• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.3
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• pp.190-194
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• 2019

In this study, the beamforming characteristics of a reflector antenna, such as a phased array antenna, as a feeder have been studied. The beamforming characteristics were examined by observing the actual steering angle of the reflector according to the diameter, the F/D of the reflector, and the number of array elements of the feeder. In addition, the beamforming characteristics were verified by measurement using a reflector of 1.5 m diameter and a four-element log-periodic dipole array(LPDA).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.826-831
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• 2008

This paper presents hybrid antenna(HA) design based on shaped reflector for mobile satellite communication. HA is composed of a shaped reflector and a feeder having $1{\times}8$ linear phased array, and reflector shaping method is applied for the performance optimization with minimum aperture size. And, in the feeder design, HA has another merit to minimize the manufacturing cost by optimizing the number of element. Proposed HA is designed at Ka-band and can electrically control a beam pattern within ${\pm}3^{\circ}$ in the basic angle of $+45^{\circ}$ in elevation. This antenna is designed to meet ITU-R S.465-5 for beam pattern including side-lobe level.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.989-996
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• 2017

The proposed directional pencil beam antenna consists of a waveguide feeder with bended elliptical conductor plate feed and a parabolic curved reflector. Two rectangular apertures located at the broad wall near the end of the feed waveguide inserted from behind the reflector are located at the focus of the reflector and emit electromagnetic energy with bended elliptical conductor plate. This plate is designed to reflect electromagnetic energy primarily and to face the main reflector. The two rectangular apertures located at the waveguide end have inwardly protruding tabs for impedance matching of the antenna system, the shape of the tabs is a truncated oval. The proposed parabolic reflector antenna has a diameter of 400 mm and a focal length of 134.23 mm. The antenna gain is 33.68 dBi at the center frequency of 16.5 GHz, the beam width is $3.3^{\circ}$ and the reflection loss is -15 dB. Using the HFSS-IE, simulation results are performed to validate the proposed antennas.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.766-773
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• 2016

This paper proposes an aircraft-installed compact offset-parabolic-reflector antenna for the spinning direction-finding applications. The feeder of the reflector antenna is a LPDA antenna that has the ultra-wideband characteristics and the $45^{\circ}$ slant linear polarization. The reflector is designed to be slanted by $5^{\circ}$ in the elevation and to be small in size on the basis of the reference parabolic shape for the purpose of the high gain and mounting on the underside of aircraft fuselage. Over the ultra-wideband 20:1 bandwidth from S to Ka band, the measured average gain of the proposed antenna is 27.97 dBi, and the average half-power beam width is $4.55^{\circ}$ in the azimuth and $4.3^{\circ}$ in the elevation which is the pencil-beam radiation pattern. All the measured data are similar to the simulation results. The designed compact offset-parabolic-reflector antenna that is installed in the limited area has the ultra-wideband and high-gain characteristics. We expect that the newly designed antenna can be applied to the spinning direction-finding antenna system installed in an aircraft.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.7
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• pp.653-659
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• 2016

This paper proposes an ultra-wideband Log-Periodic Dipole Array(LPDA) antenna for the feeder of a reflector antenna to be used for airborne spinning direction-finding and detecting wideband signals. To obtain the ultra-wideband characteristics over the 20:1 bandwidth from S to Ka band, the radiation elements of the antenna were printed on a substrate and a wedge-typed dielectric supporter with robust structure was inserted between the substrates. Also, the center portion of the supporter was replaced by a styrofoam material to reduce the supporter weight. The 5-dB return loss of the designed LPDA antenna showed ultra-wideband characteristics, which are 37.57:1(1.09~40.95 GHz) in the simulation and 33.85:1(1.31~44.35 GHz) in the measurement. We achieved the required gains of 5.78 dBi in the simulation and 5.76 dBi in the measurement in the operating band. The proposed robust, light-weight, and ultra-wideband LPDA antenna confirmed that it can be applied for airborne applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.4
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• pp.344-350
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• 2009

This paper proposes a hybrid antenna with novel beam steering scheme. The antenna have a cassegrain structure composed of two reflectors. The main reflector is designed for high gain performance using parabola curvature, and the sub-reflector is plate and can be rotated by ${\pm}3^{\circ}$. Thus proposed antenna can steer a antenna beam using the inclination of sub-reflector. A feed array composed of 20 elements is adapted as a feeder for electrical beam steering, and the antenna can be possible to steer the beam by the feed array with sub-reflector. Proposed antenna was fabricated to be operated in Ka-band(30.085$\sim$30.885 GHz) for TX and K-band(20.355$\sim$21.155 GHz), which are the operation frequencies of the Korean satellite, Mugunhwa, to provide satellite multi-media service to vehicles. By the performance test, it can be known that the antenna has minimum gain of 47 dBi for TX and 44.4 dBi for TX and can steer the beam by ${\pm}2^{\circ}$ with sub-reflector.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.109-113
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• 2015

