From abstract: This paper describes a Bessel null technique to measure the frequency response of a frequency-modulated rf carrier and a program to automate frequency response measurements of signal generators with output frequencies from 0.450 to 2000 MHz. The measurements obtained using this technique are more precise than those obtained by a highly trained technician using a manual system.

From introduction: This note describes the design and construction of a coaxial thermal noise standard. The standard is designed to operate at the boiling point of liquid nitrogen with a noise temperature accurate to t 1 K in the frequency range from 1 GHz to 12.4 GHz.

From introduction: This note describes the design and error analysis of a WR10 thermal noise power standard. The standard is designed to operate at the boiling point of liquid nitrogen with a noise temperature accurate to plus or minus 1 K.

Abstract: This report presents the results of work at the National Bureau of Standards, Boulder, Colorado, to carefully evaluate, document, develop (when necessary), and describe the methodology for performing radiated susceptibility/vulnerability measurements using a reverberation chamber. The report describes the reverberation chamber theory of operation, construction, evaluation, functional operation, and use for performing immunity measurements. It includes an estimate of measurement uncertainties derived empirically from test results and from comparisons with anechoic chamber measurements. Finally, it discusses the limitations and advantages of the measurement technique to assist potential users in determining the applicability for this technique to their electromagnetic compatibility (EMC) measurement needs.

From introduction: In this report the following will he discussed: (1) design consideration of the broadband magnetic field sensor, (2) overall design of the magnetic field meter, (3) performance of the meter, (4) calibration and operating procedures, (5) alignment and adjustment procedures, and (6) summary and conclusions.

From abstract: This paper presents the conflicts in the design and gives a solution. The complete evaluation requires assembly of the proposed apparatus to assess final accuracy.

Abstract: This report describes a system based on electromagnetic-acoustic transducers (EMATs) as an approach to automated nondestructive evaluation of thick weldments (>25 mm). Good signal-to-noise ratios, often a problem with EMATs, were possibTe through careful design of the transducers and associated electronic circuits and the use of signal averaging. At 454 kHz, the transducers produce shear-horizontal waves of approximately 7-mm wavelength in steel. The long wavelength permits determination of through-thickness flaw depth from the amplitudes of scattered ultrasonic waves. A minicomputer controlled transducer positioning and acquired the digitized ultrasonic waveforms for synthetic aperture processing. The synthetic aperture technique further improved signal quality and yielded flaw localization through the weld thickness. Measurements on artificial flaws demonstrated a detectability threshold of 0.5 mm (through thickness) and sizing ability up to 2.5 mm, in agreement with theoretical predictions. Details include the design of the transducers and electronics, as well as the mechanical positioner, signal processing algorithms, and complete computer program listing.

From abstract: The material included in this report is intended for a short course on electromagnetic compatibility/interference (EMC/EMI) metrology to be offered jointly by the staff of the Fields Characterization Group (723.03) and the Interference Characterization Group (723.04) of the Electromagnetic Fields Division (723). The purpose of this short course is to present a review of some of the radiated EMC/EMI measurement methods, to which the National Bureau of Standards (NBS) at Boulder, Colorado, has made significant contributions during the past two decades.

From introduction: Simple, precise expressions for lunar diameter, average brightness temperature, flux density, and shape factor are presented. An analysis of the relationship between these parameters and corresponding errors are included. For broadbeam (HPBW>d) antennas, results show that flux density and shape factor can be determined with errors less than 13 percent and 0.4 percent respectively at frequencies below 10 GHz. Extension of the analysis to higher frequencies is indicated.

Abstract: The preliminary design and testing of a planar circuit six-port with diode detectors is described. The planar circuit medium was chosen to be finline, and all preliminary work was done in WR-42 waveguide (18-26.5 GHz). The finline substrate was alumina, and initially commercial beam-lead diodes were bonded to the finline metalization. The goal is to design an integrated circuit which could be fabricated on one chip (with diode detectors) and used as part of a six port network analyzer in the waveguide bands above 18 GHz. Initial designs proved to b unsatisfactory because of high losses and reflections. Most of the problems have b en solved, and a usable integrated finline circuit is a good possibility for a millimeter wave six-port.

Abstract: Results of a research program to develop fitness-for-service criteria for assessing the significance of fatigue cracks in offshore structures are presented in five papers. Each paper describes the goals and approaches to a specific task and details the results of the study.

From abstract: The thermophysical and transport properties of selected fluids have been programmed in FORTRAN 77 which is available for micro computers. The input variables are any two of P, p, T (pressure, density, and temperature) in the single phase regions, and either P or T for the saturated liquid or vapor states. The output is pressure, density, temperature, internal energy, enthalpy, entropy, specific heat capacities (Cp and Cv), speed of sound and, in most cases, viscosity, thermal conductivity and dielectric constant.

From preface: STARPAC documentation is being published as a series of Technical Notes. This Note is the first in the series. It gives an overview of the STARPAC library, defines conventions used in the documentation, provides an example using STARPAC subroutines, and presents general background material. This Note includes information which is essential for using the STARPAC library, and users should be familiar with its contents before attempting to use any STARPAC subroutine.

