• Korean Journal of Optics and Photonics
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• v.25 no.3
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• pp.150-154
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• 2014

The conditions under which a composite retarder consisting of two different retardation plates can be operated as a tunable quarter-wave plate are derived. The explicit expressions for the azimuthal angle of a linear polarizer and those of two retardation plates to generate circularly polarized light are presented as a function of retardation angles. Those expressions for the azimuthal angles derived using the Jones matrix formalism are verified as identical to the expressions derived from the analysis of the trajectory on a Poincar$\acute{e}$ sphere. A couple of examples are presented for generating circularly polarized light when two identical retardation plates are used.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.823-830
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• 2010

This paper deals with a coaxial-to-waveguide transition generating circularly polarized wave to be connected with horn antennas. By combining vertical coaxial fed structure, back-short and the polarization twisting structure, the circular polarization is successfully generated in the waveguide. The designed and implemented transition shows that the present structure can significantly reduce the size of the antenna part at X-band.

• ETRI Journal
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• v.40 no.5
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• pp.561-569
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• 2018

Modern communication systems employ wideband antennas with circular polarization (CP) radiation. In this work, asymmetric modified bow-tie (ABT) and symmetric modified bow-tie (SBT) slotted circularly polarized single-point probe-fed circular patch antennas with dimensions of $40mm{\times}40mm$ for wideband applications are proposed. A 10 dB RL bandwidth of 350 MHz with CP, 3 dB axial ratio (AR) bandwidth of 100 MHz, peak gain of 4.9 dBic, and 10 dB RL bandwidth of 530 MHz with CP, 3 dB AR bandwidth of 140 MHz, peak gain of 5 dBic are obtained for ABT and SBT slotted circular patch antennas, respectively. The proposed SBT slotted patch is scaled up and down to $50mm{\times}50mm$ and $30mm{\times}30mm$, respectively. The proposed scaled-up version offers 10 dB RL and 3 dB AR bandwidths of 340 MHz and 80 MHz, with a peak gain of 5 dBic. The scaled-down version offers 10 dB RL and 3 dB AR bandwidths of 710 MHz and 180 MHz, with a peak gain of 5.25 dBic. These prototypes are suitable to work in IEEE 802.11a WLAN, ISM, and IEEE 802.11ac applications. The measured and simulated results are then discussed and compared.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1139-1146
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• 2000

In this paper, circular-polarized dipole antenna with a novel structure is designed, simulated and fabricated for PCS or IMT-2000 base station at an arbitrary test frequency(1.575 GHz). Its radiation pattern is analyzed by means of physical optics(PO). The designed antenna is made up of a horizontal and a vertical dipole elements at a height of λ/4 above an reflector. One of λ/4 length vertical dipole element is located at a height of λ/8 above an reflector. In this case, circularly polarized radiation pattern is obtained by making impedance difference due to adjusting the length of each element. The characteristic of antenna measured from this study is that return loss is 18.4 dB, -10 dB bandwidth is 360 MHz(22.8%), 2 dB axial ratio bandwidth is 30 MHz, -3 dB beamwidth is 76$^{\circ}$, 2 dB axial ratio beamwidth is 58$^{\circ}$, axial ratio is 1.7 dB at 1.575 GHz. Radiation pattern is in well agreement with the result of PO.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.5
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• pp.459-467
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• 2010

A new type of circularly polarized(CP) antenna that is characterized by having both low-profile and greater axial-ratio bandwidth(ARBW) beyond existing antennas is introduced through analysis of artificial magnetic conductor(AMC) polarizer, and experimentally demonstrated. Although it is made use of a linear-polarized dipole antenna with close proximity to ground plane, it is backed by AMC polarizer so as to efficiently radiate with circularly changed polarization whose ARBW is determined by the texture geometry, whereas existing antennas exhibit CP surface-current on radiators, which limit ARBW. The mechanism of the polarization conversion is theoretically analyzed for ARBW, and the experimental properties including the impedance matching, CP radiation pattern, axial-ratio pattern, ARBW, and two-port isolation are discussed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1537-1543
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• 2010

This paper describes a compact microstrip antenna with dual polarization characteristics. The antenna, receiving both a left-hand circularly polarized(LHCP) wave and a right-hand circularly polarized(RHCP) wave, can be used for a polarization diversity. A diamond-shaped patch with internal empty room is designed for impedance matching as well as size reduction. And slots are added around feeding point to improve input matching. The proposed antenna has been applied to GPS(global positioning system), operating at 1.57GHz. And, the proposed idea has been verified and estimated by simulation. The measurement results show that it has VSWR 2:1 bandwidth of 83MHz, 3dB axial bandwidth of about 58MHz, 3dB beamwidth of 90degree, and gain of 0dBi, respectively, for RHCP. Also, it has similar performances for LHCP.

• Journal of the Institute of Convergence Signal Processing
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• v.16 no.4
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• pp.156-161
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• 2015

In this paper, a dual-polarized multi-band multi-layer antenna for a vehicle, which operates in the GPS, bluetooth, and DSRC bands, was implemented. The antenna was designed as a multi-layer structure, and a FR4-epoxy substrate with =4.4 and =1.6mm was used. GPS and DSRC antennas have circular polarized characteristics, and a single probe feeding method was applied. Simulated results by Ansys HFSS v11 was compared with the measured ones. The size of the optimally designed antenna is $67mm{\times}67mm{\times}4.8mm$, -10dB bandwidth of the anatenna was measured to be 820MHz, 127MHz, and 862MHz in each band, and 3dB AR bandwidth of the antenna was simulated to be 19MHz and 110MHz in GPS and DSRC bands. The results confirmed that suggested system satisfies the system requirements.

• Journal of electromagnetic engineering and science
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• v.18 no.4
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• pp.267-269
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• 2018

In this letter, the null steering of a circular array is presented using a modified array factor (AF) for a global positioning system (GPS) anti-jam. The seven radiating elements were designed using a mu-zero resonance (MZR) circularly polarized (CP) antenna arranged toward the center. Since the radiating elements, which are arranged toward the center, have a CP characteristic, the AF of the seven radiating elements has to be modified considering the rotation angle of the nth radiating element. The phases of input ports can be calculated to implement a nulling of radiation patterns where the modified AF is zero. To verify the modified AF for null steering in the desired direction, two cases of power dividers operating in $L_2$ band (1.2276 GHz) were fabricated to achieve pattern nulling at a certain angle. The modified AF can be confirmed by a comparing the simulated and measured radiation patterns.

• Journal of Astronomy and Space Sciences
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• v.26 no.3
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• pp.345-354
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• 2009

A stepped septum polarizer has been designed and fabricated for the 43 GHz band KVN receiver system. The dual-circular polarizer converts left and right hand circularly polarized signals into linear polarizations in two separated rectangular waveguides. Measurements show that the performance of the designed septum polarizer covering 42-48 GHz frequency band is adequate to meet the requirement of KVN receivers. Especially, a polarizer for the KVN receiver of 85-95 GHz frequency band can be fabricated by scaling the dimensions of the septum polarizer developed in this paper.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.119-123
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• 2000

This paper described a design for microstrip antenna with EMC cross dipole for circular polarization. To realize the wide bandwidth and circular polarization, the elertromagnetic-coupled cross dipole are used. The calculated axial ratio is about 0.1 dB in the main bean direction at 12 GHz and the circular polarization is realized.