via diameter, power/ground layer separation, and via location. The expression can be used in practical designs for evaluating via inductance without the necessity of full-wave modeling, and, predicting power-bus impedance as well as effective frequency range of decoupling capacitors

Dispersion Comparison for DSI- and Tensor-Based Nonorthogonal FDTD

An explicit formulation of the finite-difference time-domain-discrete surface integral (FDTD-DSI) technique has allowed a rigorous study of numerical dispersion for the method. The study shows that the DSI- and tensor-based FDTD methods do not have the same numerical dispersion relation. It also clarifies the recently reported discrepancies in the dispersion relation between the two approaches. This study also shows that the tensor-based FDTD algorithm exhibits better dispersion properties for a two-dimensional uniformly skewed mesh

Power Division by Element Design in a Circularly Polarized, Series-fed Array

The feasibility of designing a wideband circular polarized (CP) array of series-fed elements using the element geometry to control the array excitation has been demonstrated. The simple array of wideband, low-profile CP elements requires no phase-shifters and only sufficient feed lines for the interconnection of the elements in a series-fed array. A complicated network is not required to obtain the excitation coefficients for a specified design. Rather, the excitation coefficients can be realized by utilizing the geometric parameters of the individual elements

ANSERLIN. A Broad-Band, Low-Profile, Circularly Polarized Antenna

A technique is presented for improving the performance of low-profile, circularly polarized (CP) radiating-line antennas. The essential elements of the technique pertain to establishing a single traveling wave on an annular sector of conducting strip that is positioned parallel and close to a large conducting surface. The antenna is named the annular sector, radiating-line (ANSERLIN) antenna. Using this technique, the impedance bandwidth becomes so large that it no longer has any bearing on the operating bandwidth. Instead, the pattern shape and axial ratio become the factors that limit the bandwidth. Both senses of circular polarization can be transmitted or received from the same structure. Experimental results for two-port ANSERLIN antennas are presented. The method of exciting a traveling wave on the annular sector is discussed. Design parameters are given for an antenna that will produce a broadside axial ratio that is less than 0.5 dB at a specified frequenc