Abstract: Gain and antenna parameters related to input impedance are calculated using a computer program called HVD6. This program uses well documented equations to compute these parameters for gain-standard antennas used in relative-gain or gain-transfer measurements at frequencies below 1000 MHz. The utility of this program is that it calculates gain patterns and input impedances for linear dipoles above perfect or imperfectly conducting plane ground and in free space, and for monopoles on perfectly conducting plane ground. Examples are included to illustrate the use of the program. Uncertainties in the calculated parameters are estimated to be less than those of the measured parameters.

Abstract: In electromagnetic susceptibility testing of electronic equipment, the ideal incident field is a plane wave. To approximate this condition, a seven-element array of Yagi-Uda antennas has been constructed and tested at a frequency of 500 MHz. The element weightings are determined by a near-field synthesis technique which optimizes the uniformity of the field throughout a rectangular test volume in the near field of the array. The amplitude and phase of the electric field have been measured throughout the test volume with a short dipole probe, and the agreement with the theory is excellent.

From preface: This Note documents 16 subroutines for nonlinear least squares regression. Twelve of these compute the least squares estimates, performing either weighted or unweighted analysis with either numerically approximated or user-supplied (analytic) derivatives. The other four are user-callable subroutines for two procedures used within the estimation code: the first selects optimum step sizes for approximating the partial derivatives of the model; and the second checks the validity of a user-supplied derivative subroutine.

Abstract: The problem of measuring and characterizing complicated multiple-source, multiple-frequency electromagnetic environments is becoming more important and more difficult as electrical devices proliferate. This paper outlines three general approaches to the problem which are currently under investigation at the National Bureau of Standards. The three approaches are: 1) a statistical treatment of the spatial distribution of electromagnetic field intensities, 2) a numerical computation using a finite-difference (or lattice) form of the electromagnetic action functional, and 3) use of a directional probe to scan a volume. All three methods are still in the development stage, but each appears promising.

Abstract: An expression is developed for net power delivered to a load in terms of the indicated forward and reflected power and the system S-parameters and reflection coefficients. The dual directional coupler is treated as nonideal with power reflections assumed between all ports. The system itself is used to evaluate the major S-parameter terms in net power computation, and uncertainty in the computed power is derived from origins in the power meter readings and incompletely known S-parameters.

Introduction: A reference step-like pulse generator is described which has been developed at NBS. This generator can be used for accurately characterizing the step response of various kinds of trap ient recording equipment (oscilloscopes, waveform recorders, transient digitizers, etc.). Basic design principles are given as well as complete circuit diagrams and descriptions. An analysis of the output stage of the generator is presented together with the circuit models for developing a time-domain computer simulation program using extended- SCEPTRE. Preliminary specifications indicate that the NBS Reference Flat Pulse Generator provides a negative-going reference transition duration (90 to 10 percent) of 600 ps, *20 percent with baseline perturbations of less than *2 percent for less than 5 ns.

From introduction: The purpose of this Technical Note is to describe refracted-ray scanning in detail, to analyze it as a measurement system, to document a particular system for implementing it, and to show some exemplary results.

Forward: The purpose of this report is to summarize the results obtained from a brief investigation of supercritical fluid extraction principles and applications. This study was one portion of a project funded by the U.S. Department of Energy, Office of Fossil Energy, contract nuriber DE-AI01076PR06010, in response to a preliminary proposal submitted by the authors. This report sometimes uses company trade naries to identify processes and patent holders. This usage implies no endorsement by HBS. Note also that some figures reproduced from other sources do not conform with NBS policy concerning SI units.

Abstract: Site attenuation is a measure of performance of an open test site used at frequencies below about 1 GHz for antenna calibration and equipment emission and susceptibility testing. These sites typically consist of a large, obstruction-free ground plane and the hemisphere above it. Site attenuation of an ideal site is calculated and compared to data measured using the 30 m by 60 m NBS ground screen.

Introduction: Small aperture theory is used to investigate the dual TEM cell. Analyzing coupling through an empty versus a loaded aperture leads to a model of dual TEM cell shielding effectiveness measurements. Small obstacle scattering yields results for both the field perturbation and the change in a cell's transmission line characteristics due to the presence of a test object in a TEM cell. In each case, theoretical values are compared to experimental data.

Abstract: Electroexplosive devices (EEDs) are electrically fired explosive initiators used in a wide variety of applications. The nature of most of these applications requires that the devices function with near certainty when required and remain inactive otherwise. Recent concern with pulsed electromagnetic interference (EMI) and nuclear electromagnetic pulse (EMP) made apparent the lack of methodology for assessing EED vulnerability. A new and rigorous approach for characterizing EED firing levels is developed in the context of statistical linear models and is demonstrated in this paper. We combine statistical theory and methodology with thermodynamic modeling to determine the probability that an EED, of a particular type, fires when excited by a pulse of a given width and amplitude. The results can be applied to any type of EED for which the hot-wire explosive binder does not melt below the firing temperature. Included are methods.for assessing model validity and for obtaining probability plots, called "Firing Likelihood Plots". A method of measuring the thermal time constant of an EED is given. This parameter is necessary to evaluate the effect of a train of pulses. These statistical methods are both more general and more efficient than previous methods for EED assessment. The results provide information …