• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1040-1049
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• 2006

A design method for minimizing transmission loss of a broadband right-angle transition from a coaxial cable to a microstrip line is presented. The right-angle transition has been widely used where printed circuit applications need to be fed from behind the ground plane using coaxial line. To obtain the minimized transmission loss over the whole operating frequency range of the transition, design parameters such as ground aperture and probe diameters, ground aperture offset, and stub length are optimized using a commercial electromagnetic simulation software. Results are presented for the optimum right-angle transition from an SMA connector to a microstrip line on common reinforced 0.787 mm thick PTFE substrates. Measurements of a fabricated transition show that reflection coefficient is less than -22 dB and insertion loss is less than 0.45 dB over $0.05{\sim}20GHz$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.10
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• pp.971-981
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• 2002

An open-ended coaxial probe method has been considered as one of effective tools for measuring electrical properties of its contacted material without shaping and fitting. The measured reflection coefficient at the probe's end is able to convert into the corresponding complex permittivity by employing the improved version of virtual transmission-line model Presented by our lab already. But the error of complex permittivity converted by equivalent model increases as the operating frequency ascends high. The errors of complex permittivity in the open-ended coaxial probe can be yielded compositively by the imperfect contact or probe, manufacture error of probe and complex permittivity error of reference material etc. Therefore it is necessary to limit the problem to identify the error causes in high frequency. In this paper, the errors which are resulted from the measurement of reflection coefficient are removed by using the FDTD(Finite-Difference Time-Domain) method, the error causes are limited the conversion model problem. And the error study of the improved conversion model is performed from several viewpoints. At first, the local minimum of parameter to be calculated by the iteration method in the conversion model is checked. At second, the modeling of the equivalent model is checked in the frequency range. From this study, we know the valid range of the improved conversion model.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.339-342
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• 1998

The stacked microstrip patch antenna is modeled by a simple cavity model. Using this model, the input impedance of the stacked microstrip patch antenna fed by a coaxial probe is expressed as a function of antenna paprameters and frequency. We calculate the input impedance of the stacked microstrip patch antenna for the variation of frequency.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.310-313
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• 2003

Complex permittivities of human head simulating liquids were measured by a sample holder of terminated slotted coaxial line with a movable probe at mobile communication frequencies. The validity of the liquid measurement system was checked by experiments with the reference liquids. Liquids of ingredients for human brain suggested in IEEE draft and those made by the authors were measured by this slotted line system.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.212-213
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• 2002

전자기기의 소형화에 동반하여 동작주파수가 높아짐에 따라 여기에 이용되는 소자의 크기도 밀리 사이즈에서 마이크로 사이즈까지 작아지고 있다. 이에 따라 여기에 이용되는 각종 소자의 전기적인 값도 작아지고 있으며 허용 오차 값이 적은 정밀한 소자가 이용되고 있다. 그러나 소자의 크기와 소자값의 감소에 따라 정확하고 간편하게 그리고 많은 소자를 효율적으로 측정할 수 있는 방법이 필요하다. 특성 임피던스 50 $\Omega$을 가지는 동축선로형 프루브 제작에 대해 이미 검토하였다[1]. (중략)

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.139-142
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• 2004

X-band Waveguide slot way antenna is developed for heliborne MTD radar applications. The antenna is composed of multi-layer waveguide structures. Each of them has it's own functions, such as, radiation, power/phase distribution, coupling, etc. Broad-wall offset slots are used for radiators, inclined slots on broad-wall for power distribution to radiating(branch) waveguide, some kind of coaxial probe structures for in-phase coupling and H-plane T-junction power dividers. Antenna is realized by precision machining and careful assembly. It is tested and measured by 3m${\times}$l.7m planar near-field probe, which is set-up in MTG. Far-field calculations have good agreement in tolerable bounds. Special but necessary process such as brazing, will increase the accuracy and performance. Results show promising possibilities of future applications for real systems.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1972-1974
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• 2000

In this paper, we made an experiment on fault location of underground cables with travelling wave. The 5C2V coaxial cables of 100, 200m length, connected with discharge gap, are used for simplifying model cable lines of power cable. And 100KHz -2MHz CT and HV probe are installed at one side of the ends. We made travelling pulse in discharge gab and then pulse travelled along the cable to the both ends. Therefore, it is detected in CT and HV probe. Measuring the time difference of the pulse start and arrival, we were able to obtain the distance of pulse travelling. Consequently, our experimental results show the possibility to detect fault location of underground cables with travelling wave.

• Smart Structures and Systems
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• v.7 no.4
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• pp.319-328
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• 2011

In this study, the measurements of the dielectric constants of soil at 900 MHz and 1 GHz were made to relate those properties to the moisture content of the soil. This study's intention was to use the relationship between the dielectric constant and the moisture content to develop a landslide prediction system. By monitoring the change of the moisture content within the soil using ground penetrating radar (GPR) systems in the field, the possibility of a landslide is expected to be detected. To establish a database for the dielectric constants and the moisture content, the measurements of soil samples were made using both an open-ended dielectric coaxial probe and the GPR. Based on the measurement results, correlations between the GPR and reflector for each frequency at 900 MHz and 1 GHz were found for the dielectric constants and the moisture content. Finally, the mechanism of the measurement device to be implemented in the field is suggested.

• 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.416-422
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• 2006

In this paper, we have designed and favricated the high gain and wideband microstrip patch antenna including IEEE 802.11a. To widen the bandwidth of microstrip antenna, firstly we have used the microstrip line-coaxial probe feeding method and inserted a U-slot in the rectangular patch. Secondly, to improve the antenna gain, we have used a $2{\times}2$ array structure. From the measured results, wideband characteristics of 1 GHz bandwidth($5.110{\sim}6.142$ GHz) for VSWR<2 was obtained. The measured eain was 13 dBi in both the E-plane and H-plane at the frequency of 5.15 GHz, 5.35 GHz, 5.50 GHz, and 5.85 GHz.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.541-547
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• 2000

Experiments were done for the comparison of performance and flow characteristics between a two stage axial flow fan and a counter-rotating axial flow fm. The fan performance curves were obtained by the Korean Standard Testing Methods for Turbo Fans and Blowers (KS B 6311). The fan flow characteristics were measured using a five-hole probe by the non-nulling method. Each stage of the two stage axial flow fan used for the present study has an eight bladed rotor and thirteen stator blades. The front and the rear rotor of the counter-rotating axial flow fan have eight blades each and are driven by coaxial counter rotating shafts through a gear box located between the rear rotor and the electric motor. Both of the two axial fan configurations use identical rotor blades and the same operating conditions for the one-to-one comparison of the two. Performance characteristics of the two configurations were obtained and compared by varying the blade setting angles and axial gaps between the blade rows. The passage flow fields between the hub and tip of the fans were measured and analyzed for the particular operating conditions of peak efficiency, minimum and maximum pressure coefficients.