Fred Barlow

Bio: Fred Barlow is an academic researcher from University of Idaho. The author has contributed to research in topics: Power module & Fourier transform. The author has an hindex of 19, co-authored 88 publications receiving 1368 citations. Previous affiliations of Fred Barlow include Virginia Tech & Metropolitan State University of Denver.

Microelectronics and electronic packaging education and research at Virginia Tech

Abstract: Instruction and research at Virginia Tech, in the area of Microelectronics and Electronic Packaging, center around a core group of students and faculty in the Microelectronics Laboratory. This group offers courses in microelectronics with a strong emphasis on multichip module design and fabrication, interconnects, and electronic packaging, and include an introductory course in microelectronics as well as several graduate courses in electronic packaging, electronic devices, and microwave circuit design and fabrication. This paper outlines these instructional and research efforts as well as the capabilities of the Microelectronics laboratory. In addition, the courses structure and recent efforts to expand the microelectronics education to include integrated circuit fabrication, as well as advances in power electronic packaging will be discussed in this paper.

A new method for causality enforcement of DRAM package models using discrete hilbert transforms

Abstract: Causality verification and enforcement is an essential step in generating high speed electric package macromodels and it often accomplished in two steps: vector fitting measured system parameters into a rational function representation and then performing the Hilbert Transform integrations to check and if needed enforce causality. This procedure suffers from various approximation, truncation, and discretization errors. Besides, the measured or simulated system data are known only on the finite bandwidth, while the Hilbert Transform has to be computed on the infinite domain. To avoid these errors as well as inaccuracy of extrapolation of the transfer function to infinity, a new method is proposed to check and enforce causality by using raw bandlimited data that is extended periodically using a polynomial interpolation and computing the Hilbert Transform of the periodically extended data via accurate FFT.

A Study of Differential Signaling: Stable and Accurate Mixed-Mode Conversion and Extraction of Differential S-Parameters

Abstract: Low voltage differential signaling (LVDS) in high-speed digital systems is utilized to effectively reduce EMI and improve signal quality. Mixed-mode S-parameters are a more general way to characterize a differential network. Therefore, an accurate extraction of mixed-mode S-parameters from single-ended S- parameters is critical for Signal and Power Integrity co-simulation where SSN is generated mainly by high-frequency interconnects. The standard conversion between mixed-mode and single-ended S-parameters involves inversion of a transformation matrix. If there is no coupling, this transformation matrix is orthogonal and numerical inversion can be done accurately. In the presence of coupling, the transformation matrix depends on S-parameters and may become ill-conditioned, i.e. has high condition number, for some values of physical parameters resulting in unstable inversion of the transformation matrix and leading to highly inaccurate converted mixed-mode S-parameters. To analyze the possibility of ill-conditioning, we consider two cases: broadside coupled striplines and coupled microstrip pairs. We find that in both cases when two transmission lines are strongly coupled, the condition number becomes very large. In this case, regularized methods from the theory of ill-posed problems should be used, for example, the truncated SVD method, to obtain accurate mixed-mode S- parameters.

Process and material challenges associated with the next generation of LTCC based products

Abstract: Current trends in electronics are driving demands to decrease the overall size of circuitry and increase the functionality. A variety of different substrate technologies have been proposed to meet these demands. Low Temperature Cofired Ceramics (LTCC) is one of many technologies that offer the potential to solve this problem. LTCC is a mature and robust technology that is finding wide spread adoption in a number of key applications. However, all substrate technologies are continually refined in order to expand the capabilities and therefore expand market adoption. While LTCC has many advantages, there are many challenges involved in processing future products with ever-decreasing circuit feature sizes. In order to effectively exploit the advantages offered by LTCC and meet these demands, advancements in the state of the art are needed. This paper will discuss in detail the current technology limitations as they pertain to high frequency circuits as well as high density interconnect substrates used for digital systems. The impact of tape instability, printing tolerance, embedded passives, as well as layer-to-layer alignment will be discussed including potential solutions.

