• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.6
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• pp.876-885
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• 2000

A new and simple method is presented for determining the parasitic resistances of MESFET and HEMT from the measured S-parameters under normal active bias without depending on additional DC measurements or iteration or optimization process. The presented method is based on the fact that the difference between source resistance(Rs) and drain resistance(Rd) can be obtained from the measured Z-parameters under zero bias condition. It is possible to define the new internal device including intrinsic device and 3 parasitic resistances by elimination the parasitic inductances and capacitances from the measured S-parameters. Three parasitic resistances are calculated easily from the fact that the real parts of Yint,11 and Yint,12 of intrinsic Y-parameters are zero theoretically and the relations between S-,Z-, Y-matrices. The calculated parasitic resistances using the presented method and successively calculated equivalent circuit parameters give modeled S-parameters which are in good agreement with the measured S-parameters up to 400Hz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1410-1415
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• 2008

This paper proposes an small electronically steerable parasitic array radiator composed of a uniplanar dipole as a feeding element and two dipoles as parasitic elements. The fabricated antenna shows by measurement the $3.3{\sim}4.3\;dB$ gain between $-100{\sim}1000$ azimuth range in the dipole vertical plane and -10 dB return loss within $5.4{\sim}5.9\;GHz$, which includes $5.725{\sim}5.825\;GHz$ UNII band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1620-1627
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• 2001

In this paper, a broadband microstrip antenna for PCS and IMT-2000 service is designed. To obtain the broadband characteristics of an antenna, we utilized the multi-layered structure composed of two foam material layers, parasitic element and aperture coupled feeding network. The broadband characteristic is obtained by changing the size of parasitic element and the height of foam materials. In addition to that, the usage of metal layer at the distance of λ/4 from feed-line, back radiation is reduced. The bandwidth of a single element for VSWR less than 1.3 is about 550MHz. The bandwidth of a designed 1$\times$4 array antenna for VSWR less than 1.3 is about 460MHz. The gain of a designed array antenna is about 11.15∼12.15dBi and the front-to-back ratio is about 30dB.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.8
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• pp.710-717
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• 2015

In this paper, we design an array antenna structure based on a patch ESPAR(Electronically Steerable Parasitic Array Radiator) antenna with three elements for reliable communication in high-speed railway wireless communication. The ESPAR antenna consists of the active element with a single RF-chain and the parasitic elements surrounding an active element. The ESPAR antenna is capable of beamforming by adjusting the reactance of the parasitic element. We propose a vertical array antenna structure based on the patch ESPAR antenna and simulate it according to the change of the number of antennas and the distance between antenna rows. The simulation results show that we can get the maximum beam gain and highest directivity when the distance between antenna rows is ${\lambda}$.

• Journal of IKEEE
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• v.22 no.2
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• pp.413-419
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• 2018

An UWB(Ultra Wide Band) antenna with band rejection characteristics is designed and implemented. A planar radiation patch with slot, parasitic elements on both sides of strip and ground plane on back side consist the proposed antenna. The slot in the radiation patch and parasitic elements contribute corresponding bands rejection characteristics. The slot contributes for WiMAX(World interoperability for Microwave Access, 3.30~3.70 GHz) band rejection and parasitic elements contribute for X-Band(7.25~8.395 GHz) rejection. Ansoft's HFSS(High Frequency Structure Simulator) was used to design the proposed antenna and performance simulations. Simulation result showed VSWR(Voltage Standing Wave Ratio) less than 2.0 for UWB band except for dual rejection bands of 3.30~3.86 GHz and 7.21~8.39 GHz. And VSWR measurement result for the implemented antenna shows less than 2.0 for 3.10~10.60 GHz band except dual rejection bands of 3.25~3.71 GHz and 7.25~8.46 GHz.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.12
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• pp.10-16
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• 2003

To analyze the effects of the air-bridge parasitic capacitances on the performance of coplanar waveguide pseudomorphic high electron mobility transistors (CPW PHEMTs), the gate-to-air-bridge ( $C_{ag}$ ) and the drain-to air-bridge ( $C_{ad}$ ) capacitances were taken into account plus the conventional pinched-off cold. FET circuit model. To examine the effects of the parasitic capacitances due to the air-bridges, a variety routing schemes for the air-bridge interconnection were adopted for fabricating the 0.1-${\mu}{\textrm}{m}$ $\Gamma$-gate length CPW HEMT's. According to air-bridge schemes, the $S_{21}$ gain is affected considerably. From the results of the fabricated CPW PHEMT, the $C_{ag}$ and $C_{ad}$ is one of the important factor of decreasing the gain of HEMTs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.6
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• pp.689-697
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• 2016

In this paper, we design and implement SPA (Switched Parasitic Antenna) antenna which can control its beampattern using multiple parasitic elements. By applying SPA antenna to wireless communication system and implementing beamforming scheme, we show that SPA antenna can be used to improve the performance of wireless communication systems. SPA antenna consists of a single active antenna and multiple parasitic elements around the active one, and can control its beampattern by switching the parasitic elements. Using this characteristic of the SPA antenna, it is possible to impelemtent beamforming technique with single RF chain, which enables to design low cost, low complexity and low power wireless communication systems. In order to verify the beamforming gain, we measure and analyze the system level performance, such as SNR, PER, and throughput.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.145-146
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• 2016

일반적인 boost PFC 컨버터는 한 개의 스위칭 소자를 사용하고 구조가 간단하지만 높은 도통손실과 스위칭 손실 때문에 낮은 효율을 갖는다. bridgeless boost PFC 컨버터는 일반적인 boost PFC 에 비해 낮은 손실을 갖는 이점이 있다. 또한 컨버터의 동작 모드 중 CRM 방식은 낮은 스위칭 손실을 갖는 이 점이 있다. 본 논문에서는 이러한 CRM 모드로 동작하는 bridgeless boost PFC 컨버터를 해석하는 경우 기존의 방법으로 해석하여 구현하면 주파수가 커지는 영역에서 오차가 커지게 된다. 따라서 본 논문에서는 반도체 스위치의 기생 커패시터를 추가하여 해석하는 것을 제안하였다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.5
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• pp.197-203
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• 2016

In this paper, the dipole antenna that can control a beam steering were designed for attaching on LEO(Low Earth Orbit) small satellite. The proposed antenna was based on Yagi-Uda antenna. The parasitic element was proposed as a T-shape. Depending on the state of open or short at the end of a vertical element, we can choose a characteristic of the parasitic element with fixing a vertical element length of the parasitic element. Using this characteristic, we designed the director element and reflector element. The proposed antenna was designed to receive UHF 436.5 MHz. Antenna gain was chosen by link budget between one satellite and the other satellite or between the satellite and the ground station. By changing a vertical element length which is the largest variable that chooses an antenna characteristic, we confirmed that ${\lambda}/2$ length transformer has a result that improve 0.5 dB in comparison ${\lambda}/4$ length transformer from maximum gain direction. In production, we made an on/off switch composed of a diode, capacitor, and inductor control an open and short at the end of the parasitic element. As a result, the gain of antenna used in a link between one satellite and the other satellite had average 5.92 dBi. And the gain of antenna used in a link between the satellite and the ground station had average 0.99 dBi.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.2
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• pp.1-10
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• 1999

Direct extraction of FET's small signal model parameters needs predetermined parasitic elements usually obtained under forward cold FET conditionl This paper derives analytic intrinsic model for cold FET's and shows that normal cold FET condition can replace forward cold FET condition for extracting parasitic elements. Then, we track the error of hot FET's small signal model bounded by the cold FET condition and examine the validness of cold parasitic resistances by checking the existence of the error minimum.