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A New 4 ?? 4 Rectangular Waveguide Short-Slot Coupler in 3D Printed Technology at Ku-Band
摘要： This paper presents a novel design of an eight-port directional coupler with a very compact structure and simple manufacturing, working in the Ku frequency band. One of the main goals of the design was to ease the manufacturing with a simple structure: the coupler consisted of four rectangular waveguide input ports, four rectangular waveguide output ports, and a central coupling region with only H-plane variation. A prototype was fabricated using additive manufacturing, with a combination of 3D printing and silver coating metallization. The obtained performance showed a theoretical bandwidth of 6.6% with 20 dB return loss for the input/output ports. Good agreement between simulations and measurements was obtained, validating the proposed coupler as a good trade-off for low cost 3D printing, compactness, and high performance for systems requiring a high number of ports as in phase arrays or Butler matrices.
关键词： rectangular waveguide,Riblet-type coupler,directional couplers,additive manufacturing
更新于2025-09-23 15:21:01
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Nanosecond laser ablation of the trapezoidal structures for turbomachinery applications
摘要： Correctly designed nature inspired micrometer size grooves i.e. riblets can be used to reduce drag. There exist several methods to manufacture these structures but all of them have their own problems and disadvantages, wherefore they are not perfectly suitable for all real industrial applications. Aim of this paper is to show how a short nanosecond pulse laser ablation can be applied in a micrometer size trapezoidal shape structures i.e. riblets manufacturing for a turbomachinery applications. It is shown that although the quality of the riblets, fabricated with this method, is not as good as with the best possible manufacturing methods, it is still enhancing the properties. Added to this, the processing speed is fast enough and acquisition costs of the system are economic so that method is suitable for the real industrial application. The wind tunnel studies indicate that the fabricated riblets on an airfoil reduce wall shear stress compared to a smooth airfoil without structuring.
关键词： micromachining,nanosecond laser,airfoil,riblet,microstructures,Laser ablation
更新于2025-09-12 10:27:22
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Fabrication of surfaces with reduced friction using nanosecond laser
摘要： In this paper a short i.e. nanosecond pulse laser ablation is utilized to fabricate trapezoidal shaped microstructures i.e. riblets that are known to reduce friction. They can be applied for example in turbomachinery applications to make system more economical by reducing the wall shear stress on flow surfaces. Previously, these structures have been manufactured using different methods like grinding and ultrashort pulse lasers. The methods used before have their disadvantages and therefore they cannot be utilized in all applications. By using the nanosecond pulse laser instead of the shorter pulses, it is possible to manufacture riblets with a high fabrication speed and economically. Although a quality of the nanosecond pulse laser manufactured riblets is not as good as ones fabricated with the ultrashort pulse lasers, they are still able to reduce friction in the turbomachinery application.
关键词： micromachining,tubomachinery,nanosecond laser,airfoil,riblet,laser ablation,microstructures
更新于2025-09-12 10:27:22
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Cavity model-based analysis of field propagation in a six-port Riblet-type directional coupler
摘要： A cavity model-based analysis of electric field propagation inside a six-port Riblet-type directional coupler has been presented in this paper. Though cavity modeling technique is not very new and was previously applied to different rectangular waveguide-based passive networks to find their network parameters, for the first time it has been used here to analyze the field propagation inside a six-port Riblet-type directional coupler. From the analysis, the frequency response of the network has been estimated. Since the main objective of this work is to analyze the field propagation inside a passive network, not to present another network, a six-port Riblet-type directional coupler that is already proposed in literature has been considered. The numerical analysis has been verified by comparing the scattering parameters data obtained from the cavity model analysis with CST Microwave Studio simulation data and measured data available in the literature.
关键词： Riblet-type directional coupler,cavity modeling technique,Aperture field distribution,method of moment,scattering parameters
更新于2025-09-09 09:28:46