• Journal of Korea Society of Industrial Information Systems
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• v.18 no.5
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• pp.15-18
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• 2013

This paper presents an analog front-end for electroencephalogram(EEG) signal processing. Since EEG signals are typically weak and located at very low frequencies, it is imperative to implement an amplifier with high gain, high common-mode rejection ratio(CMRR) and good noise immunity at very low frequencies. The analog front-end of this paper consists of a programmable-gain instrumentation amplifier and a band-pass filter. A frequency chopping technique is employed to remove the low-frequency noise. The circuits were fabricated in 0.18um CMOS technology and measurements showed that the analog front-end has the maximum gain of 60dB and >100dB CMRR over the programmable gain range.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.135-139
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• 2008

In this paper, tunable SC(switched capacitor) 2nd order bandpass $\Sigma-\Delta$(Sigma-Delta) modulator with novel architecture that can adjust the IF band center frequency by one coefficient value is proposed for data conversion in the IF(Intermediate Frequency) band. Its architecture can optionally adjust all the 2nd order noise transfer function in comparison with the conventional architecture. In order to adjust the center frequency, the conventional architecture needs the two variable coefficient values, basic clock and eight clocks. On the other hand, the proposed architecture can adjust the center frequency by one variable coefficient value and basic clock only.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1399-1400
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• 2008

본 논문에서는 TSMC 0.18um 공정을 이용하여 2.45GHz 대역에서 동작하는 RFID 리더에 적용 할 수 있는 전압제어 발진기를 설계하였다. 위상 잡음 특성 향상을 위해 PMOS, NMOS 소자를 대칭으로 구성한 complementary cross-coupled LC 발진기 구조로 설계 하였고 MOS 배렉터를 이용하여 주파수를 가변 하였다. 또한 공정에서 사용되는 인덕터에 차폐 도체면(PGS:Patterned Ground Shield) 구조를 삽입했을 때 인덕터의 품질계수가 약 5.82% 향상되었고. 이에 따른 위상 잡음은 1MHz offset 주파수에서 PGS를 삽입하지 않는 구조에서는 -102.666dBc/Hz 이며, PGS 구조를 삽입한 구조는 -104.328dBc/Hz로 약1.662dBc 정도의 성능이 향상 되었다. 전압제어 발진기 Core 사이즈는 900um ${\times}$ 590um이고 주파수 가변 범위는 배렉터 전압 1.2${\sim}$2.1V에서 249MHz로 11.4% 특성을 보였다. 1.8V공급전압에서 5.76mW의 전력소모를 보였다.

• Information and Communications Magazine
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• v.30 no.7
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• pp.12-17
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• 2013

본 논문에서는 2012년 12월에 표준화가 확정된 NG-PON2(Next Generation-Passive Optical Network2)를 기반으로 하는 액세스 전달망 시스템에서 동작파장을 초기화하는 다양한 방법 및 전송 채널 관리기술에 대한 국내외 동향을 제시하고, 새로운 파장 초기화 및 채널관리 기법을 제안하고 실험결과를 제시한다. 제안되는 기법은 필터링된 파장가변 광원에서 각각 수신된 전기적 신호들간 크기차이를 계산하여 이를 통해, 파장대역을 할당한다. 확보된 파장영역에서 시스템 링크가 물리적으로 연결이 되면, 연결된 광루트를 통해 발생하는 광원의 역반사 효과를 이용하여 전송채널의 동작 파장의 정확도를 향상시킨다. 결정된 채널내에서 광원의 동작 파장의 정확도를 향상시키기 위해서 에코잉(echoing) 기법, 즉, 가입자 송신단에서 전송된 광원이 중앙 기지국 수신단에서 적절하게 수신이 되는 지를 체크하게 된다. 이러한 기법을 이용하여, 광 회선 단말 장치가 광 종단 장치의 광원의 파장을 인지하지 못한 상태에서 동작파장을 찾는 시간이 최대 2초 이내에서 이루어짐을 확인하였다. 또한, 파장 가변형 레이저의 파장특성에 무관하게 동작함을 3개의 파장(1577.86nm, 1578.69nm, 1579.52nm)을 무작위로 선택하여 구동한 결과, 파장 대역 및 동작파장을 소수점 둘째자리까지 확보하는 것을 검증하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.714-720
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• 2009