This paper presents the study results on a dual band feed horn for the focused reflector. A coaxial waveguide structure is attractive to avoid blockage from the feeder. The inner conductor as a hollow waveguide is designed to excite TE11 of a circular waveguide for high frequency. For low frequency, the design of the outer coaxial waveguide that propagates coaxial TE11 and prevents fundamental TEM is presented. The horn size for generation of these modes results in the degradation of performance. The return loss is improved by a capacitive iris and an inductive iris The enhanced pattern symmetry by dual mode is presented. The horn design in this paper are verified through the test.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1587-1595
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• 1996

We obtained the predicted and measured results for the reflection coefficient and radiation pattern of Ka-band (20- GHz) corrugated horn, which is usually used for feeder of reflector antenna for satellite communication, using suface impedance condition. In order to predict the reture losses of corrugated horn, we analyzed propagation constant of hybrid mode in the corrugated waveguide and then obtained the total reflection coefficient using the circuti theory of multi-step transformer. We also got the radiation pattern of corrugated horn with small flare angle, considering the phase deviation and integrate transverse field on aperture. A test model of corrugated horn antenna for Ka-band designed using theory and program displayed performance and the results agree with the theoretical prediction.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.5 s.108
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• pp.461-475
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• 2006

In this paper, it is described about the tri-band mobile antenna system design to provide broadband multimedia and direct broadcasting services using goo-stationary Koreasat 3, simultaneously operated in Ka/K/Ku band. The radiating part of the antenna system with a fan beam characteristic in the elevation plane is composed of the quasi-offset dual shaped reflector and the tri-band feeder. The tri-band feeder is also composed of the Ka/K dual band feeder with the protruding dielectric rod, the circular polarizer, the ortho-mode transducer and the circular-polarized Ku band feed array. Especially, the Ka/K dual band circular polarizer was realized firstly using the comb-type structure. For fast satellite-tracking on the movement, the Ku band feed array has the structure of the $2{\times}2$ active phased array which can make electrical beams. And, the circular-polarized characteristic in the feed array was improved by $90^{\circ}$ rotating arrangement of four radiating elements polarized circularly by a $90^{\circ}$ hybrid coupler, respectively. Four beam forming channels to make electrical beams at Ku band are divided into the main beam channel and the tracking beam channel in the output, and noise temperature characteristics of each channel were analyzed on the basis of the contributions of internal sub_units. From the fabricated antenna system, the output power at $P_{1dBc}$ of Ka_Tx channel was measured more than 34.1 dBm and the measured noise figures of K/Ku_Rx channels were less than 2.4 dB and 1.5 dB, respectively, over the operating band. The radiation patterns with co- and cross-polarization in the tri-band were measured using a near-field measurement in the anechoic chamber. Especially, Ku radiation patterns were measured after correcting each initial phase of active channels with partial radiation patterns obtained from the independent excitation of each channel. The antenna gains measured in Ka/K/Ku band of the antenna system were more than 39.6 dBi, 37.5 dBi, 29.6 dBi, respectively. And, the antenna system showed good system performances such as Ka_Tx EIRP more than 43.7 dBW and K/Ku_Rx G/T more than 13.2 dB/K and 7.12 dB/K, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.502-507
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• 2013

In this paper, a circular dual mode horn with modified aperture is proposed to improve a E/H-plane radiation pattern symmetry of a conventional oversized circular dual mode horn. The proposed antenna consists of a feeding section, a mode generation section and a phase matching section which has aperture shape transition from circle to ellipse or rectangle to improve a E/H-plane radiation pattern symmetry. To compare the performances between the proposed antenna and the convenional circular dual mode horn, the conventional circular dual mode horn and the proposed circular dual mode horn with rectangular aperture are fabricated and researched at 15 GHz. The measured results show that the conventional circular dual mode horn has 3.394 dB difference while the proposed antenna has only 0.539 dB difference between E and H-plane radiation patterns within the -11 dB beamwidth($53^{\circ}$) which is required beamwidth of the feed horn for the maximum aperture efficiency where f/d ratio of reflector antenna is 1.