Chriss A. Grosvenor

Time-Domain Free-Field Measurements of the Relative Permittivity of Building Materials

Time-domain free-field measurements comprised the dielectric properties of several common building materials using dual-ridged guide antennas and 1 mtimes1 m samples placed on an optical table covered with an absorber. The samples are polycarbonate, gypsum, plywood, a brick wall, and a concrete wall. Time gating and deconvolution are used to isolate a samples front and back surfaces to obtain the measured reflection coefficients (RCs) and transmission coefficients. Theoretical reflection and transmission equations were generated from a plane-wave model. Relative permittivity is obtained by varying the parameters in the Kirkwood-Fuoss equation until a best fit between the theoretical and measured reflection and transmission coefficients is obtained.

Complex Permittivity of Planar Building Materials Measured With an Ultra-Wideband Free-Field Antenna Measurement System

Building materials are often incorporated into complex, multilayer macrostructures that are simply not amenable to measurements using coax or waveguide sample holders. In response to this, we developed an ultra-wideband (UWB) free-field measurement system. This measurement system uses a ground-plane-based system and two TEM half-horn antennas to transmit and receive the RF signal. The material samples are placed between the antennas, and reflection and transmission measurements made. Digital signal processing techniques are then applied to minimize environmental and systematic effects. The processed data are compared to a plane-wave model to extract the material properties with optimization software based on genetic algorithms.

Radio-Wave Propagation Into Large Building Structures—Part 2: Characterization of Multipath

We report on measurements that characterize multipath conditions that affect broadband wireless communications in building penetration scenarios. Measurements carried out in various large structures quantify both radio-signal attenuation and distortion (multipath) in the radio propagation channel. Our study includes measurements of the complex, wideband channel transfer function and bandpass measurements of a 20 MHz-wide, digitally modulated signal. From these, we derive the more compact metrics of time delay spread, total received power and error vector magnitude that summarize channel characteristics with a single number. We describe the experimental set-up and the measurement results for data collected in representative structures. Finally, we discuss how the combination of propagation metrics may be used to classify different propagation channel types appropriate for public-safety applications.

Measurements in Harsh RF Propagation Environments to Support Performance Evaluation of Wireless Sensor Networks

Purpose – The purpose of this paper is to describe common methods for evaluating the performance of wireless devices such as wireless sensors in harsh radio environments.Design/methodology/approach – The paper describes how measurements of real‐world propagation environments can be used to support the evaluation process, then presents representative measurement data from multipath environments where sensor networks are likely to be deployed: a fixed‐infrastructure, process‐control environment (here an oil refinery), and a heavy industrial environment (here an automotive assembly plant).Findings – Results on the characterization of multipath in the propagation channel are summarized and how these results may be used in the performance evaluation of sensor networks is discussed.Originality/value – The paper describes measurement results from environments where little open‐literature data exists on point‐to‐point propagation, specifically high‐multipath environments. These highly reflective scenarios can pre...

Free-Space Antenna Factors through the Use of Time-Domain Signal Processing

This paper demonstrates the usefulness of time- domain processing to determine free-space antenna factors (FSAF) for electromagnetic compatibility (EMC) antennas. Our procedures are explained and data are provided for frequencies from 30 MHz to 9 GHz. We investigate time gating of dense frequency packed insertion loss data obtained with an ultrawideband measurement system. These results show the advantage of time-domain gating to provide reliable results for free-space antenna factors of EMC antennas.

Electromagnetic penetration studies for three different aircraft

The National Institute of Standards and Technology has completed electromagnetic penetration studies on three different aircraft for the Federal Aviation Administration. In these studies, we measured cavity coupling characteristics between antennas placed at various angular positions around an aircraft and determined the field uniformity within these cavities with antennas placed in various compartments inside the aircraft. This paper shows how penetration varies as a function of frequency, antenna type, antenna polarization, and cavity susceptibility for three different aircraft types, a commercial airline jet, a business jet, and a composite aircraft. We also report the quality factor and time decay of fields for internal coupling between two antennas placed in the aircraft at different locations.

Wireless communications in tunnels for urban search and rescue robots

We report on propagation tests carried out in a subterranean tunnel to support improved wireless communications for urban search and rescue robots. We describe single-frequency and ultrawideband channel-characterization tests that we conducted, as well as tests of telemetry and control of a robot. We utilize propagation models of both single-frequency path loss and channel capacity to predict robot performance. These models can also be used for optimizing wireless communications in tunnels of various sizes, materials, and surface roughness.

Time-domain measurements of radiated and conducted UWB emissions

This paper summarizes results obtained from time-domain full-bandwidth emissions measurements of selected ultra wideband (UWB) transmitting devices. Brief descriptions of two NIST-developed measurement systems are provided. High-fidelity time-domain waveforms are shown, along with associated amplitude spectra for several devices. Results are shown for both conducted and radiated emissions from UWB devices.

RF Electromagnetic Penetration of the Nasa Space Shuttle Endeavour Performed with an Ultra-Wideband System

This paper summarizes a joint NIST-NASA measurement effort to thoroughly evaluate the electromagnetic penetration of the shuttle Endeavour. NASA is concerned about the effects that microwave imaging radar systems might have on critical avionics systems on its fleet of space shuttles. As part of a multifaceted effort, a portable, NIST-developed ultra-wideband measurement system was deployed at the Kennedy Space Center to evaluate electromagnetic penetration over the frequency range of 30 MHZ - 6 GHz at selected locations inside Endeavour. The measurements were performed inside a large metal hangar, which exhibited robust reverberant behavior. A combination of reverb chamber techniques and time/frequency signal processing permitted the evaluation of electromagnetic penetration at six different locations inside the orbiter.

An electric-field uniformity study of an outdoor vehicular test range

This paper describes an electric-field uniformity evaluation of an outdoor automotive antenna test range. Electric-field uniformity results are generated from accurate, full-wave electromagnetic simulations of the test range. Measured electric-field results using an ultra wideband measurement system are also presented. The simulations and measurements indicate that the turntable has a significant influence on the field uniformity.