• JSTS:Journal of Semiconductor Technology and Science
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• 제9권3호
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• pp.153-159
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• 2009

A CMOS frequency synthesizer for $5{\sim}6$ GHz UNII-band sub-harmonic direct-conversion receiver has been developed. For quadrature down-conversion with sub-harmonic mixing, octa-phase local oscillator (LO) signals are generated by an integer-N type phase-locked loop (PLL) frequency synthesizer. The complex timing issue of feedback divider of the PLL with large division ratio is solved by using multimodulus prescaler. Phase noise of the local oscillator signal is improved by employing the ring-type LC-tank oscillator and switching its tail current source. Implemented in a $0.18{\mu}m$ CMOS technology, the phase noise of the LO signal is lower than -80 dBc/Hz and -113 dBc/Hz at 100 kHz and 1MHz offset, respect-tively. The measured reference spur is lower than -70 dBc and the power consumption is 40 m W from a 1.8 V supply voltage.

• Current Optics and Photonics
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• 제2권5호
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• pp.395-399
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• 2018

This article investigates the mechanism of electronic signal phase noise degradation induced by laser phase noise in optical links comprising optical resonators. Through theoretical derivation, we find that the phase noise of the output electronic signal has the same spectral shape of optical intensity noise as the output of the optical resonator. We propose that the optical resonator transfers laser phase noise to light intensity fluctuation and then the intensity fluctuation is converted to electric phase noise through AM-PM conversion mechanism in the photodiode. An optical link comprising a Fabry-Perot resonator was constructed to verify the proposed mechanism. The experimental results agree with our theoretical prediction verifying that the supposition is correct.

• ETRI Journal
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• 제46권2호
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• pp.238-249
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• 2024

Equivalent-time sampling can improve measurement or sensing systems because it enables a broader frequency band and higher delay resolution for periodic signals with lower sampling rates than a Nyquist receiver. Meanwhile, a digital down-conversion (DDC) technique can be implemented using a straightforward radio frequency (RF) circuit. It avoids timing skew and in-phase/quadrature gain imbalance instead of requiring a high-speed analog-to-digital converter to sample an intermediate frequency (IF) signal. Therefore, when equivalent-time sampling and DDC techniques are combined, a significant synergy can be achieved. This study provides a parameter design methodology for optimal equivalent-time sampling using DDC.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.182-185
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• 2014

본 논문에서는 지연시간 최소화를 위한 고속 데이터 광 전송용 ADC 개발에 관한 연구를 진행하였다. 기존 광 중계기의 전송 방식은 데이터 신호 변환에서 $6{\mu}s$이상의 지연시간을 갖고 있어 고속 데이터 전송 및 신호 변환에 제한을 받고 있으므로 이를 직접 변환 방식을 이용하여 데이터 신호 변환 시 지연시간을 $2{\mu}s$ 이내로 줄이는 새로운 기술의 개발이 요구된다. 이동통신 LTE, LTE advanced 등의 서비스 전송망 구축에 필요한 신호변환 부품 핵심기술의 발전이 요구되고 있으므로, 본 논문에서는 신호변환 단계에서 지연시간을 획기적으로 줄일 수 있는 기술을 적용하여 $3{\mu}s$의 지연시간을 갖는 ADC를 개발하였다.

• 정보저장시스템학회논문집
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• 제1권1호
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• pp.23-28
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• 2005

This paper investigates the effects of disk thickness and Pemto slider on PES(position error signal) for high TPI(track per inch) drives above 150kTPI at early stage of their development. In order to reduce the disk flutter which becomes a dominant contributor to the TMR, the thicker disks with both 63 and 69mi1 have been used. Also, PES of a Pemto slider with thinner thickness than Pico slider has been estimated to decrease the conversion factor of disk motion in axial direction to head off-track motion. A frequency-domain PES estimation and prediction tool has been developed via measurement of disk flutter and HSA(head stack assembly) forced vibration. It has been validated by the measured PES in drive level. Based on the model and measurement of disk flutter, PES of a drive with the thicker disk and Pemto slider is predicted and their impact is investigated.

• 산업기술연구
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• 제23권A호
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• pp.55-61
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• 2003

In this study, a signal processing and related techniques for development of a weight measuring system using a digital loadcell which is able to satisfy the important properties of WIM (weighing-in-motion) system have been investigated. A fast and high accurate signal processing of the digital load cell sensor for weighing-in-motion system is presented. A/D conversion system is constructed to realize a stable A/D conversion and signal processing algorithm using DSP and microprocessor. A new technique for vibration and measuring speed of the system is also investigated. The proposed method was applied to the actual design and the experimental results showed good performance of the weighing speed and stability.

• 전자공학회논문지S
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• 제35S권4호
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• pp.118-127
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• 1998

In this paper, we propose a voice personality transformation method which makes one person's voice sound like another person's voice. In order to transform the voice personality, vocal tract transfer function is used as a transformation parameter. Comparing with previous methods, the proposed method can obtain high-quality transformed speech with low computational complexity. Conversion between the vocal tract transfer functions is implemented by a linear mapping based on soft clustering. In this process, mean LPC cepstrum coefficients and mean removed LPC cepstrum modeled by the low dimensional vector are used as transformation parameters. To evaluate the performance of the proposed method, mapping rules are generated from 61 Korean words uttered by two male and one female speakers. These rules are then applied to 9 sentences uttered by the same persons, and objective evaluation and subjective listening tests for the transformed speech are performed.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.197-206
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• 2003

It is intended to retrieve the time history of displacement from measured acceleration signal. In this study, the word retrieving means reconstructing the time history of original displacement signal from already measured acceleration signal not just extracting various information using relevant signal processing techniques. Unlike extracting required information from the signal, there are not many options to apply to retrieve the time history of displacement signal, once the acceleration signal is measured and recorded with given sampling rate. There are two methods, in general, to convert measured acceleration signal into displacement signal. One is directly integrating the acceleration signal in time domain. The other is dividing the Fourier transformed acceleration signal by the scale factor of - $\omega$$^2$and taking the inverse Fourier transform of it. It turned out both the methods produced a significant amount of errors depending on the sampling resolution in time and frequency domain when digitizing the acceleration signals. A simple and effective way to convert the time history of acceleration signal into the time history of displacement signal without significant errors is studied here with the analysis on the errors involved in the conversion process.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.179.1-179
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• 2001

Successive image contrast enhancement was used to direct digital radiography system. This system was accurately required acquisition signal in each pixel. But, applied high electric field in a-Se thin film for x-ray conversion layer was caused to acquisition signal distortion, then bring low image contrast. The purpose of this study was to reduce the signal distortion, carried out different electrode size.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2002년도 정기총회 및 학술대회
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• pp.9-14
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• 2002

Direct-conversion receiver(DCR) architecture has superior advantages in size, cost, and power over superheterodyne receiver architectures. However, the use of direct-conversion receiver architecture has been limited due to the direct-current offset noise. The ac coupling, which is used to overcome the direct-current offset noise, causes an inter-symbol interference(ISI), whose effects can be effectively mitigated using an equalizer. In this paper, the performance of a direct-conversion receiver with ac coupling in the presence of direct-current offset is analyzed via computer simulation. The simulation result shows that by using decision feedback equalizer with LMS(Least Mean Square) algorithm, signal-to-noise ratio loss of the direct-conversion receiver compared to the idea receiver can be reduced to less than 1㏈ for corner frequencies as large as 10% of the symbol rate.