• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.694-697
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• 2016

Up-converted phase noise, which is induced by the low-frequency relative intensity noise (RIN) of a laser through AM-PM conversion within a photodetector (PD), is first measured here by means of a cross-correlation method. Our proposed measurement system can isolate the RIN-induced phase noise from noise contributions of other components, such as amplifiers, modulators, and mixers. In particular, shot noise and thermal noise generated from the PD are also suppressed by this method, so that standalone characteristics of the RIN-induced phase noise can be obtained. Experimental results clearly show the quantitative relationship between the RIN-induced phase noise and the incident optical power of the PD. Our findings indicate that the least RIN-induced phase noise appeared at the saturation point of the PD, which is about -162 dBc/Hz at 10 kHz offset.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.236-240
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• 1997

We compare feedback wavelength-dependent performances of all-optical gain-clamped 980-nm pumped erbium-doped fiber amplifiers. In a 2.5-Gbps 8-channel WDM system, we have measured and compared gain compressions, signal power variations due to cross-saturation, power penalties caused by relaxation oscillations and noise figures for three different feedback wavelengths - 1532, 1543, and 1565 nm.

• Journal of Semiconductor Engineering
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• v.1 no.2
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• pp.64-73
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• 2020

As CMOS technology scales down, the design of analog signal processing circuit becomes far more difficult because of steadily decreasing supply voltage and smaller intrinsic gain of transistors. With sub-1V supply voltage, the conventional analog signal processing relying on high-gain amplifiers is not an effective solution and different approach has to be sought. One of the promising approaches is "time-domain analog signal processing" which exploits the improving switching speed of transistors in a scaled CMOS technology. In this paper, various time-domain analog signal processing techniques are explained with some experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.944-949
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• 2009

A simplified power control technique for electronic ballasts of HID lamps is proposed. This power calculator and controller consist of regular operational amplifiers with some passive elements and form simple add operation circuit. From a mathematical model of designed ballast with proposed power controller, the control performance and stability are analyzed by using Matlab and the results show that the stable starting characteristics and steady state characteristics of HID lamp are appropriately guaranteed. The experimental results of the prototype ballast coincide with the simulation results.

• Journal of information and communication convergence engineering
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• v.17 no.4
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• pp.227-233
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• 2019

In long-haul optical communication system consisting of standard single-mode fiber spans and fiber amplifiers, such as the erbium-doped fiber amplifier, performance is deteriorated by signal distortion due to chromatic dispersion and nonlinearity of the fiber. A combination of dispersion management and optical phase conjugation is an effective technique to compensate for the distortion. In an optical link configured by this combination, a dispersion map mainly affects the compensation of the distorted optical signals. This paper proposes new dispersion maps configured by the decaying or expanding distribution of residual dispersion per span (RDPS) in a dispersion-managed link combined with a midway optical phase conjugator. The effect of the proposed dispersion maps on the compensation for distorted 24 channel × 40 Gbps wavelength-division multiplexed signals was assessed through numerical simulation. It was confirmed that all the proposed dispersion maps are most appropriate for the compensation and, furthermore, for the flexibility of link configuration than conventional links.

• 전기의세계
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• v.18 no.5
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• pp.12-19
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• 1969

The sensitivity of transistorized d.c. amplifiers is mainly limited by drift at operating point caused by ambient temperature changes. A chopper-type transistorized amplifier is necessary to obtain a high sensitivity without recourse to drift compensation which requires the adjustment of several balancing controls. A chopper-stabilized system consisting of an electro-mechanical chopper for input and output and a high-gain a.c. amplifier is designed and analyzed. The gain of the a.c. amplifier, expressed as the ratio of voltages, is larger than 80db in the band of 50C/S - 100KC/S. The complete system gives an open-loop gain of 68db at direct current. The offset voltage is 20.mu.V referred in input and the voltage drift at the input is less than 10.mu.V/hr at 25.deg.C. This type of amplifier would be useful for the high-gain transistorized d.c. amplifier for analog computers. Also, due to the high input impedance, it is suitable for amplification of signals from wide range of source impedances.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3230-3232
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• 1999

In this paper describes the design and improvement of a hybrid module for dual slope A/D converter. Since the input voltage to be converted is very sensitive and small. A/D converter must have the temperature stability. low-drift, and the high-resolution the conversion. A dual slop A/D converter circuit which is controlled by microprocessoer has been developed to reduce the offset voltage and the drift characteristics of operation amplifiers, and to improve the A/D conversion speed. Also hybrid module has been adapted to obtain the to obtain the stable and accurate A/D conversion for low cost use. The evaluation of the designed hybrid module has been shown as having a good performance, which will give usefull application to the industrial measurements use.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2327-2329
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• 2005

In this paper, we identify the memory effects of the RF high-power base station amplifiers with Vector Signal Analyzer (VSA). It is found that the model of power- amplifier using Tapped Delayed Neural - Networks with back-propagation algorithm shows very accurate modeling performance. Based on this behavioral modeling, we conducted inverse compensation process which also uses Neural Networks.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3190-3192
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• 1999

A Novel wide-band wide-tunable current-mode (CM) gamma corrector for HDTV camera applications is proposed. The gamma corrector provides accurate gamma control in a wide range by simple electrical adjustment of weighting amplifiers' gain. It has wide signal bandwidth more than 40MHz sufficient for HDTV video signal processing and is implementable with simple integrated circuit with low power dissipation of 125mW.

• Journal of Sensor Science and Technology
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• v.19 no.3
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• pp.230-237
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• 2010

In sensor signal conditioning and processing, offset and drift characteristics of an operational amplifier are an important factor when the amplifier is used for a precise sensor signal amplifier. In order to use it in high accuracy, an expensive trimming or a complex compensation circuit is required. This paper presents the improved sensor signal conditioning and processing device for ubiquitous sensor network(USN) application or general purpose by developing a hardware of the circuit for reducing the offset voltage and drift characteristics, and a software for its control and sensor signal processing. We realize better offset voltage and drift characteristics of the signal conditioning circuit using low cost operational amplifiers. The experimental results show that this technique is effective in improving the performance of the sensor signal processing device.