Spectrum Engineering Reports

Abstract: NTIA/ITS has developed an improved electromagnetic compatibility (EMC) analysis method that can be applied to more accurately model real scenarios for evaluating interference. The methodology described in this report can be used to conduct EMC analyses for base stations that use a variety of antennas. The model can be used to determine the received power in the proximity of the base station at both the fundamental and harmonic frequencies. It uses accurate radio-wave propagation models and antenna models.

Abstract: The total radio frequency (RF) field strength is the sum of all signals incident at a given location. These signals can originate from many directions and have various polarizations. This complicates the measurement of the total RF field since commonly used antennas (dipoles, whips, etc.) respond to signals coming from a specific direction and with a specific polarization. This paper describes a prototype antenna constructed from three crossed dipole elements.

Abstract: This report describes one of three free-field radio frequency (RF) measurement systems that are currently being developed by engineers at the Institute for Telecommunication Sciences (NTIA/ITS). The objective is to provide estimates of the electrical properties of the ground (permittivity and conductivity) over which the measurement systems are deployed. This measurement system uses transmission loss measurements between two monopoles placed close to the ground at specific separation distances.

Abstract: In early 2009, the Federal Aviation Administration (FAA) became aware of interference to Terminal Doppler Weather Radars (TDWRs) that operate in the 5600–5650 MHz band and provide measurements of gust fronts, windshear, microbursts, and other weather hazards for improved safety of operations in and around airports.

Abstract: When radiofrequency pulse envelopes are observed away from their fundamental frequency their shapes differ from those at their fundamental frequency. Off-fundamental pulse envelopes tend to exhibit spikes at their rising and falling edges with lower-amplitude energy between the spikes. This phenomenon, called the rabbit ears effect, is described in this NTIA Report. Examples of rabbit ears pulse envelopes are provided in a mathematical simulation and from measurements of off-fundamental pulse envelopes of two models of 5 GHz weather radars.

Abstract: Measured power levels for radio frequency (RF) pulses that are frequency modulated (chirped) vary as a function of the bandwidth in which the measurement is performed; if chirped pulses cause RF interference, the power levels of the pulses in victim receivers will likewise vary as a function of receiver bandwidth. This report provides both heuristic and rigorous derivations of the relationships among chirped pulse parameters and the measured peak and average power levels of chirped pulses as a function of measurement bandwidth.

Abstract: We provide detailed descriptions of recent measurements conducted by the National Telecommunications and Information Administration Institute for Telecommunication Sciences in Boulder, Colorado. ITS engineers performed a comprehensive series of both conducted and radiated emission measurements of the Shore-Line-intrusion-Monitoring System (SLiMS). The SLiMS system is currently being developed by Time Domain® under the sponsorship of the Naval Facilities Engineering Command.

Abstract: This report describes speech intelligibility testing conducted on the Adaptive Multi-Rate (AMR) speech coder in several different environments simulating emergency response conditions and especially fireground conditions. The intelligibility testing protocol was the Modified Rhyme Test (MRT). Conditions included background noises of various types, as well as a mask associated with a self-contained breathing apparatus. Analog FM radio transmission and Project 25 digital radio transmission were also included in the test as reference points.

Nicholas DeMinco, Paul M. McKenna, Robert T. Johnk, Chriss A. Hammerschmidt, J. Wayde Allen, Linh P. Vu

Abstract: This report describes a modified rhyme test (MRT) conducted to characterize the behavior of digital and analog communication in the presence of background noise and moderate RF channel degradation. This is done through the use of reference systems to provide a manufacturer-independent perspective on this issue.