A simple method for the evaluation of microwave surface loss of superconductive samples is discussed. The method allows the evaluation of small (∼1 cm×∼1 cm), flat samples over a broad range of temperatures. It can accurately characterize samples with surface resistances as low as 5 μΩ or as high as 1 mΩ at 10 GHz. In addition to high resolution, it has several advantages: sample preparation requirements are minimal; the current distribution within the sample under test is relatively uniform and can be accurately calculated; no other superconducting or normal conducting material is required for the resonator, so no additional corrections for such materials are needed; and the procedure is comparatively rapid and can be performed in the necktube of a liquid‐helium storage Dewar.

A parallel plate resonator technique for microwave loss measurements on superconductors

A theoretical model for the plasma erosion opening switch (PEOS) is presented which predicts its voltage, current and impedance history as a function of the input waveforms, geometry, and switch parameters. Scaling relations for the switch operation are developed from this model. System requirements for pulse compression and power multiplication using inductive storage are derived from a simple lumped circuit analysis and a transmission line analysis. These requirements are shown to be satisfied using the PEOS as a fast opening, vacuum switch in a configuration relevant for existing high‐power accelerators. The switch model is incorporated into a transmission line code for comparison with recent inductive storage experiments. Code results agree well with the data showing conduction times of ∼60 ns and switching times of ∼10 ns with peak currents of ∼600 kA.

Theoretical modeling of the plasma erosion opening switch for inductive storage applications

This paper discusses a multichip module for future VLSI computer packages on which an array of silicon chips is directly attached and interconnected by high-density thin-film lossy transmission lines. Since the high-performance VLSI chips contain a large number of off-chip driver circuits which are allowed to switch simultaneously in operation, low-inductance on-module capacitors are found to be essential for stabilizing the on-module power supply. Novel on-module capacitor structures are therefore proposed, discussed, and evaluated. Material systems and processing techniques for both the thin-film interconnection lines and the capacitor structures are also briefly discussed in the paper. Development of novel defect detection and repair techniques has been identified as essential for fabricating the Thin-Film Module with practical yields.

The thin-film module as a high-performance semiconductor package

As circuit boards are increasingly required to transmit signals at higher and higher speeds, signal and power integrity become increasingly crucial. Rules of thumb that you have used over and over again to prevent signal loss no longer apply to these new, high-speed, high-density circuit designs. This leading-edge circuit design resource offers you the knowledge needed to quickly pinpoint transmission problems that can compromise your entire circuit design. Discussing both design and debug issues at gigabit per second data rates, the book serves as a practical reference for your projects involving high-speed serial signaling on printed wiring boards. Step-by-step, this book goes from reviewing the essentials of linear circuit theory, to examining practical issues of pulse propagation along lossless and lossy transmission lines. It provides detailed guidelines for crosstalk, attenuation, power supply decoupling, and layer stackup tradeoffs (including pad/antipad tradeoffs). Other key topics include the construction of etched conductors, analysis of return paths and split planes, microstrip and stripline characteristics, and SMT capacitors. Filled with on-the-job-proven examples, this hands-on reference is the book that you can turn to time and again to design out and troubleshoot circuit signal loss and impedance problems.

High-speed circuit board signal integrity

Standard design and construction practices used in building nuclear magnetic resonance (NMR) probes for the study of solid state samples become difficult if not entirely impractical to implement as the 1H resonance frequency approaches the self resonance frequency of commercial capacitors. We describe an approach that utilizes short variable transmission line segments as tunable reactances. Such an approach effectively controls stray reactances and provides a higher Q alternative to ceramic chip capacitors. The particular probe described is built to accommodate a 2.5 mm magic angle spinning rotor system, and is triply tuned to 13C, 15N, and 1H frequencies for use at 18.8 T (200, 80, and 800 MHz, respectively). Isolation of the three radio frequency (rf) channels is achieved using both a rejection trap and a transmission line notch filter. The compact geometry of this design allows three channels with high power handling capability to fit in a medium bore (63 mm) magnet. Extended time variable temperature operation is integral to the mechanical design, enabling the temperature control necessary for investigation of biological macromolecules. Accurate measurement of the air temperature near the sample rotor is achieved using a fiber optic thermometer, which does not interfere with the rf electronics. We also demonstrate that acceptable line shapes are only readily achieved using zero magnetic susceptibility wire in construction of the sample coil. Computer simulation of the circuit aided in the physical design of the probe. Representative data illustrating the efficiency, rf homogeneity, and signal to noise factor of the probe are presented.

Design of a triple resonance magic angle sample spinning probe for high field solid state nuclear magnetic resonance

Transmission lines and networks , Transmission lines and networks , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Walter Curtis Johnson

Papers

Transmission Lines and Networks