• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 133
  • 27
  • 19
  • 5
  • 2
  • 2
  • 1
  • Tagged with
  • 237
  • 237
  • 64
  • 48
  • 46
  • 43
  • 41
  • 36
  • 31
  • 30
  • 29
  • 27
  • 26
  • 24
  • 23
  • 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

Numerical computation of the scattering coefficients of an inductive strip in a fin-line /

Deal, John C. January 1984 (has links) (PDF)
Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, March 1984. / Thesis advisor, Jeffrey B. Knorr. "March 1984." Description based on title screen as viewed on August 7, 2007. Includes bibliographical references (p. 176-177). Also available online.
2

High Data Rate Modulation Issues in Millimeter-Wave Metamaterials

Franson, Steven January 2007 (has links)
This dissertation examines the use of metamaterial structures in millimeter-wave communication systems. Metamaterials, which are composite structures that have electromagnetic properties not found in nature, have been an area of explosive growth in academic research, including applications such as electrically small antennas, sub-wavelength imaging, and negative phase velocity transmission lines. In this dissertation, several potential applications of metamaterials are investigated, including new ideas related to negative forces. The design of highly directive antennas and their use in high data rate communication systems are emphasized. At millimeter-wave frequencies, specifically in a frequency band around 60 GHz, there is an enormous amount of available unlicensed worldwide spectrum available for data transmission. These systems may benefit from the knowledge of metamaterials and their integration with antenna systems. Although there are many challenges with working at such high frequencies and the metamaterials themselves are inherently dispersive and lossy, it will be demonstrated that useful structures can be designed and fabricated at these frequencies. Metamaterial-based artificial magnetic conductors were designed and it has been shown that they can handle 'gigabit per second' data rates. Moreover, superstrate structures were also designed to achieve near zero-index of refraction properties and, as a result, highly directive 60 GHz antenna systems. These metamaterial superstrate-based patch antennas were built and tested successfully with actual 'gigabit per second' data rates. Design and practical fabrication challenges associated with these millimeter-wave applications were addressed and will be reviewed.
3

Analysis and design of millimetre wave antenna array power combines / by Ninh T. Duong.

Ninh T. Duong January 1998 (has links)
Bibliography: p. 343-355. / xxiv, 355 p. : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Based on a comprehensive review of past techniques and power combining structures, a class of spatial power combiners compatible with the requirements of millimetre wave operation are identified. / Thesis (Ph.D.)--University of Adelaide, Dept. of Electrical and Electronic Engineering, 1999?
4

Broadband guided microwave and millimeter wave transitions and their applications. / 宽带微波毫米波传输线转换器及其应用 / CUHK electronic theses & dissertations collection / Kuan dai wei bo hao mi bo chuan shu xian zhuan huan qi ji qi ying yong

January 2011 (has links)
Huang, Xiaobo. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 108-111). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
5

Design and development of passive millimeter-wave imaging systems

Stein, Edwin Lee, Jr. January 2009 (has links)
Thesis (M.S.)--University of Delaware, 2009. / Principal faculty advisor: Dennis W. Prather, Dept. of Electrical & Computer Engineering. Includes bibliographical references.
6

MEMS tuning and matching circuits, and millimeter wave on-wafer measurements /

Vähä-Heikkilä, Tauno. January 2006 (has links) (PDF)
Diss. Teknillinen korkeakoulu, 2006. / Myös verkkojulkaisuna.
7

Design, characterization, and fabrication of microwave and millimeter-wave antennas

Hwang, Timothy H. January 2007 (has links)
Thesis (M.E.E.)--University of Delaware, 2006. / Principal faculty advisor: Dennis W. Prather, Dept. of Electrical and Computer Engineering. Includes bibliographical references.
8

Novel Electromagnetic Structure, Circuit, and Material for Microwave Applications

