• Journal of electromagnetic engineering and science
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• 제18권4호
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• pp.215-220
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• 2018

This study presents a dual-band polarization-reconfigurable antenna that comprises a large square patch with a pair of corner-cut edges and two small square patches with a shorting via. Two PIN diodes are located between the large square patch and two small square patches. Depending on the bias state applied to the two PIN diodes, each small patch may be disconnected or connected to the large square patch. As a result, the proposed antenna can provide polarization reconfigurability between two orthogonal linear polarizations. Further, the proposed antenna operates at 2.51 GHz and 2.71 GHz. From the measured results, the proposed antenna shows a 10 dB bandwidth of 2.39% (2.49-2.55 GHz) and 2.58% (2.68-2.75 GHz). In this work, the frequency ratio can be easily controlled by changing the size of the small patch.

• 한국전자파학회지:전자파기술
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• 제6권2호
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• pp.3-10
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• 1995

p-i-n 다이오드를 이용한 위상변위기를 설계하고, 그 특성을 해석하였다. 큰 위상변화는 가변선로형 위상변위기와 하이브리드 브랜치라인위상변위기로 실현하고, 작은 위상변화는 부하선로형 위상변위기로 실현하였다. 컴퓨터 시뮬레이션을 통하여 중심주파수 3.2GHz에서 좋은 위상변화특성이 유지됨을 확인하였고, 실제 제작된 위상변위기 특성도 이론치에 매우 근사하게 나타났다.

• 한국전자파학회논문지
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• 제7권2호
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• pp.178-185
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• 1996

In this paper, a theoretical analysis of a wide band distributed mixer using a dual-gate GaAs MESFET's(DGFET) is introduced. Based on low noise mixer mode(LNM) region modeling of DGFET, variation of g/sub m/ and conversion gain are presented versus bias. The distributed mixer is composed of drain and gate transmission line, m-derived image impedance matching circuits at each input and output port, and DGFET's. Through computer simulation, wide-band characteristics of designed distributed mixer are confirmed. And, it is certificated that LO/RF isolation between gate 1 and gate 2 is obtained more than 15dB.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2001년도 종합학술발표회 논문집 Vol.11 No.1
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• pp.218-221
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• 2001

In this paper, High Q Inductor using negative resistance circuit and the ceramic inductor was designed and fabricated at 2GHz. It was Improved the inductor of Q=90 using a inductor with Q=30 added to negative resistance circuit at 2GHz. As a result, at the bias condition of 3V and 16mA, the output power and phase noise in the operation frequency 2.01GHz are 5dBm and -115.34dBc/Hz at 100kHz offset from carrier, respectively. Phase noise was improved -10dBc/Hz at 100kHz offset compared to only using ceremic inductor.

• 한국전자파학회논문지
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• 제9권6호
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• pp.843-849
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• 1998

24GHz 대역의 WLL 시스템용 전압제어발진기(Yca)를 설계하고 제작하였다. 위상잡음(C/N) 특성을 개선하기 위하여 품질계수가 높은 유전체 공진기를 공진부의 인덕터로 사용하였다. 5 V, 10 mA 바이어스 조건 에서 VCO를 측정한 결과 2210-2240 MHz의 주파수 대역에서 출력은 0 dBm, 위상잡음 특성은 10 kHz offset에서 100 dBc/Hz으로 매우 우수한 특성을 나타내었다. 따라서 제작된 VCO는 WLL 시스템에 적용할 수 있다고 생각된다.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.100-103
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• 2003

A Ku-band Push-push VCO for low cost applications is proposed. The proposed push-push oscillator achieves a wide tuning range in Ku-band by the collector bias tuning instead of extra varactor diodes. The measurement shows a wide tuning range of 900MHz, fundamental suppression of -30dBc and good phase noise of -115dBc@1MHz offset.

• 한국전자파학회논문지
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• 제11권6호
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• pp.893-899
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• 2000

본 논문에서는 0.65 $\mu$m CMOS 공정을 이용한 900MHz 대역의 저잡음 증폭기를 설계하였다. 입력 매칭은 전력소모가 가정 적고 NF도 가장 작은 인덕터 종단 정합회로를 사용하였다. 온칩 상에 바이어스 안정화를 포한시켰으며, 전원은 3V를 공급하였을 때 전력 소모는 39mW이다. 설계된 저잡음 증폭기의 특성능 900MHz 대역에서 13.2dB의 이득과 4.8dB의 Noise Figure가 측정이 되었다. 입력 반사손실으 -26dB, 츨력반사 손실은 -17dB을 얻었으며, 입력 1-dB 억압 -12dBm을 얻었다.

• 한국전자파학회논문지
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• 제9권2호
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• pp.219-225
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• 1998

A voltage controlled oscillator for the local oscillator in 380 MHz TRS handset is designed and fabricated. To improve the phase noise characteristics, the NEC's 2SC4226 transistor with NF=1.2 at 1 GHz and Toshiba's 1SV229 varactor diode with Q=70 are used. And an inductor of VCO is realized by microstrip line. At the bias condition of 5 V and 10 mA, the output power and phase noise in the operating frequency range of 357∼387 MHz are above 3.7 dBm and 111 dBc/Hz at 12.5KHz offset from the carrier, respectively. And FM sensitivity deviation are within ±0.4 KHz. This VCO is well suited for TRS handset.

• Journal of electromagnetic engineering and science
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• 제15권2호
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• pp.63-75
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• 2015

The CMOS power amplifier (PA) is a promising solution for highly-integrated transmitters in a single chip. However, the implementation of PAs using the CMOS process is a major challenge because of the inferior characteristics of CMOS devices. This paper focuses on improvements to the efficiency and linearity of CMOS PAs for modern wireless communication systems incorporating high peak-to-average ratio signals. Additionally, an envelope tracking supply modulator is applied to the CMOS PA for further performance improvement. The first approach is enhancing the efficiency by waveform engineering. In the second approach, linearization using adaptive bias circuit and harmonic control for wideband signals is performed. In the third approach, a CMOS PA with dynamic auxiliary circuits is employed in an optimized envelope tracking (ET) operation. Using the proposed techniques, a fully integrated CMOS ET PA achieves competitive performance, suitable for employment in a real system.

• Journal of electromagnetic engineering and science
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• 제7권2호
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• pp.64-68
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• 2007

An InGaP/GaAs HBT based differential Colpitts voltage control oscillator(VCO) is presented in this paper. In the VCO core, two switching transistors are introduced to steer the core bias current to save power. An LC tank with an inductor quality factor(Q) of 11.4 is used to generate oscillation frequency. It has a superior phase noise characteristics of -130.12 dBc/Hz and -105.3 at 1 MHz and 100 kHz frequency offsets respectively from the carrier frequency(1.566 GHz) when supplied with a control voltage of 0 volt. It dissipates output power of -5.3 dBm. Two pairs of on-chip base collector (BC) diodes are used in the tank circuit to increase the VCO tuning range(168 MHz). This VCO occupies the area of $1.070{\times}0.90mm^2$ including buffer and pads.