• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.12
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• pp.2716-2724
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• 2012

In this paper, a Phase Difference-to-Voltage Converter (PDVC) has been introduced into a conventional fractional-N PLL to suppress fractional spurs. The PDVC controls charge pump current depending on the phase difference of two input signals to phase frequency detector. The charge pump current decreases as the phase difference of two input signals increase. It results in the reduction of fractional spurs in the proposed fractional-N PLL. The proposed fractional-N PLL with PDVC has been designed based on a 1.8V $0.18{\mu}m$ CMOS process and proved by HSPICE simulation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.242-245
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• 2001

본 논문은 디지털 위성용 하향변환기에 적용되는 고안정 전압제어 마이크로파 발진기의 위상잡음 특성을 분석하였다. 전압제어 마이크로파 발진기는 능동소자의 비선형 등가모델과 궤환회로의 영향을 고려하여 유전체 공진 마이크로파 발진기를 위상잡음과 출력 전력에 절충(trade-off)하여 설계하였고, 13.25GHz의 발진주파수에서 출력이득은 12dBm이고, 위상잡음은 옵셋 주파수 100KHz 에서 -107.91dBc를 보였다. 바렉터 다이오드 동작에 의한 튜닝 범위는 2MHz/V로 위상동기 발진기에 응용할 수 있음을 보였다.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.4
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• pp.434-438
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• 2001

Piezoelectric torsional transducers have been fabricated to generate torsional waves in a rod. The principle of generating torsional wane is based on the use of the circumferential shear motion derived by axial voltage exerted on the piezoelectric disk poled in the circumferential direction. The natural frequency or the piezoelctric torsional dish has been reduced by fabricating Langevin-type torsional transducers. The natural frequecies of the fabricated transducers have been measured and have shown good agreement with the characteristics predicted by analysis.

• Journal of Sensor Science and Technology
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• v.11 no.3
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• pp.145-154
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• 2002

NiCr-heaters with three different thicknesses ranging from 400 nm to 800 nm were fabricated and their characteristics were compared for the purpose of developing a chromel-alumel multijunction thermal converter for low input voltage with low frequency. The thermoelectric effect-induced AC-DC voltage transfer difference of the thermal converter with a built-in NiCr-heater of 400 nm-thickness was ${\pm}0.51{\sim}1.69\;ppm$ in the DC reversing frequency of $40\;Hz{\sim}10\;kHz$ with appling $0.5\;V_{rms}$ and the difference was increased to ${\pm}40{\sim}{\pm}115\;ppm$ in the frequency of $40\;Hz{\sim}1\;MHz$, when both thermoelectric effects and frequency effects were considered, showing the thermal converter would be suitable for the low input voltage application with low frequency.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.50-56
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• 2015

An efficient fast response hysteretic buck converter suitable for mobile application is propoesed. The problems of large output ripple and difficulty in using of small power inductor that conventional hysteretic converter has are improved by adding ramp generator. and the changeable switching frequency with load current is fixed by adding a delay time control circuit composed of PLL structure resulting in decrease of EMI noise. The circuits are implemented by using BCDMOS 0.35um 2-polt 4-metal process. Measurement results show that the converter operates with a switching frequency of 1.85MHz when drives 80mA load current. As the converter drives over 170mA load current, the switching frequency is fixed on 2MHz. The converter has output ripple voltage of less 20mV and more than efficiency 85% with 50~500mA laod current condition.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.137-140
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• 2008

본 논문에서는 높은 주파수에서 이미지신호에 따른 하향변환기의 선현성을 우수하게 나타내기 위하여 이미지 제거 특성이 우수한 능동소자를 선택하여 VSAT 위성통신용 Ka-band 하향변환기를 설계 및 제작하였다. 하향변환기의 구성은 저잡음 증폭기단, 이미지 제거 필터, 주파수 혼합기, 주파수 체배기, 전압제어 감쇄단 및 IF단으로 구성하였고, RF 경로의 동작 유무를 판단하기 위하여 국부 루프 경로로 구성되어 있다. 하향변환기의 이득은 $11.73{\sim}13.23dB$, 잡음지수 4.4dB 이하, 50dBc 이상의 이미지 제거 특성을 나타내어, 본 논문에서 제작한 하향변환기는 고속/광 대역폭을 가지는 디지털 통신 시스템에도 적용할 수 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.665-667
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• 2010

