Coupling Between Differential Signals and the DC Power-Bus in Multilayer PCBs

Differential and common-mode transfer impedances are proposed herein to analyze noise coupled to (from) the dc power-bus from (to) via transitions in differential signals. Expressions for the two transfer impedances in terms of conventional single-ended transfer impedances are derived and verified through measurements, full-wave finite-difference time-domain (FDTD) simulations and an analytical cavity model. Some properties of the differential and common-mode transfer impedances are investigated to facilitate engineering design. The impact of signal current imbalances on power-bus noise and the benefit of differential signals as compared to single-ended signals are quantified

SerDes channel crosstalk mitigation methodology with industrial implementation guidance

With the increasing data rate of digital circuits, the differential crosstalk degrades the signal integrity performance in PCBs drastically. Usually, in the trace area, crosstalk can be isolated by stitching vias and adding shielding ground vias can also shield coupling in the ball gate array (BGA) and pin field area. The traditional way to mitigation crosstalk in the BGA and pin field area through adding more ground vias between signal pairs or increasing the spacing in between, it demonstrated us the efficiency on crosstalk cancellation efficiency but it also increases the size of products and it would be contradictory to the trend of the industry and market. The design of new channels with far less crosstalk but maintained or increased space efficiency is necessary. The proposed pin patterns in this research mitigate the differential crosstalk dramatically, yet maintained or even increased the signal vias to ground vias ratio (S:G). S:G is the ratio of signal vias to ground pins in a specific area of PCBs, it can represent the space efficiency). Crosstalk cancellated by using the principle of symmetry on two adjacent differential signal pairs in the BGA and pin field region. Except for the pin patterns, corresponding trace routing for the advance patterns also been researched and designed to maintain the crosstalk cancellation benefits in the pin field area. After all, interconnections between the chip package and the newly designed PCB have been studied and verified regarding industry capability and reliability. This research proposed for the SerDes channel and the validating is under the SerDes operating circumstance --Abstract, page iii

Widely Tunable RF Frontend for the Universal Software Radio Peripheral: the MMP9000

This report presents the design and construction of a wideband transceiver in the context of an RF frontend for a software radio development platform, the Universal Software Radio Peripheral (USRP). This daughterboard is designed to operate at either full or half duplex modes over a frequency range of 100 MHz to 1.3 GHz or greater. It is fully integrated with both the USRP and GNU Radio, a free software radio development toolkit, to fully control the daughterboard via software

High-density interconnect technology assessment of printed circuit boards for space applications

High-density interconnect (HDI) printed circuit boards (PCBs) and associated assemblies are essential to allow space projects to benefit from the ever increasing complexity and functionality of modern integrated circuits such as field-programmable gate arrays, digital signal processors and application processors. Increasing demands for functionality translate into higher signal speeds combined with an increasing number of input/outputs (I/Os). To limit the overall package size, the contact pad pitch of the components is reduced. The combination of a high number of I/Os with a reduced pitch places additional demands onto the PCB, requiring the use of laser-drilled microvias, high-aspect ratio core vias, and small track width and spacing. Although the associated advanced manufacturing processes have been widely used in commercial, automotive, medical, and military applications, reconciling these advancements in capability with the reliability requirements for space remains a challenge. Two categories of the HDI technology are considered: two levels of staggered microvias (basic HDI) and (up to) three levels of stacked microvias (complex HDI). In this article, the qualification of the basic HDI technology in accordance with ECSS-Q-ST-70-60C is described. At 1.0-mm pitch, the technology passes all testing successfully. At .8-mm pitch, failures are encountered during interconnection stress testing and conductive anodic filament testing. These failures provide the basis for updating the design rules for HDI PCBs

Wideband characterization of printed circuit board materials up to 50 GHz

A traveling-wave technique developed a few years ago in the Missouri S&T EMC Laboratory has been employed until now for characterization of PCB materials over a broad frequency range up to 30 GHz. This technique includes measuring S-parameters of the specially designed PCB test vehicles. An extension of the frequency range of printed circuit board laminate dielectric and copper foil characterization is an important problem. In this work, a new PCB test vehicle design for operating up to 50 GHz has been proposed. As the frequency range of measurements increases, the analysis of errors and uncertainties in measuring dielectric properties becomes increasingly important. Formulas for quantification of two major groups of errors, repeatability (manufacturing variability) and reproducibility (systematic) errors, in extracting dielectric constant (DK) and dissipation factor (DK) have been derived, and computations for a number of cases are presented. Conductor (copper foil) surface roughness of PCB interconnects is an important factor, which affects accuracy of DK and DF measurements. This work describes a new algorithm for semi-automatic characterization of copper foil profiles on optical or scanning electron microscopy (SEM) pictures of signal traces. The collected statistics of numerous copper foil roughness profiles allows for introducing a new metric for roughness characterization of PCB interconnects. This is an important step to refining the measured DK and DF parameters from roughness contributions. The collected foil profile data and its analysis allow for developing design curves , which could be used by SI engineers and electronics developers in their designs --Abstract, page iii