In this paper, design and the implementation method of a band-tunable ultra-wideband planar doubler are described Microstrip-to-CPS(balun) transition and Microstrip-to-CPW transition are respectively used for input/output matching circuits for the doubler. The Input balun structure allows to apply diode bias, and the doubler output frequency is tunable by changing the diode bias voltage. With the bias voltage of -0.6 V, the measured operating frequency band of the implemented doubler is $10{\sim}20$ GHz, with the bias voltage of $-0.2{\sim}-0.4$ V, the operating frequency band is $10{\sim}30$ GHz, and with 0 V bias, the operating frequency band is $20{\sim}30$ GHz. The doubler provides conversion loss of less than 15 dB and fundamental frequency suppression of 30 dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.10
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• pp.59-64
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• 2008

In this paper an adjustable linear gain equalizer which is operated from 6GHz to 18GHz in order to apply wideband RF circuit System is proposed and fabricated on $Al_2O_3$ substrate using thin film process. An adjustable linear gain equalizer is proposed to T type circuit and designed to aim on variable slope $-7dB{\sim}-13dB$ using the PIN Diode

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.4 s.95
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• pp.345-350
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• 2005

An X-band push-push VCO for low cost applications is proposed. The designed push-push oscillator achieves a wide tuning range in the X-band by the collector bias tuning instead of extra varactor diodes. The measurement shows a wide tuning bandwidth of $900\;\cal{MHz}\;from\;10.9\;\cal{GHz}\;to\;11.8\;\cal{GHz}$ with a drain bias voltage varying from 4 to 9 V, excellent fudamental suppression of $-30\;\cal{dBc}$ and good phase noise of $-115\;\cal{dBc/Hz}\;@\;1\;\cal{MHz}$ offset.

• Journal of IKEEE
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• v.28 no.1
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• pp.72-77
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• 2024

In this paper, a triple-mode frequency-tunable filter is proposed to meet the recent demands of various frequency bands of mobile communication services. This filter has a tunable structure that can adjust the resonance frequency using a variable capacitor. To improve the quality factor, a SIW(Substrate Integrated Waveguide) structure was introduced and a structure that induces three resonance modes was implemented through a circular hole located in the center. The change in electric field distribution and resonance frequency by the variable capacitor was simulated using HFSS, and the change in electric field distribution and resonance frequency of Triple Mode mode was confirmed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.2
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• pp.245-251
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• 2017

The proposed variable pawer divider in this paper is composed of one equal power 2-way Wilkinson power divider, two variable phase shifters with 90-degree phase variation to be connected two output paths of the 2-way power divider, and one branchline coupler to combine output signals of two variable phase shifter. The proposed variable power divider can theoretically have an arbitrary power division ratio ranging from ${\infty}:1$ to ${\infty}:1$ due to 90-degrees phase variation of two phase shifter. The proposed power divider circuit fabricates on laminated TLX-9(h=20 mil, er=2.5; Taconic) with a center frequency of 1.7 GHz. The power division ratio of the fabricated prototype varies from about 1:100 to 200:1, with an input reflection characteristic(S11) of below -16 dB, an insertion loss of about -1.0 dB, and an isolation characteristic of below -17 dB between two output ports in the range 1.65-1.75 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2066-2070
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• 2009

A voltage controlled attenuator using a PIN diode and two resistors of the $\pi$-type fixed attenuator is described in this paper. The proposed variable attenuator operating for a fixed attenuation range has a good input VSWR and a low intermodulation signal. For the low phase shift, a PIN diode is connected with open stub for the purpose of phase compensation. The stub for phase compensation is calculated by the Deloach method and the related circuit theory. This attenuator is easily fabricated on the microstrip and can be normally used in fine control circuits within small attenuation range. The fabricated attenuator for 2110~2170 MHz frequency band has about 4 dB of an attenuation range, $2^{\circ}$ of phase variance, and -20 dB of S11 according to the input voltage from 0 to 2.7 V.