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 34 for “"cutoff frequency"”.
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Design, Fabrication, and Modeling of Indium Phosphide Double-Heterojunction Bipolar Transistors With Sub-Millimeter Wave Cutoff Frequency
… with the goal of improving device bandwidth. The cutoff frequencies of double-heterojunction transistors are extended as high as 690 GHz while maintaining an off-state breakdown voltage greater than 3 V by using the InP/GaAsSb material system with a type-II energy band alignment. Chapter 1 of this …
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Theoretical and Experimental Evaluation of Spatial Resolution in a Variable Resolution X-Ray Computed Tomography Scanner
… results showed the increase in the maximum cutoff frequency (in the detector plane) from 1.53 to 53.64 cycles per mm (cy/mm) as the scanner FOV decreased from 32 to 1 cm. The measured results supported the modeling, except for the small FOVs (below 8 cm), where the MTF could not be measured …
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Parameter estimation of a composite load model using a hybrid approach
… pseudomedian filter is created, which accepts a cutoff frequency f_c and designs a filter with 3 dB of attenuation at f_c and a stopband at 2.75f_c. A 120 Hz cutoff frequency is chosen for this work. However, even after post-processing, the measured and simulated signals are very dissimilar, …
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The effects of electronic microscanning on infrared image aliasing and spaial resolution
… is a method which can be used to reduce spatial frequency aliasing within an image by spatially oversampling the image scene. During the microscanning process, several optically dithered subimages are acquired and combined to create a larger image. The resulting image will have a higher sampling …
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Shielded Metal Waveguides with Uniform Electric Field Distributions
… electric eld region greatly and even lower the cutoff frequency which means that a smaller waveguide may operate at the same frequency as a larger waveguide.</p>
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Conductive cylindrical surface waveguides
… waveguides guide a pure low-order mode with no cutoff frequency and low distortion, while higher-order modes are quickly attenuated. In this work, we develop simulations and conduct experiments to design a large-radius surface waveguide which can be measured with existing lab equipment. …
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Fabrication and characterization of AlGaN/GaN high electron mobility transistors
… and by varying the gate width. The maximal frequency of oscillation of 64GHz and cutoff frequency of 37GHz have been measured. The influence of the different gate widths onto the device performance was studied with multi-finger HEMTs. The HEMTs on AlGaN/GaN heterostructure on sapphire …
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Experimental and theoretical study of an integrated silicon Mach-Zehnder interferometer for chemical sensing applications
… and cladding are obtained from the single-mode cutoff frequency calculated using either analytical or numerical methods. In this thesis, details of analytical calculations to determine the cutoff frequency in terms of the waveguide parameters will be presented. The method discussed here is …
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ΒΡΑΔΥΝΗ ΔΙΙΣΗΜΕΡΙΝΗ ΔΙΑΔΟΣΗ ΠΟΛΥ ΥΨΗΛΩΝ ΡΑΔΙΟΣΥΧΝΟΤΗΤΩΝ ΜΕΤΑΞΥ ΕΛΛΑΔΟΣ ΚΑΙ ΑΦΡΙΚΗΣ ΓΥΡΩ ΑΠΟ ΤΟ ΜΕΓΙΣΤΟ ΤΟΥ 21ΟΥ ΗΛΙΑΚΟΥ ΚΥΚΛΟΥ (1978-1982)
… AND POLARIZATION OF WAVES, ARRIVAL ANGLES, FREQUENCY SHIFT AND SPREADING, PROPAGATION DELAY, MULTIPATH AND FADING. THE DETAILED DESCRIPTION OF THE TEP TERMINAL STATIONS IS ALSO GIVEN. A THEORETICAL MODEL IS PRESENTED WHICH IS BASED ON THE WAVEGUIDING OF SIGNAL THROUGH DEPLETION DENSITY …
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Switch capacitor filter design aids
… of 1) increased passband ripple, 2) increased cutoff frequency, 3) increased third notch frequency, 4) increased OBR. On the basis of this comparison, it is not possible to determine if DIANA or TCAPS is the better program. However, both DIANA and TCAPS simulate SCFs far more accurately than …
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THE EFFECT OF TROPICAL CYCLONE PASSAGE ON UNDERSEA ACOUSTIC PARAMETERS IN THE EAST CHINA SEA
… include in-layer gradient, surface duct cutoff frequency, sonic layer depth, below layer gradient, deep sound channel axis, deep sound channel strength, and critical depth. Results show that all acoustic parameters, with the exception of below layer gradient, experience a response to …
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Submicron Scaling of Indium Phosphide/indium Gallium Arsenide Heterojunction Bipolar Transistors Toward Terahertz Bandwidths
… relationships between junction temperature and cutoff frequency, and the thermal resistance dependence on device size are presented. Finally, extrapolating from the characteristics measured and extracted from fabricated HBTs, obstacles to achieving THz operation are identified, and specific …
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Experimental study of a high efficiency step-tunable MW gyrotron oscillator
… beam with 99 % Gaussian beam content at each frequency while a single-disc window was implemented with over 99.5 % power transmission at both frequencies. The achieved output power in experiment was 1.1 MW at 110 GHz and 850 kW at 124.5 GHz for the design parameters of 96 kV and 40 A. At 98 kV …
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Digitally enhanced CMOS RF transmitter with integrated power amplifier
… Butterworth transmit filters with 34 MHz cutoff frequency sufficiently attenuate the aliases of the 80 MS/s digital-to-analog converters (DACs), while retaining high in-band fidelity without corrupting the predistorted signal. When a 20 MHz, 64-QAM OFDM signal with 9.6 dB peak-to-average …
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Deeply-scaled GaN high electron mobility transistors for RF applications
… still several critical issues limiting the high frequency operation of these devices. One of the key challenges is the lower-than-expected maximum current gain cutoff frequency (fT) of deeply-scaled GaN HEMTs. The fT of the short channel devices is well below both projections from maximum …
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Mathematical model of the sprint relay race.
… zero-lag Butterworth digital filter with a 1 Hz cutoff frequency. Linear velocities were calculated using finite differences. A sprinter was modelled in two ways. The first was an Exponential Model which required as input a personal best time for the 100 m race and the sprinter's maximum constant …
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Molecular Beam Epitaxy of Gallium Arsenide Antimonide-Based Ultra-High-Speed Double Heterojunction Bipolar Transistors and Light Emitting Transistors
… a high breakdown voltage BVCEO ∼ 4V. The cutoff frequency---breakdown voltage product, fT·BVCEO, of over 2000 GHz-V, is the record value for DHBTs of any material system. Incorporating graded InAs-InGaAs emitter contact layer is also shown to effectively reduce the total emitter …
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Theoretical design of photonic crystal devices for integrated optical circuits
… can also exist in constrictions and above the cutoff frequency. We discuss how to lower reflections encountered when photonic crystal waveguides are terminated, both in an experimental setup as well as in numerical simulations. We show that light can be very efficiently coupled into and out of …
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Antenna-coupled Infrared And Millimeter-wave Detectors: Fabrication, Measurement And Optimization
… radiation, with the goal of increasing the cutoff frequency to allow infrared detection. The magnitude of response of antenna-coupled bolometric detectors to infrared radiation is affected by the thermal-conduction properties of the sensor structure. Two fabrication processes were developed …
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Investigation of the baroreflex of the rat : steady state and dynamic features
… a significant increase of power in the very low frequency region (0.00195 -0.2 Hz), and a significant decrease of power in the low frequency region (0.2 - 0.6 Hz) after SAD. The dominant power change after SAD was in the very low frequency region of the blood pressure spectra. The carotid and …
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