• Journal of Advanced Navigation Technology
• /
• v.23 no.4
• /
• pp.309-315
• /
• 2019

This paper proposes an implementation of unequal power divider with 1:3 and 1:4 splitting ratio in multi-section structure using CPW and offset coupled transmission line. The power divider consists of a multi-section transmission line and a circuit with parallel capacitors and resistors. A multi-section transmission line was implemented by decomposing a ${\lambda}/4$ single transmission line terminated by an arbitrary impedance and converging it with a multi-section transmission line shorter than $90^{\circ}$ electrical length, and RC parallel circuits were connected between transmission lines to obtain reflection coefficient of output port and isolation characteristics between the output port. In this way, it was confirmed that the transmission lines at the unequal power divider designed at 2 GHz were shorter than ${\lambda}/4$ and implemented at least 27% less than the conventional ones, and that the broadband characteristics could be obtained.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.2
• /
• pp.131-139
• /
• 2011

In this paper, we propose a double-faced window printed antenna for aircraft applications. The proposed antenna structure consists of a feeding line and a multi-loop radiator located on different sides of the window to use the limited given-area effectively. The proposed antenna is optimized by the genetic algorithm in conjunction with the FEKO EM simulator. The optimized antenna is built and installed on a 1/10 sized KUH-Surion mock-up and antenna performances such as the reflection coefficient and the radiation patterns are measured. The optimized antenna shows a half power matching bandwidth of about 33 % at 60 MHz and an average bore-sight gain of about -3.49 dBi. To verify the reception capability of the optimized antenna, we simulated the received power according to a flight scenario. The result confirms that the optimized antenna shows a minimum received power level above -60 dBm at a range of 200 km, which is similar to the pole antenna that is currently used as a FM voice antenna for KUH-Surion.

• Journal of electromagnetic engineering and science
• /
• v.12 no.4
• /
• pp.254-259
• /
• 2012

This paper presents a closely spaced two-element folded-dipole-driven quasi-Yagi array with low mutual coupling between adjacent elements. The antenna utilizes a T-junction power divider as the feeding network, with an input impedance of $50{\Omega}$. A microstrip-stub is added to the ground plane in the middle of the two elements to improve the mutual coupling characteristics. The folded dipole driver is connected to a $50{\Omega}$ microstrip line via a broadband microstrip-to-coplanar stripline transition with a quarter radial stub. A mutual coupling of less than -22 dB is measured between two folded-dipole-driven quasi-Yagi antennas with a center-to-center spacing of 30 mm ($0.55{\lambda}_0$ at 5.5 GHz). The proposed quasi-Yagi array yields a measured bandwidth of 4.75~6.43 GHz for the -10 dB reflection coefficient and a gain of 6.14~7.12 dBi within the bandwidth range.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.54 no.7
• /
• pp.308-314
• /
• 2005

The 2 GHz film bulk acoustic wave resonator(FBAR), one of the most necessary device of the next generation mobile communication system, consisted of solidly mounted resonator(SMR) structure using Brags reflector, was researched in this paper The FBAR applied SiO$_{2}$ and W had large difference of the acoustic impedance to reflector Al to electrode and ZnO to piezoelectric layer. Specially, the FBAR applied the two-step deposition method to improve the c-axis orientation and increase reproducibility of the fabrication device had good performance. The electrical properties of plasma such as impedance, resistance, reactance, $V_{pp},\;I{pp}$, VSWR and phase difference of voltage and current, was analyzed and measured by RF sensor with the variable experiment process factors such as gas ratio, RF power and base vacuum level about concerning the thickness, c-axis orientation, adhesion and roughness. The FBAR device about the optimum condition resulted reflection loss(S$_{11}$) of -17 dB, resonance frequency of 1.93 GHz, electric-mechanical coefficient(k$_{eff}$) of 2.38 $\%$ and Qualify factor of 580. It was seen better qualify than the common dielectric filter at present and expected on business to the filter device of 2 GHz bandwidth with the MMIC technology.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.9
• /
• pp.833-839
• /
• 2011

This paper has suggested a technique for measuring VSWR at 1.8 GHz band for various modulated signals. By using directional coupler the power of incident and reflected wave is measured, and in order to minimize the size and cost of the measuring circuit, a SPDT(Single Pole Double Throw) switch is adopted to realize the circuit with just one detector and one A/D(Analog to Digital) converter. MCU(Micro Control Unit) is used to calculate the voltage reflection coefficient and VSWR, and the measured VSWR error has improved by approximately 0.2 with applying a simple bubble sorting algorithm to reduce the measurement error, the MCU process time and load.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.13 no.10
• /
• pp.1017-1024
• /
• 2002