Chen, Te-Chuan, Chen, Te-Chuan January 2017 (has links)
This dissertation presents the investigation of novel electromagnetic structure, circuit, and material for microwave engineering. There are four topics covered in this work: the study of a waveguide filter at W-band frequencies using electromagnetic crystal (EMXT) surfaces, the design of a dual-band amplifier with flexible frequency ratio, the analysis and testing of a compact 4:1 planar combiner with complex matching, and the investigation of a dielectric nanostructured material using a mixture of polymer and silver nanoparticles. First, a rectangular waveguide band-stop filter using electromagnetic crystal EMXT surfaces is presented. A waveguide is loaded on the top and/or the bottom walls with EMXT surface, which has a propagating band gap. An equivalent circuit is developed to model the filter behavior and to predict its stop band. A W-band prototype based on the proposed filter architecture is designed and tested. The experimental results show a rejection band centered at 97 GHz and a rejection level of 16 dB. Second, a dual-band amplifier is demonstrated with flexible frequency ratios. The proposed amplifier features novel dual-band Wilkinson power divider/combiner that allows large frequency ratios between the first and second bands (2.16 to 4.9) between the first and second operating frequencies. The stand-alone combiner has maximum potential combining efficiency of 95% and 75% at the first and second frequency bands, respectively. A 2.4 / 5.8 GHz prototype amplifier is tested to verify its dual-band functionality. Measured linear gains are 12.85 dB and 11.09 dB at the first and second frequency bands, respectively. Third, a “spatial” combiner inspired power combiner / divider for solid-state amplifier application is presented. The proposed “one-stage” combining is realized by a single port tapered to an oversized microstrip connecting to parallel multiport microstrip sections. Uniform amplitude/phase and complex impedance matching at the parallel multiport microstrips are simultaneously achieved by adjusting the geometry of the structure. A prototype 5 GHz 1-to-4 divider/combiner designed using ADS co-simulation is characterized. The measured combining efficiency of 82.4% is achieved at 5 GHz. Lastly, a nanostructure thin film with giant dielectric response is proposed by strategically dispersing silver nano-particles inside a Tropropylene glycol diacrylate (TRPGDA) polymer. The dielectric properties of the proposed thin film are experimentally extracted at the microwave frequencies. The measurement sample is prepared by laying a coplanar waveguide (CPW) line on the thin film that is supported by a glass substrate. Two-port S-parameter measurements on the CPW are performed. Dispersion mechanism due to internal inductance of the CPW line when calculating the effective dielectric constant is investigated. The extraction involves conformal mapping approximation that uses closed-form equations to calculate the dielectric constant and the loss tangent of each layer based on the effective dielectric constant and loss tangent of the entire structure. Alternatively, direct fitting technique using simulation to model the experiment is studied. The results of the two techniques are compared and discussed. The measured dielectric constant ranges from 30000 to 4600 from 1 to 20 GHz with a loss tangent of 0.55 to 1.75 from 1 to 20 GHz.
9

Development of micromachined millimeter wave modules for wireless communication systems

Li, Yuan 11 May 2010 (has links)
This research discusses the design, fabrication, integration, and characterization of micromachined millimeter-wave components and a signal source for THz multiplier source using the deep reactive ion etching technique. A wide range of advanced micromachined millimeter-wave components are proposed and fully validated with the measurement. These micromachined millimeter-wave passives include: the W-band straight and meander waveguides, W-band three-pole filter, waveguide hybrid and power divider, a novel CPW-to-waveguide transition and filter, and a novel cavity resonator for 60-GHz reconfigurable applications. The proposed THz multiplier source is a broadband 900-GHz silicon micromachined two-anode frequency tripler with the state-of-the-art performance. The research results enable the silicon micromachining technique to build low-loss and low-cost millimeter-wave components and THz signal sources.
10

STAR FORMATION IN THE RHO OPHIUCHI DARK CLOUD

Wilking, Bruce Alan January 1981 (has links)
New and sensitive millimeter-wave and near-infrared observation have been performed in the central regions of the ρ Ophiuchi dark cloud. High spatial resolution observations of the optically thin C¹⁸O emission lines are shown to be free of self-absorption. They permit the first accurate determination of the distribution of molecular gas and allow us to estimate the mass and visual extinction in the cloud. A completely sampled near-infrared survey of a 105 sq. arcmin area which encloses the region of highest visual extinction has revealed twenty objects (sixteen were previously unknown). We show that these objects are young stars embedded in the cloud. Synthesizing our new observations with existing radio and infrared data, we have made a detailed study of the energetics and star formation process within the ρ Oph cloud. This dissertation concludes that the high temperatures of the molecular gas cannot be due to collisions with warm dust. The feasibility of alternate heat sources such as cosmic-ray ionization, shocks, and the distortion of magnetic fields are discussed. We derive high star formation efficiencies (32-46%) in the centrally condensed core of the ρ Oph cloud which suggests that it is forming a bound open cluster. The most consistent interpretation of our data requires that an efficient burst of star formation has produced a relatively large (with respect to the initial mass function) population of low luminosity stars in ρ Oph within the last 3 million years. At this present rate of star formation, most of the molecular gas will be converted into stars in about 10⁷ yr. yielding a bound cluster. Unless this rate rapidly decreases with time, the duration of star formation in the (rho) Oph cluster (10 million years) will be considerably shorter than that suggested for the Pleiades cluster (175 m. y). The lack of stars in the 3-10 M(⊙) range indicates that subsequent star formation must be dominated by more massive stars if the stellar mass spectrum of the ρ Oph cluster is to resemble that of the conventional initial mass function. The youth of the ρ Oph cluster suggests that it may be the most recent episode of star formation in the Sco-Cen OB association.

Page generated in 0.0849 seconds