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A Novel Design of High Power Amplifier Employing Photonic Band Gap in Millimeter Wave Band
Chulhun Seo 한국전자파학회JEES 2006 Journal of Electromagnetic Engineering and Science Vol.6 No.2
In this paper, we have designed and fabricated the high power amplifier employing PBG(Photonic Band-Gap Structure) to improve the linearity of the amplifier in the millimeter wave band. The fabricated amplifier using MMIC(TGA1073G) has operated about 24 ㎓ band and the PBG has resulted in 35 ㏈ suppression about 49 ㎓ where the second harmonic occurs due to the amplifier. As a result, the output power has been 24.43 ㏈m and 13.2 ㏈c of the IMD has been improved. Also, the PAE is obtained to 14.96 % of the amplifier employing the PBG structure in Ka band.
Omnidirectional Resonator in X-Y Plane Using a Crisscross Structure for Wireless Power Transfer
Chulhun Seo,Donggeon Kim 한국전자파학회JEES 2015 Journal of Electromagnetic Engineering and Science Vol.15 No.3
Magnetic resonant coupling is more efficient than inductive coupling for transferring power wirelessly over a distance. However, a conventional resonant wireless power transfer (WPT) system requires a transmitter and receiver pair in exactly coaxial positions. We propose a resonator that can serve as an omnidirectional WPT system. A magnetic field will be generated by the current flowed through the transmitter. This magnetic field radiates omnidirectionally in the x-y plane because of the crisscross structure characteristic of the transmitter. The proposed resonator is demonstrated by using a single port. To check the received S21 and transfer efficiency, we moved the receiver around the transmitter at different distances (50?350 mm). As a result, the transmission efficiency is found to be 48?54% at 200 mm.
Chulhun Seo 한국전자파학회JEES 2005 Journal of Electromagnetic Engineering and Science Vol.5 No.4
In this paper, we introduced a band-pass filter employed the PBG structure and the aperture on the ground together. The harmonics of band pass filter have been suppressed by employing the PBG structure and the bandwidth of it has been broadened by using the aperture on the ground. The designed PBG cells have three different sizes. The largest cells, the middle cells, and the smallest cells have suppressed the multiple of second harmonics, the multiple of third harmonics, and the multiple of fifth harmonics, respectively. The center frequency has been 2.18 GHz. The bandwidth has been increased from 230 ㎒ up to 310 ㎒(80 ㎒, about 35 %) by the aperture and the ripple characteristics in passband have been improved and the harmonic frequencies have been suppressed about 30 ㏈ by the PBG.
Chulhun Seo 한국전자파학회JEES 2005 Journal of Electromagnetic Engineering and Science Vol.5 No.4
In this paper, PBG structure and feedforward circuit has been used to suppress the phase noise of the oscillator. Microstrip line resonator have low Q, but we can obtain high LO power by feedforward circuit and improve the resonator Q by the PBG, simultaneously. The proposed oscillator which uses PBG and feedforward circuit shows 0~20 ㏈ phase noise reduction compared to the conventional oscillator. We have obtained -115.8 ㏈c of phase noise at 100 ㎑ offset from 2.4 ㎓ center.
서철헌 崇實大學校 生産技術硏究所 1997 論文集 Vol.27 No.1
In order to construct a highly selective bandpass optical receiver, a high-Q resonance at a single, particular frequency must be established to filter the optical spectrum. An "ideal" receiver would spacially separate the on-resonant field component from the off-resonant components without reflection or absorption, and without significant distortion of the pulse envelope when using digitally encoded transmission. The single side coupler presented in this paper use quarter-wave shifted distributed feedback (QWS-DFB) gratings to generate the optical resonances, and waveguide couplers to steer the on-resonant signal from the main waveguide to a secondary wavegude. The theory of the waveguide coupler and grating reflctors has been mentioned in this paper. This paper introduces the resonant transmitter, the resonant reflector, the single side-coupled receiver.
