• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.318-321
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• 2003

In this paper, path loss and delay profile characteristics are measured in the subway platform. To evaluate the fading characteristics of the measured signals, the standard deviations are computed. The standard deviation is bigger for shorter distance. The shorter the distance, the bigger the phase difference between direct wave and reflected waves according the distance, which results in heavy fading. To compute the path loss according to distance, the average values of path loss exponent(n) is evaluated. The path loss exponents measured in the subway environment for Omni-VP(omni-directional vertical polarization) antenna and CP(circular polarization) antenna are 1.418 and 1.680, respectively, which are considerably less than 2.0, the free space path loss exponent.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.533-540
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• 1999

In this paper, a microstrip antenna is designed using a rectangular patch. To find characteristics of the antenna, computer simulations of the rectangular single microstrip patch antenna are performed with changing width and feed line. And we found characteristics of RHCP using axial ratio. Through the results, we found that the Finite Difference Time Domain(FDTD) method is an effective method for designing microstrip patch antenna. According to simulation the resonant point has been found it in the frequency received from GPS satellite. And these results were in relatively good accordance with the measured values.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.215-216
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• 2006

In this paper, the antenna the with linear active phased array of $1{\times}16$ operated in DBS band was designed. The antenna was composed of sixteen radiating elements, sixteen active channels and five Wilkinson power combiners with 4-channel inputs, a digital control board and a stabilizing DC bias board. The radiating element of the array has the structure of a microstrip stack patch with a left-hand circular polarization. And, each active channel consists of a low noise ampilifier, a 3-bit digital phase shifter and a variable analog attenuator. The breadboard of linear active phased array antenna was also fabricated to test the electrical performances. The radiation patterns of the antenna were measured after correcting initial phases of each active channel in aechoic chamber. And also, the beam scanning chracteristcs of $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ were measured.

• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.278-283
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• 2014

This paper presents a theoretical approach for a modified turnstile antenna suitable for satellite communication in order to investigate the current distributions of radiators and radiation characteristics with equivalent model analysis. The proposed equivalent model is composed of an ideally horizontal dipole antenna and vertically loaded top-hat radiating elements. The required isoflux pattern with wide beamwidth has been achieved by attaching top-hat elements to the main radiators. In addition to illustrating radiation patterns, electrical performances like current distributions have been analyzed by mathematically manipulating the equations derived from the equivalent horizontal and vertical dipole model.

• ETRI Journal
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• v.36 no.6
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• pp.889-893
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• 2014

This paper presents a high-performance dual-circularly polarized feed employing a dielectric-filled circular waveguide. Novel features are incorporated in the proposed feed, such as a dielectric rod radiator for high gain and good impedance matching; dual quarter-wave chokes for low axial ratio over wide angles and for low back radiation; an integrated septum polarizer; and two end-launch-type coaxial-to-waveguide transitions. The proposed feed shows excellent performance at 5.0 GHz to 5.2 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.769-777
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• 2010

In this paper, a switchable circularly polarized microstrip patch antenna using PIN diodes and corner slots on ground plane is proposed at 2.4 GHz. The proposed antenna has a square microstrip patch and ground plane that consists of two pair of slots and PIN diodes. The electrical lengths of the slots are adjusted by using the switching characteristic of the PIN diode, so the polarization of the proposed antenna can be switchable between linear, left-handed(LH) and right-handed(RH). By separating the ground plane for the DC bias, the size reduction effect is also obtained. When the proposed antenna is operated as linear polarization, the return loss and impedance bandwidth are 15 dB, 59 MHz, and when operated as LH and RH polarization, the minimum axial ratio and 3-dB axial ratio bandwidth are 1.17 dB, 1.67 dB, 28 MHz, and 32 MHz, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.893-902
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• 2005

We propose a novel single-feed triangular patch antenna with bar-type slots for dual-band circular polarization operation. And also propose a H-type slotted triangular patch antenna to enhance the ratio of the resonance frequencies. 3 cases of desist examples with bar-type slots were investigated and also 4 cases of H-slotted antennas were investigated to meet the dual-band requirement for GPS(Global Positioning System) and DMB(Digital Multimedia Broadcasting). One suitable design example was implemented and measured. Simulation results of the design example for GPS and DMB system show that axial ratio and maximum gain are 3.80 dB, 8.85 dBi for low-band at 1.575 GHz and 2.02 dB, 8.60 dBi for high-band at 2.642 GHz, respectively. Measured results of the implemented antenna show that $S_{11}$ is -12.43 dB for low-band at 1.575 GHz and less than -18.75 dB for high-band, respectively.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.2055-2057
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• 2004

The Ku band that has been using for the satellite communication and broadcasting would be changed to K/Ka bands. The satellite system requires the antenna structure to fabricate low loss and small antenna that is able to be integrated with other Rf circuits for both Rx and Tx. So we should design it with dual feed antennas at K/Ka bands, high isolation between two different feeds and broadband circular polarization. This paper proposes the LTCC(Low Temperature Co-fired Ceramic) process for integration with other Rf circuits and the Axial mode of the helical antenna to satisfy those requirements.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.542-545
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• 2003

An microstrip array antenna is designed based on the Sierpinski equilateral triangular patch. The Sierpinski geometry is composed of 3 equilateral triangular patch and is easy to generate a circular polarization by sequential rotation array techniques. This 1${\times}$3 Sierpinski equilateral triangular patch antenna is extended to 8${\times}$8 array antenna for satellite broadcasting receptions.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1780-1785
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• 2015

In this paper, the adaptive particle swarm optimization (APSO) algorithm is employed to design a gain-enhanced antenna with a reflector for energy harvesting. We placed the reflector below the main radiating element. Its back-radiated field is reflected and added to the forward radiated field, which could increase the antenna gain. We adopt the adaptive particle swarm optimization (APSO) algorithm, which improves the speed of convergence with a high frequency solver. The result shows that performance of the optimized design successfully satisfied the design goal of the frequency band, gain and axial ratio.