• Journal of Aerospace System Engineering
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• v.16 no.4
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• pp.68-76
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• 2022

The purpose of this paper was to design the cable networks for mesh reflector antennas, considering the flexibility of structures. An effective form-find methodology is proposed. The whole parts of the cable networks are described by the absolute nodal coordinate formulation. Additionally, nonlinear deformation of the cable can be obtained. The form-finding analysis of the reflector with standard configuration is performed, to validate the proposed methodology. The truss ring structure is numerically modeled using the frame elements. To consider the flexibility of the truss ring as well as the cable net structure, an iteration analysis between the truss ring and the cable net under tensional forces is also performed in the form-finding process. The finial configuration of the reflector with tensioned cable networks is demonstrated.

• Composites Research
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• v.19 no.1
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• pp.15-21
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• 2006

It is very difficult to make complex 3 dimensional curved-shape composite laminates using the advanced unidirectional composite prepregs. This study shows development process of subscale composite parabolic antenna reflector using unidirectional AS4/PEEK prepreg tapes. The AS4/PEEK thermoplastic composite materials are known to have good thermal and chemical stabilities in addition to their high specific strength and modulus. Various lamination methods were investigated through finite element analyses to make up the laminate design of the reflector. The automated fiber placement method was used to fabricate the reflector. The thermal expansion test using full-bridge strain gage circuits was done to verity the performance of the composite product.

• Journal of Aerospace System Engineering
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• v.16 no.5
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• pp.86-93
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• 2022

Generally, a deployable solar panel is used primarily to achieve sufficient power output to perform the mission. However, temperature distribution on the antenna reflector may increase due to the shading effect induced by the presence of the deployable solar panels. Appropriate thermal design is critical to minimize the thermal deformation of the mesh antenna reflector in harsh on-orbit thermal environments to ensure remote frequency (RF) performance. In this paper, we proposed a dual-surface primary reflector consisting of a mesh antenna and a flexible fabric membrane sheet. This design strategy can contribute to thermal stabilization by using a flexible solar panel on the rear side of membrane sheet to reduce the temperature distribution caused by the deployable solar panel. The effectiveness of the mesh antenna design strategy investigates through on-orbit thermal analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.1
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• pp.39-46
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• 1993

In this paper, an offset paraboloidal reflector antenna satisfied efficiency of over 60% and sidelobe envelope line of 29-25$log\theta$ was designed and manufactured for Ku-band VSAT(Very Small Aperture Terminal) antenna. The radiation patterns of experimental antenna were computed by applying the series expansion method using the Zernike polynomials. The measured patterns are in good agreement with the computed results. The Gain, efficiency, and sidelobe envelop line fairly well satisfy the design specifications except first sidelobe level.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.154-156
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• 2006

A few ten mW white LED can substitute for the indicator light source and it is required to study several watt multi-chip semiconductor light sources in order to replace the light sources for general illumination such as incandescent lights and fluorescent lanes. Since the optical technology used for several mW white LED light source uses only 30% to 52% of the light it is required to develop the design technology of optical system and lens to improve the efficiency more than 80% for insuring the high power of white LED. In this paper, we designed and fabricated new structure reflector to increase the efficiency and is easy to make high power multi-chip LED lamp.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.785-792
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• 2024

This article provides an overview of the design methodology used to develop a conceptual set of reactivity control mechanism of a micro reactor based on the U-Battery. The U-Battery is based on remote deployment and therefore it is favourable to provide a long fuel lifecycle. This is achieved by implementing a high fissile loading content, which proves challenging when considering reactivity control methods. This article follows the design methodology used to overcome these issues, with an emphasis on a new concept of a moveable moderator which utilises the size of the U-Battery as a small reduction in moderation provides a significant reduction in reactivity. The latest work on this project sees the moveable moderator investigated during a depressurised loss of forced coolant accident, where a reduction of moderator volume increases the maximum fuel temperature experienced. The overall conclusion is that the maximum fuel temperature is not significantly increased (4 K) due to the central reflector region relatively lower volumetric heat capacity compared to that of whole core. However, a small temperature increase is observed immediately after the transient due to the central reflector removal because it reaches energy equilibrium with the fuel region faster.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.171-172
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• 2007

• The Journal of Engineering Research
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• v.1 no.1
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• pp.5-14
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• 1997

The purpose of thesis is to analyze the radiation characteristics of an offset gregorian antenna in order to design the satellite-loaded antenna. In order to compute the radiation pattern of the sub-reflector, the reflected wave is obtained by GO(Geometric Optics) at an arbitrary shaped sub-reflector. Then the total radiation EM wave is obtained by summing the diffracted fields obtained by UTD(Uniform Geometrical Theory of Diffraction) and the GO fields. In order to calculate the far field radiation pattern of the main reflector, the radiation integral equation is derived from the induced current density on reflector surface using PO(Physical Optics). The kernel is expanded in terms of Jacobi-Bessel series for increasing the computational efficiency, then the modified radiation integral is represented as the double integral equation independent of observation points. When the incident fields are assumed to be x-or y-polarized field, the characteristics of radiation patterns in the gregorian antenna is analyzed in case of the main reflector having the focal length of 62.4$\lambda$, diameter of 100$\lambda$, and offset height of 75$\lambda$, and the sub-reflector having the eccentricity of 0.501, the inter focal length og 32.8$\lambda$, the horn axis angle of $9^{\circ}$ and the half aperture angle of $15.89^{\circ}$. The cross-polarized level and side lobe level in the offset geogorian reflector are reduced by 30dB and 10dB, respectively, in comparison with those of the offset parabolic antenna.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.939-940
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• 2015

In this paper, a design method for a quasi-Yagi antenna (QYA) suitable for UHF band is studied. Due to the mutual coupling between a coplanar strip (CPS)-fed planar dipole and a conducting strip director placed close to the dipole, the dipole obtains broadband characteristics. A ground reflector improves gain in the lower frequency band, and the antenna size might be reduced by employing a bent reflector. The balun between the CPS line and the microstrip(MS) line is constructed by connecting the end of MS line and the CPS line through a shorting pin. In addition, a ring-type conductor connects the CPS line and reflector. The effects of various geometrical parameters and balun on the antenna characteristics are examined. An antenna, as an design example for the proposed antenna, is designed for the operation in the frequency band of 470-806 MHz for terrestrial DTV.

• Structural Engineering and Mechanics
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• v.45 no.3
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• pp.411-422
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• 2013

A well-designed mesh shape of the cable net is of essential significance to achieve high performance of cable-network antenna reflectors. This paper is concerned with the mesh design problem for such antenna reflector structure. Two new methods for creating the topological forms of the cable net are first presented. Among those, the cyclosymmetry method is useful to generate different polygon-faceted meshes, while the topological mapping method is suitable for acquiring triangle-faceted meshes with different mesh grid densities. Then, the desired spatial paraboloidal mesh geometrical configuration in the state of static equilibrium is formed by applying a simple mesh generation approach based on the force density method. The main contribution of this study is that a general technical guide for how to create the connectivities between the nodes and members in the cable net is provided from the topological point of view. With the new idea presented in this paper, multitudes of mesh configurations with different net patterns can be sought by a certain rule rather than by empiricism, which consequently gives a valuable technical reference for the mesh design of this type of cable-network structures in the engineering.