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New protocols related to Internet-of-things applications may introduce previously unnoticed measurement effects in reverberation chambers (RCs) due to the narrowband nature of these protocols. Such technologies also require less loading to meet the coherence-bandwidth conditions, which may lead to higher variations, hence uncertainties, across the channel. In this work, we extend a previous study of uncertainty in NB-IoT and CAT-M1 device measurements in RCs by providing, for the first time, a comprehensive uncertainty analysis of the components related to the reference and DUT measurements. By use of a significance test, we show that certain components of uncertainty become more dominant for such narrowband protocols, and cannot be considered as negligible, as in current standardized test methods. We show that the uncertainty, if not accounted for by using the extended formulation, will be greatly overestimated and could lead to non-compliance to standards. [ABSTRACT FROM AUTHOR]

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]

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]