• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1281-1292
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• 2001

Experiments were done for the comparison of performance and flow characteristics between a two -stage axial flow fan and a counter-rotating axial flow fan. Each stage of the two -stage axial flow fan used fur the present study has an eight bladed rotor and thirteen slater blades. The front and the rear rotor of the counter - rotating axial flow fan have eight blades each and are driven by coaxial counter ro latins shafts through a gearbox located between the rear rotor and the electric motor. Both of the two axial fan configurations have identical rotor blades and the same operating condition fur the one -to-one comparison of the two. Performance curves of the two configurations were obtained and compared by varying the blade pitch angles and axial gaps between the blade rows. The fan characteristic curves were obtained following the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fa n flow characteristics were measured using a five-hole probe by a non-nulling method. The velocity profiles between the hub and tip of the fans were measured and analyzed at the particular operating condition s of peak efficiency, minimum and maximum pressure coefficients. The peak efficiency of the counter-rotating axial fan was improved about 2% respectively, compared with the two stage axial fan. At the minimum pressure coefficient point of the two stage axial fan, the fan inlet flow patterns show that axial velocity highly decreased in the vicinity of the blade tip region. Also, the reverse flow took place at the blade tip.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.5
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• pp.53-59
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• 2010

There are various types of antenna fed method; coaxial probe, coupling, parasitic elements, and impedance matching. In this paper, the fed method of the proposed antenna is microstrip line type. The high frequency structure simulator (HFSS) is used to analyze the characteristics of the T-shaped microstrip antenna with various patch dimensions. In comparison with the basic microstrip antenna, this proposed T-shaped microstrip antenna with 40.38 % of patch dimensions has the optimum characteristics of resonant frequency, return loss, and radiation pattern at 2.0 GHz band.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.1
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• pp.1-8
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• 2011

In this paper, dual-feed circularly polarized microstrip patch antenna for GPS L1, GPS L2, GLONASS L1 signal was fabricated by using stacked patch. It was fed by dual coaxial probe on the patch at 50ohm impedance, and was simulated to resonate at GPS L1, GPS L2, GLONASS L1. To realize characteristics of right hand circular polarization using dual-feed stacked patch antenna and hybrid coupler for $90^{\circ}$ phase difference. Output of hybrid coupler was contacted input of Low Noise Amplifier(LNA). The LNA using dual band pass filter was designed and fabricated. The measured results of the implemented antenna is VSWR < 1.5 : 1 and the gain of 32dB(Zenith) over at GPS L1, L2, GLONASS L1.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12A
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• pp.1183-1187
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• 2005

In this paper, a weathercock-shaped microstrip patch antenna for application in 5.25GHz band wireless LAN is designed and fabricated. To obtain sufficient bandwidth in VSWR<2, the T-slot is inserted on the patch, the coaxial probe source is used. The measured result of fabricated antenna obtained 350MHz or about $7.62\%$ bandwidth in VSWR<2 referenced to the center frequency, the gain of 5.25${\~}$6.70dBi. The experimental 3-dB beam width is shown to be broad across the pass band in azimuth and elevation at $80.32^{\circ}$ and $83.88^{\circ}$, in several.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.222-227
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• 2005

The permittivity profile of PCB substrate in a wide bandwidth is obtained by applying the moment method to the reflection coefficients measured by an open-ended coaxial probe. In this paper, the relation between a reflection coefficients and the corresponding permittivity is expressed into an integral form and the reflection coefficient of PCB substrates with different thickness are calculated using the dispersive FDTD method. The simulation results assure the validity of our conversion procedure within $2.015\%$ error.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.1
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• pp.23-29
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• 1991

In order to improve the radiation characteristics of the microstrip antenna, microstrip array antenna consisting of one center patch fed by a coaxial probe and several patches directly coupled to the E-plane by microstrip line is analyzed. The equivalent circuit of the array antenna is represented by the conventional transmission line and the various parameters, such as the mdicrostrip line length, the patch length and the feed point location are calculated to improve the radiation pattern for 5-patch array antenna which has the equal patch width. The 5-patch array antenna with the radiation pattern which has low sidelobe level and narrow beam width is fabricated and then the measured results are compared with the computed values and the results of the single patch microstrip antenna too.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.379-387
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• 2000

In this paper, to transmit and receive the differently polarized wideband signals simultaneously with a single antenna system, the wideband, dual-frequency and dual-polarized(WDFDP) microstrip array antenna is proposed and designed. This antenna operates simultaneously at 14.25 GHz and 12.50 GHz. To extend to two dimensional array, microstrip feed line and coaxial probe through via-hole are used. The experimental results show that the proposed WDFDP microstrip antenna can be used in the compact portable terminals with a single antenna system and the characteristic of the resonators in this antenna produces a greatly enhanced bandwidth.

• Journal of the Korea Society of Computer and Information
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• v.27 no.1
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• pp.33-41
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• 2022

This paper describes a planar microstrip patch antenna designed on dielectric substrate. Two types of planar microstrip patch antennas are studied for the 5G wireless applications, one type is conventional microstrip structure, the other type is stacked microstrip structure fed by coaxial probe. Using electromagnetically coupling method, stacked microstrip patch antenna employing a multi-layer substrate structure was designed. The results indicate that the proposed stacked microstrip patch antenna performs well at 5G wireless service bandwith a broadband from 3.42GHz to 3.70GHz. The impedance bandwidth(VSWR≤2) is 360MHz(10.28%) from 3.42GHz to 3.78GHz. In this paper, through the designing of a stacked microstrip patch antenna, we have presented the availability for 5G wireless repeater system.

• Composites Research
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• v.20 no.3
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• pp.25-30
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• 2007

This paper describes the basic design and fabrication of smart skin antenna for phased array applications. The smart skin phased array antenna, of which radiation pattern can be electrically steerable without mechanical rotation, has to meet the both mechanical and electrical performance. The smart skin antenna is a honeycomb sandwich structure to enhance the mechanical performance such as strength, weight and so on. The example of smart skin antenna integrated with radome is designed with the resonant frequency of 5 GHz, circular polarization, 2 by 2 subarray, and a coaxial probe-fed excitation. In addition, the performance of raw microstrip patch antenna uncovered radome is investigate. The fabricated smart skin antenna shows a reasonable performance with gain of 12.2 dBi and frequency bandwidth of 6.4 %.

• Carbon letters
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• v.24
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• pp.62-72
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• 2017

The aim of this work was to evaluate the dielectric properties of impregnated and activated palm kernel shells (PKSs) samples using two activating agents, potassium carbonate ($K_2CO_3$) and sodium hydroxide (NaOH), at three impregnation ratios. The materials were characterized by moisture content, carbon content, ash content, thermal profile and functional groups. The dielectric properties were examined using an open-ended coaxial probe method at various microwave frequencies (1-6 GHz) and temperatures (25, 35, and $45^{\circ}C$). The results show that the dielectric properties varied with frequency, temperature, moisture content, carbon content and mass ratio of the ionic solids. PKSK1.75 (PKS impregnated with $K_2CO_3$ at a mass ratio of 1.75) and PKSN1.5 (PKS impregnated with NaOH at a mass ratio of 1.5) exhibited a high loss tangent ($tan{\delta}$) indicating the effectiveness of these materials to be heated by microwaves. $K_2CO_3$ and NaOH can act as a microwave absorber to enhance the efficiency of microwave heating for low loss PKSs. Materials with a high moisture content exhibit a high loss tangent but low penetration depth. The interplay of multiple operating frequencies is suggested to promote better microwave heating by considering the changes in the materials characteristics.