1,721,004 research outputs found
Virtual Prototype of a Dielectric Window for High Power Microwave Tubes
No full textThis paper describes the Virtual Prototype of a Dielectric Window (DW) for High Power Microwave Vacuum Tubes and Linear Accelerators (LINAC). Design formulas are provided and Computer Aided Design techniques based on COMSOL Multiphysics are proposed. The virtual prototype considers the Thermo-mechanical effects due to the joule effect induced by the power which crosses the DW and the Thermal contact with the Tube connected to the device. The proposed analysis involves Electromagnetic Waves (EMW), Joule Heating and Thermal Expansion (JHTE) and Moving Mesh (MM) interfaces of COMSOL Multiphysics. In this study, we show how to compensate the thermal induced degradation of the device performances, by exploiting the consequent Thermo - mechanical deformation of the opportunely designed device shape, which modify constructively the electromagnetic (EM) fields to re-increase performances
The Squarax Amplifier: An Electromagnetic and Thermo-mechanical Innovation
No full textThis paper describes a novel broad band Spatial Power Combiner (SPC) Amplifier based on Square Coaxial (Squarax) Transmission Line (TL), able to tolerate the Thermo-Mechanical effects due to the transistor heating. In the proposed SPC, Fin Line to microstrip
transitions (FLuS) are inserted into the Squarax TL, in order to connect many Monolithic Mi-
crowave Integrated Circuit (MMIC) Solid State Power Ampli¯er (SSPA) while maintaining an
easy integration. The proposed structure has some advantages over the traditional SPC's. The
Squarax SPC geometry allows the feeding of a higher number of MMIC than in a Waveguide
SPC, and its straight pro¯le allows to connect simple and low-cost square or rectangular heat-sink devices with high thermal dissipation attitude. Conversely, coaxial SPC needs apposite circular heat-sinkers that requires expensive custom production. Squarax structure ensures high power outputs and small sizes, together with theoretical DC frequency cut-o®. In this work, a 16 cards Squarax SPC in the operative bandwidth 4{18 GHz has been designed, able to account for 32 MMIC SSPA's. The design Electromagnetic and Thermo-structural simulation of the proposed device are shown
Virtual prototyping of a microwave fin line power spatial combiner amplifier
No full textThis paper describes the Virtual Prototyping based on a COMSOL Multiphysics simulation for a novel Microwave Fin Taper (FT) Spatial Power Combiner (SPC) Amplifier.
The analyzed system is waveguide (WG) based, and uses FT Probes to convert the energy of a rectangular WG EM fundamental mode to a Microstrip Transmission Line TEM mode, in order to be amplified by a Solid State Power Amplifiers.
The power dissipation of the MMIC amplifiers produces a considerable temperature increase, stresses and strains with consequent displacement of the structures, which alter the desired behavior of the device. These multiple effects have been investigated at the same time.
The model is organized by using Thermal Stress (HT), Moving Mesh (MM) and Electromagnetic Waves (EMW) COMSOL modules.
The in-frequency behavior of the electric field and S-parameters has been computed in thermal stress operative conditions
High Efficiency Ka-Band Spatial Combiner
No full textA Ka-Band, High Efficiency, Small Size Spatial Combiner
(SPC) is proposed in this paper, which uses an
innovatively matched quadruple Fin Lines to microstrip
(FLuS) transitions. At the date of this paper and at the
Author's best knowledge no such FLuS innovative
transitions have been reported in literature before. These
transitions are inserted into a WR28 waveguide T-junction,
in order to allow the integration of 16 Monolithic
Microwave Integrated Circuit (MMIC) Solid State Power
Amplifiers (SSPA's). A computational electromagnetic
model using the finite elements method has been
implemented. A mean insertion loss of 2 dB is achieved
with a return loss better the 10 dB in the 31-37 GHz
bandwidth
Multiphysics Modeling Based Design of a Key-Holes Magnetron
No full textThis paper proposes a particular design technique of an 8 slots resonant cavities X-Band Magnetron. Such study is based on a Multiphysics (MP) simulation and consider thermalstructural effects due to the cathode heating, taking into account that electromagnetic behavior and thus device efficiency depend critically to the operating temperature and to the related thermal induced displacements of the materials. The proposed study involves Thermal Stress (TS), Eigen-frequency (EF) and Particle Tracing (PT) analysis performed with the Finite Element Method (FEM). These computations have been performed on COMSOL.
Electric field related to the main resonant modes and particle trajectories have been computed in thermo mechanical operative conditions. Magnetron working points have been estimated
Thermal and solid-mechanics FEM simulation of a microwave spatial power combiner amplifier
No full textThis paper describes the Thermal and structural combined simulation on COMSOL Multiphysics of a Microwave (MW) Fin Taper (FT) Spatial Power Combiner (SPC) Power Amplifier (PA), based on rectangular Waveguide (WG).
In the SPC based PA's, the captured power is feeded by microstrip transmission lines (μSTL’s) to Monolithic Microwave Integrated Circuit (MMIC) Solid State Power Amplifier (SSPA’s).
The power dissipation of the MMIC SSPA’s produces a considerable temperature increase and induces a thermal expansion of both the PA’s and the connected structure, which can alter its desired Electromagnetic (EM) behavior. SSPA’s are composed by driver and ended stage transistors which are been considered as different causes that contribute to the total effects, in order to estimate the reached temperatures in the different areas.
The model is organized by using Heat Transfer in solids (HT) and Solid Mechanics (SM) COMSOL modules. Temperature, stress and displacement under operative conditions have been computed
Key-Holes magnetron design and multiphysics simulation
No full textThis paper describes the design and
the characterization of an 8 slots resonant
cavities Magnetron, which undergoes the
thermal-structural effects due to the cathode
heating. The proposed study involves Thermal
Stress (TS), Eigen-frequency (EF) and Particle
Tracing (PT) analysis based on a COMSOL
Multiphysics (MP) simulation.
Magnetrons are well known and more utilized
High Power (HP) Radiofrequency (RF) Vacuum
Tube (VT) oscillators. In order to generate high
power signals, they employ thermoelectric
cathodes which can reach very high
temperatures, necessary to produce the enough
surface charge density [1].
Since device efficiency depends critically to
the operating temperature, a Multiphysics (MP)
approach has been adopted.
A PT and an EF analysis with a computation of
the power density distribution of the electric field
resonant modes and particle trajectories and
velocities have been performed, considering the
thermal-structural modifications induced by the
cathode heating to the entire structure
Multiphysics Design of a Klystron Buncher
Get PDFThe Multiphysics design of a 130 GHz klystron Buncher cavity is described in this paper. In this high frequency range, dimensions are critical and expose the device to multiple physics effects, due to the power dissipations, affecting the electromagnetic performances. The proposed device is integrated with a carbon nanotube cold cathode in order to reduce thermal expansion and an opportune airflow controls the temperature. The multiphysics design is performed on COMSOL in order to ensure the desired behavior in operative conditions. Electromagnetic fields and scattering parameters have been computed when the Buncher is subjected to multiple physics factors. The appropriate geometries and materials and can be found
Broadband TE10 to TE20 mode transformer for X band
No full textThis paper deals with a broadband TE10 to TE20 mode transformer in a WR90 rectangular waveguide with more than 35 dB suppression of the fundamental mode and only 0.4 dB of maximum transformation loss. Two fin lines are employed with appropriate configuration in order to obtain a broadband mode transformation. The proposed mode converter can be suitably employed in Spatial Power Combining amplifier to increase the number of parallel combined devices
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