Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 36 for “"Ka-band"”.
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A Ka-band free-electron laser amplifier
Thesis: M.S., Massachusetts Institute of Technology, Department of Physics, 1991
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Orthogonally coded MIMO array for Ka-band (26.5 - 40 GHz) millimeter-wave imaging
… array of transmitters and receivers operating at Ka-band (26.5 — 40 GHz), which are capable of irradiating a sample under test (SUT) using multiple transmitters simultaneously while allowing it to decode the power from each transmitter-receiver combination. The system was built, calibrated, tested …
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Study of fade and inter-fade durations in Ku- and Ka- band frequencies using OLYMPUS satellite beacons
Fade and inter-fade duration data obtained from the three beacons at 12, 20, and 30 GHz aboard the OLYMPUS satellite were analyzed. The different types of signal impairments and their causes were highlighted and a literature survey conducted. Twelve months of fade and inter-fade data were analyzed …
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System Design of an Integrated Terrestrial-Satellite Communications Network for Disaster Recovery
… Distribution Service (LMDS) system and a Ka-band satellite system, and potentially being able to provide as an additional Ka-band satellite network backbone to the Virginia Tech terrestrial LMDS system for better and faster communications deployments. The Spaceway satellite system's design …
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Static Metasurfaces Reflectors with Independent & Complete Control of Magnitude & Phase
… of the complex reflectance. Designed in the Ka band with no lumped elements required. The UC design is examined and demonstrated in several different surfaces, such as a multi-beam steering surface, capable of directing two different beams of different relative magnitudes and also having …
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Parametric Yield and Tolerance Optimisation of Electromagnetic Devices using Feature-based Non-Linear Partial Least Squares Polynomial Chaos Expansion Surrogates
… with 93 geometrical variables and an 18-variable KA band ridge waveguide filter terminated with a Vivaldi antenna. This allows for accurate yield and sensitivity estimates using 24 and 100 high-fidelity samples, respectively. Compared to Monte Carlo analysis, a minimum of 300 frequency sweeps are …
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Development of Direct Ion -Implanted Gallium Arsenide MESFET and Low-Actuation-Voltage RF MEM Switches
… justify the readiness of this technology in Ka-band and V-band applications. The low operation-voltage switches will facilitate the direct integration with current MMICs and provide a solution to broadband reconfigurable circuits. The mature GaAs MESFET technology integrated with RF MEM …
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Laboratory Measurements of the Millimeter Wavelength Opacity of Phosphine (PH3) and Ammonia (NH3) Under Simulated Conditions for the Cassini-Saturn Encounter
… and refractivity of phosphine and ammonia at Ka-band (32-40 GHz) and W-band (94 GHz), under conditions characteristic of the atmosphere of Saturn. The results were used to verify the accuracy of the phosphine formalism created by Hoffman et. al (2001) for use at millimeter wavelengths. Based …
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Beam-Steerable and Reconfigurable Reflectarray Antennas for High Gain Space Applications
… simulations. Detailed analysis is performed for Ka-band reflectarray unit cells and verified by full-wave simulations. In addition, an approach to extract the Q factors using full-wave simulations is also presented. Lastly, a detailed study on the effects of inter-element spacing is discussed. Q …
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Microwave Transmission Measurements Using a Radiometer System
… of a Total Power Radiometer, operating at Ka-Band. The design of the Total Power Radiometer relies upon several factors including, accuracy, stability, and sensitivity. Weighing these factors leads to the design and simulation of a Total Power Radiometer with 0.1 K sensitivity. Several …
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Advancing 5G Coverage: Novel Methods for Metasurface Characterization and Leaky-Wave Antenna Reconfigurability
… design with mechanical switching is proposed. In Ka-band, a contactless excitation method enables beam-steering, benefiting communication systems with cost-effective flexibility. This approach also facilitates beam scanning, bandwidth, and polarization reconfiguration. This thesis provides …
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Modeling of In(0.49)Ga(0.51)P/GaAs Heterojunction Bipolar Transistors for ADC and MMIC Circuit Design
State-of-the-art monolithic Ka-band voltage-controlled oscillators were designed, tested and fabricated. Power output was $>$5 dBm and the phase noise was $<$90 dBc/Hz at 100 kHz. The phase noise and output power are also tested vs. the ambient temperature of the oscillator. Another design is …
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Advanced Design Methodologies and Novel Applications of Reflectarray Antennas
… discussed and compared with each other. • A broadband technique by using sub-wavelength elements is proposed and prototypes are fabricated and tested. This technique enables the reflectarray to achieve a significant bandwidth improvement with no additional cost. • Infrared reflectarrays antennas …
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Modelling of Rainfall Drop Size Distributions for Application in Fade Prediction on Earth-Space Paths
… between the two. This will require operation at Ka-band where there is sufficient allocated radio bandwidth (e.g. 25.5 GHz – 27 GHz) to support the required multi-gigabit per second downlink bit rate capacity. However, at Ka-band the downlink becomes highly susceptible to disruption by rain …
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Micromachined microwave filters
… filters, three of them were designed for the X-band, and one of them was designed for the Ka band. The application of the coaxial transmission line is demonstrated with wideband and narrow band designs.
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Millimeter-wavelength remote sensing of the atmospheric structure and composition of Venus
… made of the opacity of H2SO4 vapor at W, F, and Ka Band in mixtures containing up to 3 bars of CO2 at temperatures ranging from 535-585 K, simulating the conditions of the lower atmosphere of Venus. The results of these measurements and prior laboratory studies at microwave frequencies have been …
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A Radiation Reconfigurable Magnetic Line Source Antenna: Modeling, Integration With RF MEMS, and Applications
… Each configuration operates within an impedance bandwidth common to both states, and the desired radiation characteristics in both states occur in the same plane (principal plane) of the antenna with the same polarization (principal polarization). A unique analytical modeling …
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Frequency scaling of rain attenuation on satellite links in the Ku/Ka-bands using OLYMPUS satellite data
… of the eventual need to exploit higher frequency bands. Most satellite communications traffic now use C-band (4-8 GHz) and Ku-band (12-18 GHz). The next approved, yet largely unused, frequency allocation for domestic use is in the K-band (18-27 GHz) to Ka-band (27-40 GHz). At these higher …
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A Roughness Correction for Aquarius Ocean Brightness Temperature Using the CONAE MicroWave Radiometer
… global sea surface salinity (SSS), using an L-band radiometer that measures ocean brightness temperature (Tb). The application of L-band radiometry to retrieve SSS is a difficult task, and therefore, precise Tb corrections are necessary to obtain accurate measurements. One of the major error …
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Synthesis, design, and fabrication techniques for reconfigurable microwave and millimeter-wave filters
… framework is developed for absorptive bandstop filters, a new class of bandstop filters which overcomes some of the limitations of traditional tunable bandstop filters caused by the use of lossy tunable resonators. This theory is used in conjunction with silicon-micromachining …
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