Multiport VNA Measurements

This article presents some of the most recent multiport VNA measurement methodologies used to characterize these highspeed digital networks for signal integrity. There will be a discussion of the trends and measurement challenges of high-speed digital systems, followed by a presentation of the multiport VNA measurement system details, calibration, and measurement techniques, as well as some examples of interconnect device measurements. The intent here is to present some general concepts and trends for multiport VNA measurements as applied to computer system board-level interconnect structures, and not to promote any particular brand or produc

A neural probe with up to 966 electrodes and up to 384 configurable channels in 0.13 μm SOI CMOS

In vivo recording of neural action-potential and local-field-potential signals requires the use of high-resolution penetrating probes. Several international initiatives to better understand the brain are driving technology efforts towards maximizing the number of recording sites while minimizing the neural probe dimensions. We designed and fabricated (0.13-μm SOI Al CMOS) a 384-channel configurable neural probe for large-scale in vivo recording of neural signals. Up to 966 selectable active electrodes were integrated along an implantable shank (70 μm wide, 10 mm long, 20 μm thick), achieving a crosstalk of −64.4 dB. The probe base (5 × 9 mm2) implements dual-band recording and a 1

Development of Reduced Complexity Models for Electromagnetic Modeling

The current and field distributions of various structures can be calculated using full-wave numerical modeling codes. However, this approach is limited by the complex models and extensive computational resources required to analyze the details of each structure. In addition, brute-force modeling of the entire geometry provides relatively little physical insight into the electromagnetic interference (EMI) source mechanisms. Alternatively an effective equivalent model can be obtained by eliminating sources and structures that do not contribute significantly to the radiated emissions and focusing on the features that could possibly be significant sources of EMI. Equivalent models are generally much simpler than model-everything full-wave models and provide physical insight into the features that have the greatest impact on radiated emissions. This dissertation includes four chapters on development of reduced complexity models for the modeling of antennas and printed circuit board (PCB) structures. In the first chapter, a simplified model for normal mode helical antennas is proposed. In this model, the highly curved structure of the helix is replaced with straight wires and lumped elements. The simplified model can be used to reduce the complexity of full-wave models that include a helical antenna. It also can be used to estimate the performance of a helical antenna without full-wave modeling of the helical structure. The second chapter describes a model for determining the common-mode currents on cables attached to a PCB that is based on the concept of imbalance difference. The imbalance difference model is derived from research that shows that changes in geometrical imbalance cause differential- to common-mode conversion. The imbalance difference model can be used to estimate the radiated emissions from trace-board structures due to common-mode currents induced on attached cables. The third chapter introduces a new closed-form expression for estimating the maximum radiated emissions from the board-source-cable structure. This expression is based on two improvements to a closed-form expression in a 2008 paper published in the IEEE Transactions on EMC. The accuracy of the estimate for larger frequency ranges is improved by using an expression for the envelope of F(è, k, lant) that equals the maximum value at every resonant frequency. A modified expression for calculating the effective length of the board improves the accuracy of the estimate when applied to nearly square boards. In the forth chapter, a modeling technique is proposed to speed up the analysis of PCBs with coupled microstrip lines that induce common-mode currents on attached cables. Based on the concept of imbalance difference, differential-mode sources are converted to equivalent common-mode sources that drive the attached cable and the PCB reference plane. A closed-form expression is also developed based on the imbalance difference model to estimate the maximum radiated emissions from the PCB

An Approach to Assess Solder Interconnect Degradation Using Digital Signal

Department of Human and Systems EngineeringDigital signals used in electronic systems require reliable data communication. It is necessary to monitor the system health continuously to prevent system failure in advance. Solder joints in electronic assemblies are one of the major failure sites under thermal, mechanical and chemical stress conditions during their operation. Solder joint degradation usually starts from the surface where high speed signals are concentrated due to the phenomenon referred to as the skin effect. Due to the skin effect, high speed signals are sensitive when detecting the early stages of solder joint degradation. The objective of the thesis is to assess solder joint degradation in a non-destructive way based on digital signal characterization. For accelerated life testing the stress conditions were designed in order to generate gradual degradation of solder joints. The signal generated by a digital signal transceiver was travelling through the solder joints to continuously monitor the signal integrity under the stress conditions. The signal properities were obtained by eye parameters and jitter, which represented the characteristics of the digital signal in terms of noise and timing error. The eye parameters and jitter exhibited significant increase after the exposure of the solder joints to the stress conditions. The test results indicated the deterioration of the signal integrity resulted from the solder joint degradation, and proved that high speed digital signals could serve as a non-destructive tool for sensing physical degradation. Since this approach is based on the digital signals used in electronic systems, it can be implemented without requiring additional sensing devices. Furthermore, this approach can serve as a proactive prognostic tool, which provides real-time health monitoring of electronic systems and triggers early warning for impending failure.ope

