This master's thesis is engage in suggestion of low noise 70 cm band amplifier with filter and diode attenuator. At first the thesis describes the basic parameters of amplifier, for example gain, noise figure and dynamic extent. Later in detail describes individual parts, which are the device consist of. At every part of system is mentioned the diagram of connection and values of components, which are ascertained from calculation, simulation and recommendation of producer. The characteristic parameters of amplifier were measured after construction.

Silicon carbide is a promising semiconductor material for high voltage, high frequency and high temperature devices due to its wide bandgap, high breakdown electric field strength, highly saturated drift velocity of electrons and outstanding thermal conductivity. With the aim of overcoming some challenges in metallization and doping during the fabrication of silicon carbide devices, a novel laser-based process is provided to direct metallize the surface of silicon carbide without metal deposition and dope in silicon carbide without high temperature annealing, as an alternative to the conventional ion implantation, and find applications of this laser direct write metallization and doping technique on the fabrication of diodes, endotaxial layer and embedded optical structures on silicon carbide wafers. Mathematical models have been presented for the temperature distributions in the wafer during laser irradiation to optimize laser process parameters and understand the doping and metallization mechanisms in laser irradiation process. Laser irradiation of silicon carbide in a dopant-containing ambient allows to simultaneously heating the silicon carbide surface without melting and incorporating dopant atoms into the silicon carbide lattice. The process that dopant atoms diffuse into the bulk silicon carbide by laser-induced solid phase diffusion (LISPD) can be explained by considering the laser enhanced substitutional and interstitial diffusion mechanisms. Nitrogen and Trimethyaluminum (TMA) are used as dopants to produce n-type and p-type doped silicon carbide, respectively. Two laser doping methods, i.e., internal heating doping and surface heating doping are presented in this dissertation. Deep (800 nm doped junction for internal heating doping) and shallow (200 nm and 450 nm doped junction for surface heating doping) can be fabricated by different doping methods. Two distinct diffusion regions, near-surface and far-surface regions, were identified in the dopant concentration profiles, indicating different diffusion mechanisms in these two regions. The effective diffusion coefficients of nitrogen and aluminum were determined for both regions by fitting the diffusion equation to the measured concentration profiles. The calculated diffusivities are at least 6 orders of magnitude higher than the typical values for nitrogen and aluminum, which indicate that laser doping process enhances the diffusion of dopants in silicon carbide significantly. No amorphization was observed in laser-doped samples eliminating the need for high temperature annealing. Laser direct metallization can be realized on the surface of silicon carbide by generating metal-like conductive phases due to the decomposition of silicon carbide. The ohmic property of the laser direct metallized electrodes can be dramatically improved by fabricating such electrodes on laser heavily doped SiC substrate. This laser-induced solid phase diffusion technique has been utilized to fabricate endolayers in n-type 6H-SiC substrates by carbon incorporation. X-ray energy dispersive spectroscopic analysis shows that the thickness of endolayer is about 100 nm. High resolution transmission electron microscopic images indicate that the laser endotaxy process maintains the crystalline integrity of the substrate without any amorphization. Rutherford backscattering studies also show no amorphization and evident lattice disorder occur during this laser solid phase diffusion process. The resistivity of the endolayer formed in a 1.55 omega•cm silicon carbide wafer segment was found to be 1.1E5 omega•cm which is sufficient for device fabrication and isolation. Annealing at 1000 oC for 10 min to remove hydrogen resulted in a resistivity of 9.4E4 omega•cm. Prototype silicon carbide PIN diodes have been fabricated by doping the endolayer and parent silicon carbide epilayer with aluminum using this laser-induced solid phase diffusion technique to create p-regions on the top surfaces of the substrates. Laser direct metallized contacts were also fabricated on selected PIN diodes to show the effectiveness of these contacts. The results show that the PIN diode fabricated on a 30 nm thick endolayer can block 18 V, and the breakdown voltages and the forward voltages drop at 100 A/cm2 of the diodes fabricated on 4H-SiC with homoepilayer are 420 ~ 500 V and 12.5 ~ 20 V, respectively. The laser direct metallization and doping technique can also be used to synthesize embedded optical structures, which can increase 40% reflectivity compared to the parent wafer, showing potential for the creation of optical, electro-optical, opto-electrical, sensor devices and other integrated structures that are stable in high temperature, high-pressure, corrosive environments and deep space applications.

