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As the next-generation communications technology continues to evolve to utilize millimeter-wave frequencies, calibration methods are needed for the nonidealities related to these frequencies in communications electronics. In this article, we demonstrate a 1-GHz bandwidth, 64-quadrature-amplitude-modulated signal source at 92.4-GHz carrier frequency with relative phase and magnitude that may be made traceable to primary standards. By using predistortion techniques, we are able to repeatably obtain a nominal error vector magnitude (EVM) of 1.4%. In addition, we track correlated and uncorrelated uncertainties using a Monte Carlo method to show the distribution of uncertainty of the EVM measurement with the 5th and 95th percentiles at 1.5% and 3.1%, respectively. We examine the dependence of the EVM in the traceable source on digital-to-analog converters’ imbalance and system drift over time. Finally, we use the stable, low-EVM signal to ascertain EVM degradation on- and off-axis in a stationary over-the-air setup. [ABSTRACT FROM AUTHOR]

When reverberation chambers are loaded to increase the coherence bandwidth for modulated-signal measurements, a secondary effect is decreased spatial uniformity. We show that an appropriate choice of stirring sequence, consisting of a combination of mode-stirring mechanisms such as paddle and antenna-platform stirring, can mitigate the potential for increased uncertainty. We develop a new mode-stirring sample correlation model for uncertainty due to the stirring sequence. In a comparison with an empirical uncertainty analysis, the model is found to have an agreement within 2.5%. Our analysis is demonstrated for four loading cases in each of three reverberation chambers. The model is used to determine an optimal stirring sequence for a given chamber setup directly from correlations associated with each stirring mechanism. The model can also be understood in terms of the entropy of a measurement and it is shown that maximizing the entropy corresponds to a minimized uncertainty. The method presented here not only provides insight into sources of uncertainty but also allows users to determine an optimal mode-stirring sequence with minimized uncertainty for a given chamber setup. [ABSTRACT FROM AUTHOR]

We assess the potential error in measurements of the power transfer function corresponding to a reverberation chamber set-up when different antenna types are used for the reference and device-under-test measurements. We derive a mathematical description of the transfer function that accounts for differences in the amount of unstirred energy, represented by the spatially averaged K factor, arising from various antenna types. Our results show that loaded chamber configurations, combined with reference/device antenna pairs having significantly different radiation patterns, can result in statistically significant errors in the prediction of the transfer function. If it is possible to obtain an estimate of the K factor associated with the device antenna, this correction can improve the estimate of the transfer function that would be experienced by the device under test. Finally, we develop a method that could be used in standardized test methods to bound the uncertainty associated with the unknown K factor for common antenna types. [ABSTRACT FROM PUBLISHER]

In less than a decade since the mainstreaming of cellular wireless technology, spectrum has become saturated by data-intensive smartphones, driving the so-called spectrum crunch. As a solution, the wireless community is pursuing the use of alternatives to current wireless technologies, including multiple-input/multipleoutput (MIMO) antenna arrays that allow increased simultaneous transmission capacity; the millimeter-wave (mmW) spectrum (30-300 GHz) to alleviate the spectrum crunch in current frequency bands; and ultradense networks transmitting wide-band modulated signals to allow short-range, high-speed data transfer. [ABSTRACT FROM PUBLISHER]

Reverberation chambers provide a repeatable test environment for laboratory over-the-air testing and represent a viable solution for testing large-form-factor wireless devices. Such tests often involve “imperfect chamber” configurations in which the chamber is loaded with RF absorbing material. We provide step-by-step guidance on configuring and verifying chamber performance for over-the-air tests of single-antenna cellular wireless devices. We illustrate these methods with numerous examples, highlighting the tradeoffs in various chamber configurations. We conclude by calculating total radiated power and total isotropic sensitivity for a cellular-enabled wireless router and discuss methods for assessing uncertainty in estimates of these quantities. [ABSTRACT FROM AUTHOR]

The nondestructive assay (NDA) of plutonium-bearing materials using gamma-ray spectroscopy supports global nuclear nonproliferation and safeguards efforts. High-purity germanium (HPGe) detectors have been used for this application for decades, but the uncertainty limit remains around 1% relative error for measured isotope ratios, an order of magnitude larger than destructive assay. To lower NDA uncertainty limits, we are pursuing new measurement technology using superconducting microcalorimeter detectors, and assessing the sources of current uncertainty limits. We compare results from analysis of plutonium isotopic standards using HPGe and microcalorimeter detectors, and find lower random error for the microcalorimeter data. Uncertainties in the reference values of constants of nature contribute to the total measurement error. For one particular set of constants, the gamma-ray energies, we find that microcalorimeter analysis is much less sensitive (more than a factor of ten) to the uncertainty in nuclear data than HPGe. [ABSTRACT FROM PUBLISHER]

Microcalorimeter detectors provide unprecedented energy resolution for gamma-ray spectroscopy. One application is measuring the isotopic composition of plutonium-bearing samples by non-destructive gamma-ray spectroscopy to support nuclear safeguards and nonproliferation efforts. When measured with conventional high-purity germanium (HPGe) detectors, data from these samples contain significant peak overlaps requiring spectral deconvolution for analysis. The improved energy resolution of the microcalorimeter detector reduces peak overlaps leading to improvement in the statistical error component of the total measurement uncertainty. In this paper, we describe analysis code that was developed for spectral peak fitting and isotopic content determination from microcalorimeter and HPGe data. We apply the code to data collected from several plutonium standards to quantify the improvement of the statistical error derived from the improved energy resolution. [ABSTRACT FROM PUBLISHER]

GEANT4 is a versatile Monte Carlo code for simulating the interactions of radiation with matter. GEANT4 has proven to be an effective toolkit for the simulation of a wide variety of detectors. We are interested in the application of GEANT4 to a new type of sensor technology being developed for X-ray and gamma-ray measurements. Microcalorimeter detectors based on transition-edge sensors coupled to bulk absorbers are an emerging technology for hard .X-ray and soft gamma-ray measurements with unprecedented energy resolution. In this work, we assess the ability of the GEANT4 electromagnetic physics package to reproduce measured microcalorimeter data. We also use the simulations to explore the design space of absorber materials and cryostat design. [ABSTRACT FROM AUTHOR]

Gamma-ray spectrometry systems based on High-Purity Germanium (HPGe) have been the long-standing leader in terms of resolution since their introduction many years ago. The application of this technology to the spectroscopic assay of special nuclear material led to the development of several isotopic analysis tools, including the advanced software package FRAM, which was, and continues to be, developed at Los Alamos National Laboratory. Although FRAM can be applied over a wide range of energies, the significantly higher intensity of the x-ray region in the neighborhood of 100 keV makes analysis of this area of the spectrum advantageous, especially in the case of plutonium. However, even with HPGe, the multitude of gamma-ray and x-ray peaks that exist in the 100-keV region are sufficiently convoluted so as to preclude determination of plutonium isotopic composition without the introduction of some error. The novel technology of cryogenic microcalorimeter detectors, shown to have an order of magnitude better spectral resolution than HPGe, has recently opened new doors with respect to these difficulties. Now, for the first time, the powerful capabilities of FRAM have been paired with the unparalleled resolution of microcalorimetry in the analysis of plutonium spectra. Preliminary results of these analyses, as well as an outlook for future measurements, heretofore unobtainable with HPGe, will be presented. [ABSTRACT FROM AUTHOR]