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.
Results
Showing 1 to 13 of 13 for “"Varactor diode"”.
-
Switching characteristics of the varactor-diode parametron
Thesis: M.S., Massachusetts Institute of Technology, Department of Electrical Engineering, 1960
-
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 …
-
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 …
-
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 …
-
Design and Implementation of Radio Frequency Power Feeding Networks for Antenna Array Applications: Simulation and Measurements of Multiport, Equal and Unequal, Fixed and Reconfigurable Radio Frequency Power Feeding Networks for Narrow and Ultra-Wideband Applications
… by tuning the quarter wave transformer using one varactor diode. The power divider was applied to improve a full duplex system cancellation performance at the receiver element caused by interference from in-site transmitting antennas. This study investigated fixed power dividers, multi-output …
-
EMI measurement and modeling techniques for complex electronic circuits and modules
… radio frequency interference studies by using a varactor diode providing the required capacitance and the parasitic inductance of a magnetic field loop (i.e., a parallel LC circuit). Measurement results showed good agreement with the simulated results.</p> <p>In the third paper, a wideband …
-
Design and Implementation of Reconfigurable and MIMO Antennas for Future Heterogeneous Wireless Systems
… by means of active electronic elements including varactor diode or PIN diode with extra circuitry. The main objective of this research is to design and investigate low-profile antennas for heterogeneous wireless systems using the antenna reconfigurability concept through tuning and/or using the …
-
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 …
-
Planar groove gap waveguides
… network can be applied to the cavity using a varactor diode to vary the resonant frequency of the cavity. This is done without bridging wire and concentric etched rings as a direct result of the DC isolation of the PGGWG. A tuning range of 4.5% is achieved in measurement. From the experiments …
-
Miniaturised and reconfigurable planar filters for ultra-wideband applications
… investigated in this thesis: discrete (e.g. PIN diode, Optical switch) and continuous (e.g. varactor diode). Using the equivalent circuits and considering the direct coupled filter structure in most cases, several topologies with attractive features are developed for future communication systems. …
-
Design of New, Compact and Efficient Microstrip Filters for 5G Wireless Communications
… reconfigurable filters are designed using varactor and PIN diodes for 4G and 5G. The proposed filters are tunable in the range from 2.5 to 3.8 GHz. The bandwidth is adjustable between 40 and 140 MHz with return losses between 17 to 30 dB and insertion loss of around 1 dB. Also, the thesis …
-
Design of New, Compact and Efficient Microstrip Filters for 5G Wireless Communications
… reconfigurable filters are designed using varactor and PIN diodes for 4G and 5G. The proposed filters are tunable in the range from 2.5 to 3.8 GHz. The bandwidth is adjustable between 40 and 140 MHz with return losses between 17 to 30 dB and insertion loss of around 1 dB. Also, the thesis …
-
Design and modelling of beam steering antenna array for mobile and wireless applications using optimisation algorithms. Simulation and measrement of switch and phase shifter for beam steering antenna array by applying reactive loading and time modulated switching techniques, optimised using genetic algorithms and particle swarm methods.
… its viability. Then two hybrid coupled PIN diode phase shifters, using Branchline and Rat-Race ring coupler structures, were designed and tested. The generation of four distinct phase shifts was implemented and studied. The variations of the scattering parameters were found to be realistic, …