• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1168-1177
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• 2004

This paper presents the characteristics of the electromagnetically coupled small broadband disk-loaded monopole antenna with multiple shorting pins. The electromagnetically coupled monopole antenna can achieve broad bandwidth by controlling resonant frequency of the rectangular disk-loaded monopole and a probe with the spiral strip line monopole. The number and arrangement of the shorting pin affect the capacitance of the disk. The variation of the capacitance changes resonant frequency of the antenna, and therefore, its electrical sizes and frequency bandwidth are also affected. The antenna with three shorting pins has a volume of $0.094\lambda_0{\times}0.094\lambda_0{\times}0.094\lambda_0$ in electrical length and the frequency bandwidth of $26.8\%\;for\;VSWR\leq2$ with the center frequency at 2.556 GHz.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.30-36
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• 2005

Recently, It has been reported that the spin sprayed ferite film shows better magnetic properties at high frequeny that the ferrite by co-firing over $800^{\circ}C$ . Besides, there is no limitation to select the substrate materials because it can be processed with relatively low temperature below $100^{\circ}C$. Therefore, we fabricated film inductor as a passive device for DC-DC converter by a use of spin sprayed embedded form was completed by via hole process of pad opening. Saturation magnetization of 0.61 T and real part of permeability of 110 were obtained in Ni-Zn ferrite. In addition, inductance of 1.52 ${\mu}H$, quality factor of 24.3 at 5 MHz were measured with spiral 16 turn inductor. The rated current of inductor was 863 mA.

• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.687-692
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• 2013

This paper presents a compact power divider using microstrip-slotline transition technology. By using the microstrip-slotline transition, the ${\lambda}/4$ transmission lines of the divider can be changed to two ${\lambda}/8$ transmission lines in the multilayer structure. In the microstrip-slotline transition, we have used via holes to make a short circuit at the microstrip line and embedded spiral configuration stubs to reduce the electrical length of an open circuit at the slotline end point. For validating the microstrip-slotline technique, we have simulated and implemented the power divider with embedded spiral and via hole configuration circuits at a frequency of 2 GHz. Good agreement between the simulation and the measurement results is obtained at the operating frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.2
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• pp.168-179
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• 2013

The critical point analysis(CA) and impedance matching analysis(IA) are performed and compared for a 4-coil magnetic resonance wireless power transfer system. Because the operating frequency splits at short distance while the efficiency drops drastically at long distance in this system, the optimization technique is needed for either a specific distance or efficiency at the fixed frequency. CA uses the critical point where shows maximum efficiency in the entire range and IA uses the impedance matching technique to achieve maximum efficiency at the specific distance. Comparison result shows that IA is more efficient than CA. Also, it shows one side matching has a tradeoff relationship comparing to both side matching. By using four spiral resonant coils, the analysis was experimentally verified. The measured data agreed well with the calculated data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.114-124
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• 2011

In this paper, we present a 2 GHz compact analog phase shifter with linear phase-tune characteristic. The compact phase shifter was designed base on a lumped all pass network and implemented using a ceramic substrate fabricated with thin-film technique. For a linear phase-tune characteristic, a capacitance of the varactor diode for a tuning voltage was linearized by connecting series capacitor and subsequently produced an almost linear capacitance change. The inductor and bias circuit in the all pass network was implemented using a spiral inductors for small size, which results in the size reduction to $4\;mm{\times}4\;mm$. In order to measure the phase shifter using the probe station, two CPW pads are included at the input and output. The fabricated phase shifter showed an insertion loss of about 4.2~4.7 dB at 2 GHz band and a total $79^{\circ}$ phase change for DC control voltage from 0 to 5 V, and showed linear phase-tune characteristic as expected in the design.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.79-86
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• 2008

This paper presents to improve of isolation characteristics between personal communication service(PCS) antenna In mobile terminal and 2-channel multi input multi output(MIMO) antenna in the wireless broadband Internet(WiBro) band. In order to improve the isolation between each channel antenna, the proposed PCS antenna with an air space of 3 mm height is located on the projected ground plane($25{\times}12mm$) which is very small space$(0.19{\lambda})$ between the 2-channel WiBro-MIMO antenna. The proposed PCS antenna structure is a modified planar inverted F antenna (PIFA) of spiral type with shorting strip line(6${\times}$4 mm). The calculated Isolation values between the proposed PIFA with 3-dimensional structure and the MIMO antenna at Wibro band are about -20dB below and agree well with the measurement. Measured return loss, bandwidth, and gain o# the proposed antenna are -20dB at 1.8GHz, 110MHz(1.76${\sim}$1.87 GHz) band at -10dB below, and 0.05dBi, respectively, Moreover, we confirm that the proposed PCS antenna has no influence on performance and characteristics of the conversional 2-channel WiBro-MIMO antenna.

• Journal of Navigation and Port Research
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• v.27 no.4
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• pp.443-447
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• 2003

In this work. using 0.2 GaAs modulation doped FET(MODFET), a high performance DBS downconverter MMIC was developed for direct broadcasting satellite (DBS) application. Without LNA, the downconverter MMIC showed a very low noise of 4.8 dB, which is lower by 3 dB than conventional ones. A low LO power of -10 dBm was required for the normal DBS operation of the downconverter MMIC. which reduced the power consumption via a removal of LO amplifier on MMIC. It required only a low power consumption of 175 mW, which is lower than 70 percent of conventional ones. The LO leakage power at IF output was suppressed to a lower level than 30 dBm, which removes a bulky LO rejection filter on a board. The fabricated chip, which include a mixer, If amplifiers. LO rejection filter, and active balun, exhibited a small size of $0.84{\times}0.9\textrm{mm}^2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.828-833
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• 2018

It is well known that reflected waves and resonance affect phase distortion. In addition, phase delay can be distorted by antenna impedance. In this study, we analyze the phase delay variation caused by the antenna impedance, considering mutual coupling effects. In addition, we confirm the beam steering characteristics. When was -10 dB and -7 dB, the maximum phase delay error was $18.5^{\circ}$ and $26.5^{\circ}$, respectively. The Monte Carlo simulation with an eight-element linear array antenna demonstrated that the RMS error of the beam steering angle ranged from $0.19^{\circ}$ to $0.4^{\circ}$, and the standard deviation ranged from $0.14^{\circ}$ to $0.33^{\circ}$ when the beam steering angle was in the range of $0^{\circ}$ to $30^{\circ}$, with the uniformly distributed phase error of $18.5^{\circ}$ and $26.5^{\circ}$. The side lobe level increased from 0.74 dB to 1.21 dB by the phase error from the theoretical value of -12.8 dB, with a standard deviation of 0.31 dB to 0.51 dB. This is verified by designing an eight-element spiral array antenna.