Full Anechoic Chamber Research Articles

Fractal based wire antenna impedance simulation by the method of moments

Koch curve based dipole antennas have been built up, have been simulated and measured to examine the reachable size reduction.The simulations have been performed by the method of moments (MoM) and the results have been checked by the finite element method (FEM) and by measurements. The Pocklington’ integral equation has been implemented in MATLAB environment to simulate the input impedance of dipole antennas. The ATW EFIE method has been implemented and solved by the 4NEC2 software to examine the behavior of arbitrary shaped thin wire antennas. In COMSOL Multiphysics software environment a finite element model has been set up to solve the Helmholtz equation and to simulate the antennas under examination. Koch curve based dipole antennas have been measured in a full anechoic chamber, as well and finally the numerical and the experimental results have been compared.

Analytical Solutions for the Radiated Emission of Parallel Microstrip Traces

A closed-form expression of the unintentional electromagnetic radiation of parallel microstrip traces is proposed. Based on transmission line theory, far-field Green's function, and concept of array factor in antenna theory, analytical solutions for the electric field radiated from a pair of parallel microstrip lines are developed. Depending on the printed circuit board material, dimension parameters, and termination impedances, the frequency and angular responses of far-field radiated emission on the upper half-plane can be analyzed by the presented method. The differential- and common-mode radiated emission solutions are validated by a full-wave simulator and test board measurements in a full-anechoic chamber.

Open Measurements of Edge Diffraction from a Noise Barrier Scale Model

Until today, all known simulation methods for the wave phenomenon of edge diffraction are just approximations, based on either Geometrical Acoustics or the numerical solving of the wave equation. Although these methods work fine for simple test scenarios and a certain frequency range, they fail to simulate the effect of diffraction in its whole complexity. This leads to false predictions especially for more complex geometries where the influence of multiple wave diffraction and sound scattering has to be taken into account as well. Consequently, huge effort is currently put into the development of improved simulation methods. Here, a basic need is an all-embracing validation of simulation results, which also includes the comparison with real-world measurements. Unfortunately, there is a lack of such data which is the reason why the Institute of Technical Acoustics (ITA), RWTH Aachen University, Germany, and the Centre for Quantifiable Quality of Service in Communication Systems (Q2S), NTNU Trondheim, Norway, have started an initiative called openMeasurements, which is aimed to be an internet platform for free acoustic measurement data of any kind, together with their respective simulation models (CAD-model, detailed information on sources and receivers, material data) and helpful tools. As initial step, various measurement series of a scaled-down model of a noise barrier were carried out. These series aim to give researches, developers, and common application users, the possibility to thoroughly test their prediction models of edge diffraction. The measurements were carried out in a full anechoic chamber and a turntable was used to rotate the scale-model during the measurements in steps of one degree. The scale-model was constructed with a changeable ground layer in order to massively influence the object's acoustical properties and, thus, create measurement datasets that considerably differ. Here, datasets for five different ground layers were obtained: 3 absorbers, 1 rigid surface and 1 self-constructed skyline-diffuser. A skyline diffuser was chosen as it is a well reproducible geometrical pattern, which enables a simulation of sound scattering in two ways: stochastic and deterministic. In this contribution, detailed information on the measurement setup is given and measurement procedures are described thoroughly. Measurement uncertainties are briefly discussed and first comparisons with simulations are presented. All measurements together with geometrical models of the scale-model (with/without diffuser), detailed information on sources and receivers, material data (absorption- and scattering coefficients) and useful Matlab tools are freely available for download ( www.openmeasurements.net ).

DVM-13 AIRFLOW INDUCED VIBRO-ACOUSTICS ANALYSIS OF HDD(Drive Mechanisms IV,Technical Program of Oral Presentations)

This paper studies airflow induced vibro-acoustics of HDD numerically and experimentally. The noise contribution from airflow is characterized and investigated through sound power measurements in a full anechoic chamber. A methodology is developed to simulate airflow induced noise for acoustic optimization of future products.

New acoustic test facility at Georgia Tech

Georgia Tech’s Integrated Acoustics Laboratory (IAL) is a state of the art research facility dedicated to the study of acoustics and vibration. The centerpiece of the laboratory is a 24 ft×24 ft×20 ft full anechoic chamber, which has been in operation since 1998. The IAL is currently expanding to include a reverberation room and hemi-anechoic chamber, designed and built by Acoustic Systems. These two chambers will be joined by an 8 ft×8 ft transmission loss opening, allowing for a detailed measurement and analysis of complex barriers. Both chambers will accommodate vehicles and similarly large structures. The reverberation room will have adequate volume for standardized absorption measurements. Each chamber will be equipped with dedicated multichannel data acquisition systems and instrumentation for the support of simultaneous research in all areas of the laboratory. The new test chambers are funded by a grant from the Ford Motor Company and are planned to be completed and fully functional by 1 January 2003.

30-1000 MHz field strength standard developed in anechoic chamber

An accurate electric field strength for the frequency range of 30 MHz to 1000 MHz has been developed in a full anechoic chamber with 1- Sigma uncertainty less than +or-1.9%. Reflection parameters of walls at frequencies below 200 MHz are evaluated experimentally, and the errors due to these waves are compensated in the standard and calibrations of the antennas.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>