Yes / In this paper, we present a simple reconfigurable multiband antenna with two PIN diode switches for WiMAX/WLAN applications. The antenna permits reconfigurable switching in up to ten frequency bands between 2.2 GHz and 6 GHz, with relative impedance bandwidths of around 2.5% and 8%. The proposed antenna has been simulated using CST microwave studio software and fabricated on an FR-4 substrate. It is compact, with an area of 50 × 45 mm2, and has a slotted ground substrate. Both measured and simulated return loss characteristics of the optimized antenna show that it satisfies the requirement of 2.4/5.8 GHz WLAN and 3.5 GHz WiMAX antenna applications. Moreover, there is good agreement between the measured and simulated result in terms of radiation pattern and gain. / Engineering and Physical Science Research Council through Grant EP/E022936A.

High frequency solid-state switches are critical elements in communication systems, radio frequency (RF) systems and instrumentation. Key parameters to an RF switch include insertion loss while on and off-state isolation. Power handling and linearity are important to consider for a cost-effective construction. This becomes a design challenge into K-band frequencies as components required need to be small, dielectric losses and transmission lines need to be physically matched for proper isolative and through states. This thesis presents a novel single pole eight throw (SP8T) hybrid design composed of commercially available surface mount technology solutions to achieve high isolation and low insertion loss from 2-20GHz. A range of PIN diode solutions were surveyed against key design requirements for the SP8T hybrid switch. There were no commercially available solutions for a SP8T switch using surface mount components. A SP2T switch is combined with two SP4T to make the hybrid model. A wide range of RF switch topologies were simulated and designed into a printed circuit board panel that includes 15 test structures. This board is fabricated on a low loss dielectric material with a 4-layer stack that is operational up to 20 GHz and beyond. An onboard calibration structure including STOL standards are tested through a vector network analyzer to determine losses and reflection. Each switch design is on its own board to better determine the performance of the SP8T hybrid. High frequency coplanar waveguide to 2.4mm coaxial connectors are used to evaluate each board. This design is characterized against individual MMIC and PIN diode boards through switched states in decibels (dB). Second harmonic content is also measured at a target frequency at 2.4GHz for all configurations to determine the magnitude of undesirable spectral content with input power no greater than 10dBm. Results display acceptable loss in the lower half of the frequency band and narrow resonance nearer to 20 GHz due to board loss and reflections. This design has been successful in its design and operation at broadband RF frequencies. Performance characteristics are given in the summary section. Details of the design process and measurement methodology are given in the body of this thesis.

RF/Microwave switches are widely used in microwave measurement systems, telecommunication and radar applications. The main purposes of RF switches are Tx-Rx switching, band select and switching the signal between different paths. Thus, they are key circuits especially in T/R modules. Wideband operation is an important criterion in EW applications. High power handling is also a key feature especially for radars detecting long range. In this study, different types of high power solid state switches operating at X-Band are designed, fabricated and measured. The main objectives are small size and high power handling while keeping good return loss and low insertion loss. The related studies are investigated and analyzed. Solutions for increasing the power handling are investigated, related calculations are done. Better bias conditions are also analyzed. The measurement results are compared with simulations and analysis. Circuit designs and simulations are performed using AWR&reg / and CST&reg / .

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19722号 / 工博第4177号 / 新制||工||1644(附属図書館) / 32758 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 髙岡 義寛, 教授 山田 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The purpose of this project was to design, construct, and evaluate an alpha spectrometer based on an inexpensive p-i-n photodiode as a radiation detector. The BPX-61 p-i-n photodiode was selected and calculated to have a 93 µm wide sensitive volume at 25 V reverse bias. Electronics consisting of a charge-sensitive preamplifier, a pole-zero canceling CR-(RC)4 pulse shaping amplifier, and an adjustable detector bias voltage supply were devised and assembled. Several alpha spectra were recorded from different alpha radiation sources to determine the performance of the alpha spectrometer. The results show that the alpha spectrometer could successfully and accurately measure alpha spectra, which could then be used to identify radioactive materials present in the sources. An FWHM resolution of about 230 keV was measured for 5.486 MeV alpha particles from Am-241. This resolution is inferior to most alpha spectrometers that measure under vacuum. However, because the device does not require a vacuum pump and uses USB for power and data acquisition, it is a convenient and compact option for field measurements. The low cost and reasonable performance of commercial p-i-n photodiodes as radiation detectors could be appealing for future alpha spectroscopy applications.

