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.

This thesis deals with fully anechoic chamber design. The main aim of this thesis is to design fully anechoic chamber according to acoustics laws and customers (Honeywell’s) requirements. The fully anechoic chamber will be used for measuring sound and vibration quantities. This work is divided into two main parts. The first part deals with the general anechoic chamber theory and all its related design aspects. The second part, practical part, focus on specific design according to requirements. The design of the chamber was performed using advanced design methods.

This thesis details the design and construction of an anechoic chamber for acoustic testing and measurements of large UAS propellers. Three propellers are considered, as they are common propeller designs used for large UAS today. The knowledge and practices involved with acoustic testing and measurements in anechoic chambers, as well as the results of noise studies related to large UAS, are not widely available due in large part to the limited availability and use of large UAS in the public domain. Using established principles related to fundamental acoustic theory and propeller noise, the aeroacoustic noise from large UAS propellers was measured to study and evaluate the reduction in total aerodynamic noise. This data and research provides the ability to evaluate propeller noise in relation to the overall detectability of large unmanned aircraft systems.

Small satellites are satellites that weight less than 500 kg. Compared to larger satellites, a small satellite, especially a cube satellite, has limited surface area. The limited surface area casts challenges for allocating essential parts, such as antennas, for the satellite. Therefore, antennas that are conformal to the satellite surface have distinct advantages over other types of antennas that need significant mounting area. One of the very effective conformal antennas is cavity-backed slot antennas that can be integrated around solar cells and do not compete for extra surface area. The previous study performed on cavity-backed slot antennas was mainly a feasibility study and did not address realistic concerns such as effective feeding methods for the antennas. This thesis work is aimed at providing more detailed study on achieving high quality circular polarization (CP) and simplified feed design to initiate effective integration of the antenna with solar panel. In order to accurately characterize an antenna, an effective antenna range in an anechoic chamber is important. Utah State University had an effective near-field range; however, there was not an fully shielded anechoic chamber. As another objective of this thesis work, a state-of-the-art anechoic chamber has been constructed, calibrated, and utilized to measure different antenna parameters. This thesis also shows correct methods to measure important antenna properties such as CP and antenna efficiency.

<p>This thesis aims to develop a control system for measuring electromagnetic compability (EMC). This has meant that a controller designed around an ATmega8 microcontroller has been manufactured and programmed. It has also meant the development of a comprehensive control software in the program MATLAB. The control system has been tested with satisfactory results and can now, monitor and control measurements of the EMC-type.</p> / <p>Detta examensarbete syftar till att utveckla ett styrsystem för mätning av elektromagnetisk kompabilitet (EMC). Detta har inneburit att ett styrkort uppbyggt kring en ATmega8 mikrokontroller har tillverkats och programmerats. Det har även inneburet utveckling av en övergripande kontrollmjukvara i programmet MATLAB. Styrsystemet har testats med tillfredsställande resultat och kan nu, övervaka och kontrollera mätningar av EMC-typ.</p>

This thesis aims to develop a control system for measuring electromagnetic compability (EMC). This has meant that a controller designed around an ATmega8 microcontroller has been manufactured and programmed. It has also meant the development of a comprehensive control software in the program MATLAB. The control system has been tested with satisfactory results and can now, monitor and control measurements of the EMC-type. / Detta examensarbete syftar till att utveckla ett styrsystem för mätning av elektromagnetisk kompabilitet (EMC). Detta har inneburit att ett styrkort uppbyggt kring en ATmega8 mikrokontroller har tillverkats och programmerats. Det har även inneburet utveckling av en övergripande kontrollmjukvara i programmet MATLAB. Styrsystemet har testats med tillfredsställande resultat och kan nu, övervaka och kontrollera mätningar av EMC-typ.