PBG 구조를 이용한 Ka Band 전력증폭기 성능개선에 관한 연구
서철헌,Seo Chulhun 대한전자공학회 2004 電子工學會論文誌-TC (Telecommunications) Vol.41 No.1
본 논문에서는 밀리미터파 대역 전력증폭기가 출력단에 PBG (photonic bandgap structure) 구조를 설치함으로써 성능개선 되었다 PBG 구조는 Ka 대역에서 저역통과 특성을 갖도록 최적화되었다. 전력증폭기의 하모닉은 PBG 구조에 의하여 억제되었고 50 GHz에서 40dBc 개선되었다 전력증폭기의 IMD와 PAE는 PBG에 의하여 기존의 전력증폭기에 비하여 각각 $15\%$와 $25\%$ 개선되었다. The performances of millimeter wave Power amplifier have been improved by using PBG (photonic bandgap structure) in this paper. The PBG structure has been optimized to obtain the lowpass characteristics in Ka band and employed at output port of Ka band power amplifier. The harmonics of the power amplifier have been suppressed by the PBG of output port and the proposed PBG has suppressed the second harmonic to 40dBc around 50 GHz. The improvements of IMD and PAE of the amplifier employing the PBG structure are obtained $15\%$ and $25\%$, compared with those of the conventional Ka band power amplifier, respectively.
PBG 구조를 이용한 대역통과 여파기 고조파 억제에 관한 연구
서철헌,Seo Chulhun 대한전자공학회 2004 電子工學會論文誌-TC (Telecommunications) Vol.41 No.1
A bandpass filter has been designed by employing the PBG structure and the aperture on the ground together in this paper. The harmonics of band pass filter have been suppressed by employing the PBG structure and the bandwidth of it has been broadened by using the aperture on the ground. The three kinds of PBG structures has been combined to suppress the harmonics of the filter The center frequency of filter is 2.2 GHz and the bandwidth has been increased from $40\%$ by the aperture and all harmonics were suppressed about 35dBc by the PBG. The insertion loss has been reduced 3.0dB to 2.6dB. 접지면에 PBG와 Aperture를 설치함으로써 고성능 대역통과 여파기를 설계하였다. 대역통과 여파기의 하모닉 특성은 PBG 구조에 의하여 개선되었고 대역폭은 Aperture에 의하여 확대되었다. 세가지 크기를 갖는 PBG 구조가 결합되어 새로운 PBG 구조가 도출되었다. 설계 중심 주파수는 2.2 GHz이었고 대역폭은 Aperture에 의하여 $40\%$ 확대되었다.
Cho, Sunghee,Seo, Chulhun Wiley Subscription Services, Inc., A Wiley Company 2007 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS - Vol.49 No.2
<P>In this article, adaptive bias circuit and PBG structure have been employed to achieve high power added efficiency (PAE) and high third-order intermodulation (IM3) suppression in power amplifier simultaneously. The dc bias voltage of the gate in FET has been controlled by envelope of the input signal. The PBG structure has been employed to suppress IM3 on the output port of the power amplifier. The PBG structure was optimized to suppress the second harmonics of the amplifier. IM3 and PAE of the proposed power amplifier using adaptive bias circuit and PBG structure has been improved by 2.73 dBc, and by 35.54%, respectively. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 443–446, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22158</P>
A 28-GHz Wideband 2×2 U-Slot Patch Array Antenna
Nanae Yoon,Chulhun Seo 한국전자파학회JEES 2017 Journal of Electromagnetic Engineering and Science Vol.17 No.3
In this study, a 28-GHz U-slot array antenna for a wideband communication system is proposed. The U-slot patch antenna structure consists of a patch, two U-shaped slot, and a ground plane. With the additional U-slot, the proposed antenna has around 10% of bandwidth at –10 dB. To increase gain, the U-slot antenna is arrayed to 2×2. The proposed antenna is designed and fabricated. The 2×2 array antenna volume is 41.3 mm × 46 mm × 0.508 mm. The proposed antenna was measured and compared with the simulation results to prove the reliability of the design. The bandwidth and gain of the measurement results are 3.35 GHz and 13 dBi, respectively and the operating frequency is around 28 GHz.