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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Monte Carlo Stack-Up Tolerance Analysis of the Hybrid RF/Optical Antenna Edge Sensors

Hewson, Kara 01 June 2021 (has links) (PDF)
The Deep Space Network (DSN), located at the Jet Propulsion Laboratory (JPL), is developing an RF/Optical Hybrid Antenna. This antenna concept will support the reception of high-bandwidth optical deep-space communications with simultaneous support of conventional RF uplink and downlink. The optical system on the antenna consists of sixty-four hexagonal mirrors positioned to form a spherical aperture. To align the mirrors, a Position Opto-Electronic Metrology Sensor (POEMS) system is used to measure the position of each mirror relative to one another. The POEMS system consists of a sender called a collimator, which sends collimated light to the receiving component, called a quadrant diode. The purpose of this thesis is to gain insight into the required range of the POEMS system through a Monte Carlo stack-up tolerance analysis. Misalignments and tolerances may exceed current hardware capabilities of 0.3 mm. Furthermore, this thesis aims to understand the impacts of each tolerance through sensitivity analysis. The mathematical model of the mirror assembly, the Monte Carlo, and sensitivity analysis were modeled in MATLAB. The Monte Carlo analysis in this thesis takes a random value from a probability distribution of each tolerance. Then, the analysis calculates where the intersection of the representative collimator beam on its respective quadrant diode occurs. The analysis repeats this for the desired number of random stack-up of the tolerances. The maximum pointing error obtained from the Monte Carlo simulations is 6.003 mm. The tolerances which have the most considerable effect on pointing error are the decenter (which has the most significant impact), clocking, wedge, and mirror thickness. These are the tolerances to minimize if the hardware cannot be improved to meet the required range.
2

Multiband Hybrid Internal Antennas for Mobile Phones

Wu, Chih-Hsien 24 April 2008 (has links)
In this dissertation, a series of multiband hybrid mobile phone antennas, incorporating the electric-current and equivalent magnetic-current excitation mechanisms are presented. The design concept of the hybrid antenna is that the multiband operation is achieved by incorporating the resonant modes generated by the two above-mentioned excitation mechanisms. In the first and the second antenna designs, they are obtained by stacking the antennas using the electric-current and equivalent magnetic-current excitations, and both can achieve multiband operations. For the last two antenna designs, the two different excitation mechanisms can be incorporated on a single metal plate or dielectric substrate. This kind of hybrid are promising for application in bar-type and folder-type mobile phones. Besides, in order to pass some required testing criterions and analyze the environmental effects, the hybrid penta-band mobile phone antenna applied in bar-type and folder-type mobile phones is analyzed. The main topics include the speaker¡¦s effects on the antenna¡¦s performances, the analysis of user¡¦s hand and head effects, and the analysis of the hearing aid compatibility.

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