Causal RLGC( Ƒ ) Models for Transmission Lines from Measured S-Parameters

Frequency-dependent causal RLGC(f) models are proposed for single-ended and coupled transmission lines. Dielectric loss, dielectric dispersion, and skin-effect loss are taken into account. The dielectric substrate is described by the two-term Debye frequency dependence, and the transmission line conductors are of finite conductivity. In this paper, three frequency-dependent RLGC models are studied. One is the known frequency-dependent analytical RLGC model ( RLGC-I), the second is the RLGC(f) model (RLGC-II) proposed in this paper, and the third (RLGC-III) is same as the RLGC -II, but with causality enforced by the Hilbert transform in frequency domain. The causalities of the three RLGC models are corroborated in the time domain by examining the propagation of a well-defined pulse through three different transmission lines: a single-ended stripline, a single-ended microstrip line, and an edge-coupled differential stripline pair. A clear time-domain start point is shown on each received pulse for the RLGC-II model and the RLGC-III model, where their corresponding start points overlap. This indicates that the proposed RLGC(f) model (RLGC-II) is causal. Good agreement of simulated and measured S-parameters has also been achieved in the frequency domain for the three transmission lines by using the proposed frequency-dependent RLGC (f) model

RF and Microwave Measurements

open1noBasic theory and techniques are concentrated mostly in the first four chapters, where definitions, formulas and references are collected aiming at giving a thorough overview of the most relevant topics: circuit theory, material properties, transmission lines, signal analysis and spectral analysis, including random processes, probability and statistics. The central chapters 5, 6 and 7 deals with three important elements of setups and experiments: cables, printed circuit boards and connectors. The influence on the overall measurement, their modeling and characterization are discussed, keeping an eye on applicable standards. The last four chapters cover advanced aspects of scattering parameters, differential lines and mixed modes, and the use and performance of spectrum analyzer and vector network analyzer.openA. MariscottiMariscotti, A

CAD model extraction of PCB signal discontinuity using a circuit extraction approach based on mixed-potential integral equation formulation

In high-speed digital design, signal via transitions on printed circuit boards (PCBs) are becoming an important signal integrity issue. Efficient and accurate models for via transitions are necessary to analyze high bit-rate digital circuit system. The circuit extraction approach based on a mixed-potential integral equation formulation (CEMPIE) is an extension of the Partial Element Equivalent Circuit approach (PEEC) to general multi-layered media. CEMPIE was further developed to include the horizontal current components on the vertical surface and extended to model the discontinuities on multilayer PCBs. A procedure of building SPICE models for signal via transitions between printed circuit board layers was developed. The method of extracting SPICE model parameters from full-wave simulation tool was studied. The validity of SPICE models was studied by comparing solutions from SPICE models with solutions from full-wave simulations. This procedure was further used for building SPICE models for via transitions in differential signaling --Abstract, page iii

Wideband characterization of printed circuit board materials up to 50 GHz

A traveling-wave technique developed a few years ago in the Missouri S&T EMC Laboratory has been employed until now for characterization of PCB materials over a broad frequency range up to 30 GHz. This technique includes measuring S-parameters of the specially designed PCB test vehicles. An extension of the frequency range of printed circuit board laminate dielectric and copper foil characterization is an important problem. In this work, a new PCB test vehicle design for operating up to 50 GHz has been proposed. As the frequency range of measurements increases, the analysis of errors and uncertainties in measuring dielectric properties becomes increasingly important. Formulas for quantification of two major groups of errors, repeatability (manufacturing variability) and reproducibility (systematic) errors, in extracting dielectric constant (DK) and dissipation factor (DK) have been derived, and computations for a number of cases are presented. Conductor (copper foil) surface roughness of PCB interconnects is an important factor, which affects accuracy of DK and DF measurements. This work describes a new algorithm for semi-automatic characterization of copper foil profiles on optical or scanning electron microscopy (SEM) pictures of signal traces. The collected statistics of numerous copper foil roughness profiles allows for introducing a new metric for roughness characterization of PCB interconnects. This is an important step to refining the measured DK and DF parameters from roughness contributions. The collected foil profile data and its analysis allow for developing design curves , which could be used by SI engineers and electronics developers in their designs --Abstract, page iii