Improved attenuation and crosstalk modeling techniques for high-speed channels

”As digital systems are moving in the direction of faster data transmission rate and higher density of circuits, the problem of the far-end crosstalk (FEXT) and frequency-dependent attenuation are becoming the major factors that limit signal integrity performance. This research is focusing on providing several more comprehensive and accurate modeling approaches for striplines on fabricated printed circuit board (PCB). By characterizing the dielectric permittivity of prepreg and core, dielectric loss tangent, and copper foil surface roughness using measurement data, a better agreement between the stripline model and measurement is achieved. First, a method is proposed to extract dielectric loss tangent using coupled striplines’ measured S-parameters and cross-section geometry. By relating modal attenuation factors to the ratio between the differential and common mode per-unit-length resistances, the unknwon surface roughness contribution is eliminated and the contributions of dielectric and conductor loss are separated. In addition, an improved surface roughness modeling approach is proposed by analyzing the microscopical cross-sectional image of the stripline. By combining the characterized surface roughness information and the extracted dielectric properties, the modeled attenuation factor is match with the measurement data. At last, an approach is introduced to extract the dielectric permittivity of prepreg and core. Using known cross-sectional geometry and measured phase of the coupled stirplines under test, the capacitance components in prepreg and core are separated using 2D solver models. Using the stripline model with inhomogeneous dielectric material, more accurate FEXT modeling results are obtained”--Abstract, page iv

Non Contact Test Points - A high frequency measurement technique for printed circuit boards

A rising problem within electronics today is that, since the frequencies have increased dramatically, it is now very difficult to measure signals. If a traditional probe is used, then the direct contact will destroy the signal. The general idea behind this master thesis project is to make use of the crosstalk between transmission lines to create non contact test points. This thesis aims to evaluate different designs, in order to optimize the crosstalk, and also make use of signal processing to recover the original signal. Firstly, the problem was tackled with simulations and the results were analyzed in an attempt to optimize the design. Secondly, an actual circuit board was produced and the process was tested in reality. It turned out that the idea of non contact test points was solid, and it is shown in the report that good measurements can be acquired with little effect upon the original signal

Investigations on electromagnetic noises and interactions in electronic architectures : a tutorial case on a mobile system

Electromagnetic interactions become critic in embedded and smart electronic structures. The increase of electronic performances confined in a finite volume or support for mobile applications defines new electromagnetic environment and compatibility configurations (EMC). With canonical demonstrators developed for tutorials and EMC experiences, this paper present basic principles and experimental techniques to investigate and control these severe interferences. Some issues are reviewed to present actual and future scientific challenges for EMC at electronic circuit level

Thin-film VCSEL and optical interconnection layer fabrications for fully embedded board level optical interconnects

textSemiconductor technology has been splendid evolved. As a consequence of, massive data traffic is required in system level. However copper based interconnection reached the upper limit of data transfer rate and can not provide enough bandwidth for high performance system. Copper based interconnection in long haul application was replaced to optical fiber. Optical interconnection in system level is generally considered as an alternative to provide high bandwidth. However, unlike long haul application, optical interconnection in system level encountered many problems such as compatibility, robustness and packaging difficulty. The compatibility to current electrical board system and packaging difficulty must be solved. This dissertation describes a fully embedded board level optical interconnection, which can solve many problems, components fabrication and hybrid integration with electrical layers. Thin-film VCSEL array and flexible optical waveguide are demonstrated. The optical interconnection layer integrated with thin-film VCSEL and photo-detector arrays is demonstrated.Electrical and Computer Engineerin

System level power integrity transient analysis using a physics-based approach

With decreasing supply voltage level and massive demanding current on system chipset, power integrity design becomes more and more critical for system stability. The ultimate goal of well-designed power delivery network (PDN) is to deliver desired voltage level from the source to destination, in other words, to minimize voltage noise delivered to digital devices. The thesis is composed of three parts. The first part focuses on-die level power models including simplified chip power model (CPM) for system level analysis and the worst scenario current profile. The second part of this work introduces the physics-based equivalent circuit model to simplify the passive PDN model to RLC circuit netlist, to be compatible with any spice simulators and tremendously boost simulation speed. Then a novel system/chip level end-to-end transient model is proposed, including the die model and passive PDN model discussed in previous two chapters as well as a SIMPLIS based small signal VRM model. In the last part of the thesis, how to model voltage regulator module (VRM) is explicitly discussed. Different linear approximated VRM modeling approaches have been compared with the SIMPLIS small signal VRM model in both frequency domain and time domain. The comparison provides PI engineers a guideline to choose specific VRM model under specific circumstances. Finally yet importantly, a PDN optimization example was given. Other than previous PDN optimization approaches, a novel hybrid target impedance concept was proposed in this thesis, in order to improve system level PDN optimization process --Abstract, page iv