The objectives of this work were to investigate, design and implement beam steering antenna arrays for mobile and wireless applications using the genetic algorithm (GA) and particle swarm optimisation (PSO) techniques as optimisation design tools. Several antenna designs were implemented and tested: initially, a printed dipole antenna integrated with a duplex RF switch used for mobile base station antenna beam steering was investigated. A coplanar waveguide (CPW) to coplanar strip (CPS) transition was adopted to feed the printed dipole. A novel RF switch circuit, used to control the RF signal fed to the dipole antenna and placed directly before it, was proposed. The measured performance of the RF switch was tested and the results confirmed 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, with an acceptable ±2 phase shift tolerance. Next, antenna beam steering was achieved by implementing RF switches with ON or OFF mode functions to excite the radiating elements of the antenna array. The switching control process was implemented using a genetic algorithm (GA) method, subject to scalar and binary genes. Anti-phase feeding of radiating elements was also investigated. A ring antenna array with reflectors was modelled and analysed. An antenna of this type for mobile base stations was designed and simulation results are presented. Following this, a novel concept for simple beam steering using a uniform antenna array operated at 2.4 GHz was designed using GA. The antenna is fed by a single RF input source and the steering elements are reactively tuned by varactor diodes in series with small inductors. The beam-control procedure was derived through the use of a genetic algorithm based on adjusting the required reactance values to obtain the optimum solution as indicated by the cost function. The GA was also initially used as an optimisation tool to derive the antenna design from its specification. Finally, reactive loading and time modulated switching techniques are applied to steer the beam of a circular uniformly spaced antenna array having a source element at its centre. Genetic algorithm (GA) and particle swarm optimisation (PSO) processes calculate the optimal values of reactances loading the parasitic elements, for which the gain can be optimised in a desired direction. For time modulated switching, GA and PSO also determine the optimal on and off times of the parasitic elements for which the difference in currents induced optimises the gain and steering of the beam in a desired direction. These methods were demonstrated by investigating a vertically polarised antenna configuration. A prototype antenna was constructed and experimental results compared with the simulations. Results showed that near optimal solutions for gain optimisation, sidelobe level reduction and beam steering are achievable by utilising these methods. In addition, a simple switching process is employed to steer the beam of a horizontally polarised circular antenna array. A time modulated switching process is applied through Genetic Algorithm optimisation. Several model examples illustrate the radiation beams and the switching time process of each element in the array.

Phase shifters are common microwave circuit devices, which are widely used in telecommunication and radar applications, microwave measurement systems, and many other industrial applications. They are key circuits of T/R modules and are used to form the main beam of the electronically scanned phase array antennas. Wideband operating range is an important criterion for EW applications. Hence, wideband performance of the phase shifter is also important. In this study, four wideband phase shifter circuits are designed, fabricated and measured for 6-18 GHz frequency range. Phase shifters are separately designed in order to get 11.25, 22.5, 45 and 90&ordm / phase shifts with minimum phase error and low return losses. Phase shifter circuits are designed and fabricated in microstrip structure onto two different substrates as Rogers TMM10i and Alumina using printed circuit board and thin film production techniques, respectively. Also phase shifter circuits that include microstrip spiral inductors for DC biasing are designed and fabricated using thin film production technique. For each design the fabricated circuits are measured and results are compared with simulation results in the content of this thesis. Circuit designs and EM simulations are performed by using ADS2008&reg / , Sonnet&reg / , and CST&reg / .

Radio frequency (RF) and microwave switches are widely used in several different applications including radar, measurement systems, telecommunications, and other areas. An RF switch can control a radar’s transmit vs. receive mode, select the operating band, or direct an RF signal to different paths. In this study, a single pole eight throw (SP8T) switch using only Surface Mount (SMT) components is designed and simulated in Keysight’s Advanced Design System (ADS). Single pole eight throw is defined as one input and eight possible outputs. A star network configuration with series-shunt PIN diode switches is used to create the 8-way RF switch. There are other commercially available SP8T switches from MACOM, Skyworks, Analog Devices, and other vendors that operate around this bandwidth. However, this design uses SMT components and series-shunt diode configurations to create a device in the GHz range and power handling in the high 20 to 30 dBm range. This study modeled components in ADS, including the PIN diodes and the bias tees. The project also analyzed multiple layouts, finalizing the optimal design to meet specifications. The insertion loss, bandwidth, isolation, return loss, power handling, and switching speed are analyzed in the final design. Key specifications for this design are determined by comparing to other commercially available SP4T and SP8T switches from MACOM, Skyworks, Analog Devices, and other vendors, as well as developing an operational switch over the 2-18 GHz bandwidth. Additional specifications include limiting insertion loss to 2.0 dB maximum and maximizing isolation to 30 dB minimum. Switching speed and power handling specifications are also set to 20 ns and 23 dBm, respectively. Future projects will work on design fabrication and improvements to the manufactured switch.