Thesis (M.S. in Systems Engineering)--Naval Postgraduate School, Sept. 2004. / Thesis advisor(s): David C. Jenn. Includes bibliographical references (p. 81). Also available online.

Approved for public release; distribution is unlimited / Antennas are designed for specific system requirements such as gain, radiation pattern, bandwidth and input impedance and patterns. During this design and testing process, one of the most important steps is the measurement of its radiation pattern to define these critical parameters. Anechoic chambers are used for indoor testing purposes. Ideally they are isolated from all kinds of electromagnetic noise and have absorber coated walls inside. They also are used for radar cross-section (RCS) measurements and electromagnetic interference tests. This thesis examines the performance of the current Naval Postgraduate School anechoic chamber. Different absorbers and antenna patterns are simulated using the Urbana Wireless Toolset. It also includes a noise evaluation of the anechoic chamber. The results of this thesis can be used to guide the users of the existing chamber configuration in setting up tests and assist in any future redesign. / Lieutenant Junior Grade, Turkish Navy

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Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains viii, 116 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 68-69).

The coupled nature of vibrational energy flow in fluid filled piping systems makes its control and subsequent reduction a difficult problem. This work experimentally explores the potential of different active, passive and active/passive control methodologies for control of vibrational power flow in fluid filled pipes. Circumferential modal decomposition and measurements of vibrational power carried by individual wave types were carried out experimentally. The importance of dominant structural bending waves and the need to eliminate them in order to obtain meaningful experimental results has been demonstrated. The effectiveness of the rubber isolator in reducing structural waves has been demonstrated. Improved performance of the quarter wavelength tube and Helmholtz resonator was obtained on implementation of the rubber isolator on the experimental rig. Active control experiments using the side-branch actuator and 1/3 piezoelectric composite yielded significant dB reductions revealing their potential for practical applications. A combined active/passive approach was also implemented as part of this work. This approach yielded promising results, which proved that combining advantages of both active and passive approaches was a feasible alternative. / Master of Science

Thesis (M.S.)--Ohio University, November, 2005. / Title from PDF t.p. Includes bibliographical references (p. 111-118)

The acoustic treatment and calibration of a new anechoic system for the Virginia Tech Stability Wind Tunnel has been performed. This novel design utilizes Kevlar cloth to provide a stable flow boundary, which eliminates the need for a free jet and jet catcher. To test this concept a series of measurements were performed both to validate the reduction in overall test section noise levels and to ascertain the effect of these modifications on the test section aerodynamics. An extensive program of experiments has been conducted to examine the performance of this new hardware under a range of conditions. These include baseline experiments that reveal the aerodynamic and aeroacoustic performance of the tunnel in its original configuration, treatment of the tunnel circuit with validation of in-flow noise reduction, wind tunnel tests to examine the effect of the test section acoustic treatment, and measurements of the aerodynamic and aeroacoustic characteristics of a NACA 0012 airfoil model over a range of angles of attack and Reynolds numbers. These measurements show that acoustically treating the walls of the circuit both upstream and downstream of the test section, as well as the fan, result in an overall reduction of 5 dB depending on frequency, of the in-flow noise level. These measurements also show that the complete system provides a reduction of between 15 to 20dB depending on frequency, in the in-flow background noise level. Measurements taken both within the test section and in the adjacent chambers also show that large Kevlar windows can be used to quietly and stably contain the flow, eliminating the need for an open-jet and jet catcher system, as well as overall noise levels competitive with many other facilities. Measurements on several airfoils at various angles of attack and Reynolds number show that the interference correction for the fully anechoic configuration is approximately -22% for model with a chord length equal to half the test section height. Aerodynamic measurements with the NACA 0012 airfoil show its lift, drag and boundary layer characteristics at high Reynolds numbers are consistent with theoretical expectations. Measurements of the window deflection as well as examination of flow transpiration through the Kevlar windows were accomplished, both with and without the NACA 0012 model. These measurements, along with the interference correction data, confirm that the Kevlar windows are a stable flow boundary. / Master of Science

Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, March 2007. / Thesis Advisor(s): Andrés Larraza, Bruce C. Denardo. "March 2007." Includes bibliographical references (p. 63-64). Also available in print.

In 2014, Toyon Research Corporation donated a 6’x6’x8’ anechoic chamber to the Cal Poly EE department to advance student education in the areas of antennas and wireless communications. An anechoic chamber is a room designed to suppress electromagnetic radiation reflections so that accurate measurement of radio frequency (RF) systems such as wireless radios and antennas can take place. Despite the fact that Cal Poly already has a larger anechoic chamber, primarily used for antenna characterization, it is the purpose of this project to design, code, and equip the new chamber so that it performs at least as good, or better than, the existing chamber. Radiation pattern is a key characteristic that describes the directionality or gain of an antenna, and it is important for quantifying and qualifying how an antenna will perform as part of a wireless communication system. Radiation pattern measurement can be time consuming because it requires measuring an antenna’s transmission or reception in in all directions. In both the old and new antenna measurement systems (AMS), a vector network analyzer (VNA) measures signals transmitted between the antenna under test (AUT) and an RF field probe within the antireflective environment of the anechoic chamber. The new system synchronizes VNA measurement with the rotation of the AUT using the automation software LabVIEW and a Sunol Sciences FS-121 antenna positioner. Then, Matlab plots the data collected by LabVIEW as well as calculates useful antenna metrics including half power beam width (HPBW) and directivity. LabVIEW also makes the AMS easy to operate because of its graphical user interface. The new anechoic chamber completes measurements faster than Cal Poly’s existing chamber, with good accuracy and ease of use. The new chamber works best with smaller antennas at frequencies up to 6 GHz and beyond. Radiation patterns have good SNR, and match with simulations and measurements done in the larger chamber. However, due to its smaller size the new AMS is not a replacement for the existing larger system when testing antennas larger than 1 m or at frequencies below 2 GHz.