In this paper, the method to detect the IM(Inter Modulation) components of power amplifier is proposed by using frequency down-convertor. Output signals of power amplifier which is coupled by 20dB coupler and divided by power divider are applied to RF and LO of the frequency converter. It could be found the magnitude of IM components of power amplifier as a converted DC voltage which is come from the difference between 3th and 5th IM component. The detected DC voltage values are changed from 0.72V to 0.9V when 3rd IM component level changed from -26.4dBm to +2.15dBm and 5th IM component level changed from -34.2dBm to -12.89dBm as the Vgs of 3W power amplifier is changed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.74-84
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• 1998

A doubly resonant ultrasonic transducer has been designed as an attempt to increase the bandwidth of underwater transducers. The dual resonance conditions were accomplished by attaching a single acoustic matching layer on the front face of a Tonpilz transducer consisted of an aluminum head, a piezoelectric ring, a brass tail and a prestress bolt. A modified Mason's model was used for the performance analysis and the design of transducers, and the constructed transducers were tested experimentally and numerically by changing the impedances and thicknesses of the head, tail and matching layers in the water tank. Two distinct resonance peaks in the transmitting voltage response(TVR) of a developed transducer were observed at 34.3 and 40.4 kHz, respectively, with the difference frequency of 6.1kHz and the center frequency of 37.2kHz. The values of TVR at these frequencies were 136.5 dB re $1\;\muPa/V$ at 34.3 kHz and 136.8 dB re $1\;\muPa/V$ at 40.4 kHz, respectively. Reasonable agreement between the experimental results and the numerical results was achieved. From this result, it is expected that the generation of the distinct resonances at any two desired frequencies can be achieved through the proper choice of the matching layer to provide the impedance transformation between the transducer and the medium.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.1
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• pp.85-95
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• 1998

The broadband ultrasonic transducers have been designed to use in obtaining the broadband echo signals from fish schools in relation to the identification of fish species. The broadening of bandwidth was achieved by attaching double acoustic matching layers on the front face of a Tonpilz transducer consisted of an aluminum head, a piezoelectric ring, a brass tail and to evaluate the performance characteristics, such as the transmitting voltage response(TVR) of transducers. The constructed transducers were tested experimentally and numerically by changing the parameters such as impedances and thicknesses of the head, tail and matching layers, in the water tank. Also, the developed transducer was excited by a chirp signal and the received chirp waveforms were analyzed. According to the measured TVR results, the available 3 dB bandwidth of the transducer with double matching layers of an $Al_O_3/epoxy$ composite of 7 mm thick and a polyurethane window of 18 mm thick was 7.3 kHz with a center frequency of 38.8 kHz, and the maximum and the minimum values of the TVR in this frequency region were 135.7 dB and 132.7 dB re $1\;{\mu}Pa/V$ at 1 m, respectively. Also, the available 3 dB bandwidth of the transducer with double matching layers of an $Al_O_3/epoxy$ composite of 11 mm thick and a polyurethane window of 15 mm thick was 6.2 kHz with a center frequency of 38.6 kHz, and the maximum TVR value in the frequency region was 136.3 dB re $1\;{\mu}Pa/V$ at 1 m. Reasonable agreement between the experimental results and the numerical results for the TVR of the developed transducers was achieved. The frequency dependant characteristics of experimentally observed chirp signals closely matched to the measured TVR results. These results suggest that there is potential for increasing the bandwidth by varying other parameters in the transducer design and the material of the acoustic matching layers.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.309-315
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• 1998

This paper describes an 8b 52 MHz CMOS subranging analog-to-digital converter (ADC) for Integrated Services Digital Network (ISDN) applications. The proposed ADC based on the improved time-interleaved architecture removes the holding time which is typically observed in the conventional double-channel subranging ADCs to increase throughput rate. Moreover, the ADC employs the interpolation technique in the back-end subranging ADCs far residue signal processing to minimize die area and power consumption. The fabricated and measured prototype ADC in a 0.8 um n-well double-poly double-metal CMOS process typically shows a 52 MHz sampling rate at a 5 V supply voltage with 230 mW, and a 40 MHz sampling rate at a 3 V power supply with 60 mW power consumption.