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 41 for “"varactor"”.
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Switching characteristics of the varactor-diode parametron
Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering, 1960
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The design and realization of higher order varactor frequency multipliers.
Massachusetts Institute of Technology. Dept. of Electrical Engineering. Thesis. 1967. M.S.
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EFFECTS OF GATE THICKNESS, GATE MORPHOLOGY, AND EMISSIVE MATERIAL ON ORGANIC LIGHT EMITTING VARACTOR CAPACITOR PERFORMANCE
… must be invented. Organic light emitting varactors (OLEVs) represent a promising future in this regard and are explored here. OLEVs are built similarly to OLEDs, with an added gate. Under AC driving, this gate allows control of current flow to yield a higher maximum efficiency than the …
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Hydrothermal Processing of Barium Strontium Titanate Composites on Printed Circuit Board for Thin Film Varactor Applications
Thin film Ba0.7Sr0.3TiO3 has been deposited onto printed circuit boards at low temperatures for low and high frequency applications. The fabrication method involves spin coating sol-gel composites (a mixture of BST powder suspended in an amorphous BST sol), and treating the resultant films at …
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A Post-Fabrication Tuning Method for a Varactor-Tuned Microstrip Filter using the Space Mapping Technique
… the tuning voltages of a fabricated 4-pole varactor diode tuned microstrip combline filter with a center frequency of 1 GHz and an absolute bandwidth of 200 MHz is presented. In the proposed application, implicit space mapping is exploited to map the circuit based coarse model and the …
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Design and analysis of an electrically small inductively loaded sector antenna for frequency reconfiguration using varactor diodes
… design for frequency reconfiguration using varactor diodes placed in inductive loads. In order to allow for frequency agility, a DC bias network is carefully designed utilizing blocking capacitors to allow for an impedance match over the bands of interest. Characterization of the antenna on …
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Tunable Impedance Matching Network Fundamental Limits and Pracitical Considerations
… transmission line characteristic impedance and varactor range. Equations to predict loss due to varactor quality factor are demonstrated and the ability of parasitics to both increase and decrease <em>TR</em> are shown. Measured results exemplify i) the potential to develop matching networks …
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Modelling and applications of MOS varactors for high-speed CMOS clock and data recovery
… and characterization of a special type of varactor, the accumulation-mode MOS varactor, used in the tank circuit as a tuning component of these types of VCOs. We propose a new sub-circuit model for this type of varactor, which can be easily migrated to other technologies as long as an …
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An investigation of solid state high level upconverters using hybrid computing techniques
… all solid state microwave radio relay links. A varactor diode is normally employed as the frequency mixing element providing the high microwave efficiencies essential in this application with large conversion gains and power handling capacity. This thesis presents the derivation of a hybrid …
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Electronically tuned 23 GHz Gunn oscillators for a microwave datalink
… The dissertation presents the development of the varactor controlled Gunn oscillators that constitute the crystal locked microwave sources of the radio. An accurate description of a design procedure for Gunn oscillators at 23 GHz is presented. With reference to advanced modulation methods which …
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Reconfigurable microstrip antennas with tunable radiation pattern characteristics
… driven patch. A tuning mechanism with the aid of Varactor diodes is introduced for the parasitic patch that effectively allows for controlling its electrical size. This (these) reconfigurable parasitic patch (es) is (are) then applied in different fashions to devise several antenna designs with …
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Design and analysis of pattern null reconfigurable antennas
… This dissertation develops a compact, varactor-loaded NRA that circumvents these limitations, providing measured continuous null steering up to 31 degrees off broadside at 2.42 GHz along the E plane within its common impedance bandwidth. In addition, careful consideration of the modes …
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Millimeter-Wave and Sub-Terahertz Parametric Harmonic Generation
… of symmetric antiparallel pair of series varactors to achieve about 24-dB conversion loss (CL), −8-dBm maximum output power (POUT), and 18% relative bandwidth (BW). Two reconfigurable frequency multipliers (RFMs) are designed based on antiparallel nMOS-varactor pairs (APNVP) and …
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A Fully Monolithic 2.5 GHz LC Voltage Controlled Oscillator in 0.35 μm CMOS Technology
… design of an "inversion-mode" MOS (I-MOS) tuning varactor is presented, along with a discussion of the effects of varactor nonlinearity on VCO performance. I-MOS varactors are shown to have substantially improved tuning range (and tuning curve linearity) over conventional MOS varactors. Practical …
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The design and realisation of electronically tunable dielectric resonator microstrip filters
… These tuning configurations incorporating GaAs varactor diodes have been investigated to determine a circuit which greatly perturbs the DR fundamental mode. The amount of tuning that can be obtained by these methods exceeds more than 60MHz of the unperturbed value of resonant frequency with …
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Integrated Tunable LC Higher-Order Microwave Filters for Interference Mitigation
… parallel synthesis of BPF. A practical switched varactor control scheme is proposed for large tuning ratio varactors to reduce the nonlinear contribution from the varactor substantially which improves the tunable LC BPF filter linearity. Second, parallel addition and subtraction techniques were …
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A 5-6 Ghz Silicon-Germanium Vco With Tunable Polyphase Outputs
… is -115.5 dBc/Hz at a 1 MHz offset and a tank varactor control voltage of 1.0 V. The VCO figure-of-merit (FOM) for the symmetric inductor VCO is -179.2 dBc/Hz, which is within 4 dBc/Hz of the best reported VCO in the 5 GHz frequency regime. The die area including pads for the symmetric inductor …
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Finite difference time domain analysis of microstrip antenna-circuit modules
… tuneable microstrip patch antennas using varactor diodes were also studied. Tuning range and harmonic radiation were demonstrated. Single and dual device Gunn oscillator antennas were analysed and their radiation patterns were calculated for the first time. All of our results were in …
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Off-resonance and detuned surface coils for B₁ inhomogeneity in 7-Tesla MRI
… in frequency by changing the voltage across a varactor diode, or detuned using a resonant detuning circuit. It was discovered that with a 1 cm spacing and a surface coil tuned just above resonance, SNR near the surface coil could be improved by upwards of 400%, with the trade-off of a reduced …
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Lithium niobate RF-MEMS oscillators for IoT, 5G and beyond
… a binary-weighted digital capacitor bank and a varactor that are both connected in series to the resonator. The measured best phase noise performances of the VCMO are -72 and -153 dBc/Hz at 1 kHz and 10 MHz offsets from 178.23 and 175.83 MHz carriers, respectively. The VCMO consumes a direct …
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