In this paper, we present the analysis of radio wave propagation characteristics in curved tunnels. Tunnel propagation models are performed in two cases which are using ray-tracing method for straight tunnels and geometrical optics extension to the standard hybrid waveguide model for curved ones. By regression analysis for measured power based on distance between the transmitter and the received antenna in tunnels that have 3.5 m $\times$ 6 m cross section and limited wall depth path loss are 0.19 dB/m for straight section and 0.68 dB/m for curved ones. By comparing model analysis with measurement in tunnels, it has been shown that the simulated results of tunnel propagation models are similar to the measured values.

• Journal of electromagnetic engineering and science
• /
• v.6 no.1
• /
• pp.36-46
• /
• 2006

In this paper, we present a two-element circularly-polarized antenna array for UHF-band RFID reader applications. The antenna element in the array is a comer-truncated rectangular patch placed on a thick plastic-foam dielectric. The patch is fed on one of its edges by a microstrip line printed on a separate thin substrate. The array antenna is fed by a microstrip power divider. Parametric studies on the patch are carried out, from which an optimum design of a single antenna element is derived. The element spacing and the feed network of the array are investigated. A commercial electromagnetic software is employed in the analysis and design of the antenna. The designed array is fabricated and tested. Measurements show good performance characteristics of the fabricated antenna: a 11.2-dBi gain, a reflection coefficient of - 14 dB, an axial ratio less than 3 dB over 3-dB beamwidths of 40 and 60 degrees on two principal planes.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.30 no.4
• /
• pp.180-190
• /
• 2018

The preliminary study was carried out to utilize the rolling porous pendulum plate as a hybrid system combining blocking and extracting of wave energy. The Galerkin method suggested by Porter and Evans (1995) was used to solve the diffraction and radiation problems to obtain reflection and transmission coefficient, roll displacement, extracted power. The Galerkin method provides better convergence than the matched eigenfunction expansion method (MEEM), which improves the accuracy of the analytical solution even if the CPU time is shorter. The porous plate can not be said to be more effective than the impermeable plate in terms of wave energy extraction and wave blocking, but it has the advantage of reducing the wave load and exchanging seawater.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.3
• /
• pp.450-456
• /
• 2016

STDR (sequence time domain reflectometry) to detect a cable fault using a pseudo noise sequence as a reference signal, and time correlation analysis between the reference signal and reflection signal is robust to noisy environments and can detect intermittent faults including open faults and short circuits. On the other hand, if the distance of the fault location is far away or the fault type is a soft fault, attenuation of the reflected signal becomes larger; hence the correlation coefficient in the STDR becomes smaller, which makes fault detection difficult and the measurement error larger. In addition, automation of the fault location by detection of phase and peak value becomes difficult. Therefore, to improve the cable fault detection of a conventional STDR, this paper proposes the algorithm in that the peak value of the correlation coefficient of the reference signal is detected, and a peak value of the correlation coefficient of the reflected signal is then detected after removing the reference signal. The performance of the proposed method was validated experimentally in low-voltage power cables. The performance evaluation showed that the proposed method can identify whether a fault occurred more accurately and can track the fault locations better than conventional STDR despite the signal attenuation. In addition, there was no error of an automatic fault type and its location by the detection of the phase and peak value through the elimination of the reference signal and normalization of the correlation coefficient.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.42 no.1
• /
• pp.39-45
• /
• 2005

As a basic research for the development of a non-invasive blood glucose sensor using millimeter waves, we have presented a method for measuring the dielectric properties of high loss dielectrics, based on the reflection method, and investigated the variation of the dielectric properties of glucose-water and glucose -0.9% NaCl solutions in the 10～90 GHz range. In the proposed method, a minimal reflection condition is formed by placing a specially-chosen low-loss plane-parallel plate in front of a high-loss medium under test at a given frequency range. Using the minimal power reflection coefficient and the corresponding frequency at this condition, tile dielectric properties of the medium can be determined. The measured results on pure water have shown the adequacy of the proposed method. The measured results on glucose-water and glucose -0.9% NaCl solutions in the 10～90 GHz range showed that the variations of the dielectric properties of glucose solutions according to the change of their glucose concentration were maximum in the 30～45 GHz range. From these facts we concluded that the variation of about 3 mole/L in the glucose solutions must be distinguished With the measurement accuracies of ±0.1 dB and ±0.01 GHz.