Modeling-based design optimization of wafer-level and chip-scale packaging for RF-MEMS devices

Abstract: A wafer-level chip-scale package for RF-MEMS devices - specifically RF-MEMS switches - has been developed that meets the criteria needed for encapsulation of these devices. The RF-MEMS devices within the package are of a coplanar waveguide (CPW) configuration and were designed for operation from 1 to 10 GHz. High resistivity silicon (HRS) and low temperature co-fired ceramic (LTCC) were chosen due to their ease of processing, mechanical properties, and electrical performance. Representative models of capping substrates for the RF-MEMS switches were developed to simulate and optimize the designs using Microwave Office from Applied Wave Research. Data were obtained from the models in the form of scattering or S-parameters. The results show that for substrates with thicknesses below 300 /spl mu/m, the electrical performance is acceptable for the use of HRS and LTCC as capping-substrate materials.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

A Survey of Wide Bandgap Power Semiconductor Devices

Abstract: Wide bandgap semiconductors show superior material properties enabling potential power device operation at higher temperatures, voltages, and switching speeds than current Si technology. As a result, a new generation of power devices is being developed for power converter applications in which traditional Si power devices show limited operation. The use of these new power semiconductor devices will allow both an important improvement in the performance of existing power converters and the development of new power converters, accounting for an increase in the efficiency of the electric energy transformations and a more rational use of the electric energy. At present, SiC and GaN are the more promising semiconductor materials for these new power devices as a consequence of their outstanding properties, commercial availability of starting material, and maturity of their technological processes. This paper presents a review of recent progresses in the development of SiC- and GaN-based power semiconductor devices together with an overall view of the state of the art of this new device generation.

Overview of Dual-Active-Bridge Isolated Bidirectional DC–DC Converter for High-Frequency-Link Power-Conversion System

Abstract: High-frequency-link (HFL) power conversion systems (PCSs) are attracting more and more attentions in academia and industry for high power density, reduced weight, and low noise without compromising efficiency, cost, and reliability. In HFL PCSs, dual-active-bridge (DAB) isolated bidirectional dc-dc converter (IBDC) serves as the core circuit. This paper gives an overview of DAB-IBDC for HFL PCSs. First, the research necessity and development history are introduced. Second, the research subjects about basic characterization, control strategy, soft-switching solution and variant, as well as hardware design and optimization are reviewed and analyzed. On this basis, several typical application schemes of DAB-IBDC for HPL PCSs are presented in a worldwide scope. Finally, design recommendations and future trends are presented. As the core circuit of HFL PCSs, DAB-IBDC has wide prospects. The large-scale practical application of DAB-IBDC for HFL PCSs is expected with the recent advances in solid-state semiconductors, magnetic and capacitive materials, and microelectronic technologies.

Eliminate Reactive Power and Increase System Efficiency of Isolated Bidirectional Dual-Active-Bridge DC–DC Converters Using Novel Dual-Phase-Shift Control

Abstract: This paper proposes a novel dual-phase-shift (DPS) control strategy for a dual-active-bridge isolated bidirectional DC-DC converter. The proposed DPS control consists of a phase shift between the primary and secondary voltages of the isolation transformer, and a phase shift between the gate signals of the diagonal switches of each H-bridge. Simulation on a 600-V/5-kW prototype shows that the DPS control has excellent dynamic and static performance compared to the traditional phase-shift control (single phase shift). In this paper, the concept of ldquoreactive powerrdquo is defined, and the corresponding equations are derived for isolated bidirectional DC-DC converters. It is shown that the reactive power in traditional phase-shift control is inherent, and is the main factor contributing to large peak current and large system loss. The DPS control can eliminate reactive power in isolated bidirectional DC-DC converters. In addition, the DPS control can decrease the peak inrush current and steady-state current, improve system efficiency, increase system power capability (by 33%), and minimize the output capacitance as compared to the traditional phase-shift control. The soft-switching range and the influence of short-time-scale factors, such as deadband and system-level safe operation area, are also discussed in detail. Under certain operation conditions, deadband compensation can be implemented easily in the DPS control without a current sensor.

Wearable Electrochemical Sensors and Biosensors: A Review

Abstract: This article reviews recent advances and developments in the field of wearable sensors with emphasis on a subclass of these devices that are able to perform highly-sensitive electrochemical analysis Recent insights into novel fabrication methodologies and electrochemical techniques have resulted in the demonstration of chemical sensors able to augment conventional physical measurements (ie heart rate, EEG, ECG, etc), thereby providing added dimensions of rich, analytical information to the wearer in a timely manner Wearable electrochemical sensors have been integrated onto both textile materials and directly on the epidermis for various monitoring applications owing to their unique ability to process chemical analytes in a non-invasive and non-obtrusive fashion In this manner, multi-analyte detection can easily be performed, in real time, in order to ascertain the overall physiological health of the wearer or to identify potential offenders in their environment Of profound importance is the development of an understanding of the impact of mechanical strain on textile- and epidermal (tattoo)-based sensors and their failure mechanisms as well as the compatibility of the substrate employed in the fabrication process We conclude this review with a retrospective outlook of the field and identify potential implications of this new sensing paradigm in the healthcare, fitness, security, and environmental monitoring domains With continued innovation and detailed attention to core challenges, it is expected that wearable electrochemical sensors will play a pivotal role in the emergent body sensor networks arena