Today Atlas Copco Rock Drills AB hasn’t got any method to determine how many warning alarms they need on their machines and how they should be mounted to use their full potential. At the moment a travel alarm is usually placed in the front of the machine and a reverse alarm in the back. Then a measurement of the sound pressure level around the machine is performed to see if it is enough to pass the limit according to different ISO-standards. Otherwise they have to mount some extra alarms and then do the measurements again until the standards are fulfilled. The aim of this thesis work is to develop a method for determine how many alarms Atlas Copco Rock Drills AB need on the machines, and also how they should be mounted to fulfil the different criteria according to ISO-standards in the early phase of construction. From the different divisions within Atlas Copco Rock Drills AB (LHD, SDE and TME) arrived four different alarms, which are used on their machines. Sound pressure level measurements were conducted on these, in the anechoic chamber at audiological research centre at the university hospital in Örebro. In the LMS Test.Lab software a measurement sphere was built around the horns and based on the data obtained at the anechoic chamber sound directivity plots were made. Together with earlier machine measurement data from Atlas Copco Rock Drills AB, an Excel program was made constituting an example of how the horns should be mounted. LHD = Loaders and trucks/underground rock excavation SDE = Surface drilling equipment TME = Tunnelling and mining equipment / Idag har Atlas Copco Rock Drills AB inte någon metod för att bestämma hur många varningsalarm som behövs på sina maskiner samt var de ska placeras så de utnyttjar sin fulla potential. I nuläget monteras ett signalhorn vid främre delen och ett backlarm i bakre delen av maskinen. Sedan utförs en ljudtrycksmätning runt maskinen för att kontrollera om man uppfyller kraven från olika ISO-standader. Annars monteras fler alarm och mätningen utförs på nytt tills standarderna uppfylls. Detta examensarbete har som mål att ta fram en metod som bestämmer hur många alarm Atlas Copco Rock Drills AB behöver på sina maskiner, samt hur de skall placeras för att uppfylla kriterierna från olika ISO-standarder redan i konstruktionsstadiet.  Från de olika avdelningarna inom Atlas Copco Rock Drills AB (LHD, SDE och TME) mottogs fyra olika alarm, som används på maskinerna. På dessa utfördes ljudtrycksmätningar i det ekofria rummet vid audiologiskt forskningscentrum på universitetssjukhuset i Örebro. I programmet LMS Test.Lab byggdes en sfär av mätpunkter runt alarmen och baserat på insamlade data från det ekofria rummet konstruerades direktivitetsdiagram. Tillsammans med data som Atlas Copco Rock Drills AB redan hade från tidigare mätningar på maskiner gjordes ett Excel-program, som ger ett exempel på hur alarmen bör monteras. LHD = Loaders and trucks/underground rock excavation SDE = Surface drilling equipment TME = Tunnelling and mining equipment

In this study, a method to predict vehicle pass-by noise in a finite dimensioned, semi-anechoic chamber with chassis dynamometer has been developed. Vehicle noise has been modeled as the summation of the individual contributions regarding the principal noise components, namely, engine including air intake, front tire and rear tire noises. This method employs wave propagation, Doppler shift, and time delay in the estimation of the sound pressure due to each component at points of interest specified by relevant standards. An acoustical simulation model has been developed in MaTLAB environment. The model has been applied on two different vehicles. Finally, the predicted sound pressure values are found to be in good agreement with the corresponding values acquired in outdoor measurements addressed in ISO 362 for vehicle pass-by noise measurement standard.

This Master´s thesis deals with principles of determination of the sound power level. At the very beginning there is an explanation of important concepts. Afterwards there is an overview of standards that deal with the sound power level determination, including the ČSN EN ISO 9614-1 standard which is used for the experiment. Last but not least, there is described the experiment, consisting of several measurements of the same object, but every time with different configuration of measuring and sound reflective surfaces.

Master thesis examines a selected part of electromagnetic compatibility. In this work, there is theoretically discussed how electromagnetic interference appears and how is spread through free space environment. To eliminate ambient interference signals, the measurements have been performed in anechoic chamber where the undesirable interference signals were suppressed. In the thesis, there are also described parameters of EMI receivers and limits of electromagnetic interference. The description of calculations of the antenna height for finding maximum intensity of electric field strength for standard measurement distance has been made. For proposed transformed measurement distance, calculations of intensity electric field with addition of parameters measuring antenna and object under test were performed. Correction curves for conversion intensity electric field have been obtained as the result.