• Journal of IKEEE
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• v.20 no.3
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• pp.318-321
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• 2016

As IoT industry are growing fast, The importance of power management system is also being magnified. CMOS High power-supply rejection ratio(PSRR) Low-dropout(LDO) regulator is achieved by the proposed ripple Subtractor, Feed-forward capacitor and OTA in this paper. The LDO is implemented in $0.18-{\mu}m$ CMOS technology. With the proposed structures, in the maximum loading of 40mA, Simulation result achieves PSRR of -73.4dB at 500kHz and PSRR better than -40dB when frequency is below 10MHz with $6.8-{\mu}F$ output capacitor.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.425-431
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• 2023

An asymmetric metal-semiconductor-metal Al_0.24Ga_0.76N ultraviolet (UV) sensor was fabricated, and the effects of local Joule heating were investigated. After dielectric breakdown, the current density under a reverse bias of 2.0 V was 1.1×10^-9 A/cm², significantly lower than 1.2×10^-8 A/cm² before dielectric breakdown; moreover, the Schottky behavior of the Ti/Al/Ni/Au electrode changed to ohmic behavior under forward bias. The UV-to-visible rejection ratio (UVRR) under a reverse bias of 7.0 V before dielectric breakdown was 87; however, this UVRR significantly increased to 578, in addition to providing highly reliable responsivity. Transmission electron microscopy revealed interdiffusion between adjacent layers, with nitrogen vacancies possibly formed owing to local Joule heating at the AlGaN/Ti/Al/Ni/Au interfaces. X-ray photoelectron microscopy results revealed decreases in the peak intensities of the O 1s binding energies associated with the Ga-O bond and OH-, which act as electron-trapping states on the AlGaN surface. The reduction in dark current owing to the proposed local heating method is expected to increase the sensing performance of UV optoelectronic integrated devices, such as active-pixel UV image sensors.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.11
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• pp.9-15
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• 2004

We propose optimal interference rejection weight for multistage parallel nulling (MPN) partial parallel interference cancellation (PPIC) receiver previously proposed to enhance the performance of V-BLAST for downlink multiple-input multiple-output (MIMO) multicarrier (MC)-code division multiple access (CDMA) systems. MPN-PPIC method proposed in [1] was based on the parallel interference cancellation (PIC) with fixed interference rejection weight obtained experimentally. However, the fixed weight can not be adapted to various systems efficiently, thus we proposed method for the optimal interference rejection weight based on the received signal to interference and noise ratio (SINR), and the performance of the proposed method was evaluated through computer simulation comparing with the previous method. We obtained performance gains of 2.5 dB ~ 5 dB for BER of 10$^{-3}$ .

• Journal of Korea Multimedia Society
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• v.11 no.11
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• pp.1471-1479
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• 2008

In this paper, we propose a technique to improve Out-Of-Vocabulary(OOV) rejection algorithms in variable vocabulary recognition system which is much used in ASR(Automatic Speech Recognition). The rejection system can be classified into two categories by their implementation method, keyword spotting method and utterance verification method. The utterance verification method uses the likelihood ratio of each phoneme Viterbi score relative to anti-phoneme score for deciding OOV. In this paper, we add speaker verification system before utterance verification and calculate an speaker verification probability. The obtained speaker verification probability is applied for determining the proposed variable-confidence threshold. Using the proposed method, we achieve the significant performance improvement; CA(Correctly Accepted for keyword) 94.23%, CR(Correctly Rejected for out-of-vocabulary) 95.11% in office environment, and CA 91.14%, CR 92.74% in noisy environment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.34-40
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• 2011

From the present paper researched about the Design of Image Rejection SSB Modulator for X-Band Monopulse RADAR using Waveguide Hybrid Coupler. Generally, SSB modulator mixes IF(RF) and LO signals, and then it converts to RF(IF) frequency band. In this case, in order to transmit one sideband from RF band, SSB modulator is demanded the removal of image and LO signal. The balanced mixer was designed using waveguide hybrid coupler and crystal mixer diode to mix LO and IF signal. And also the IF Amplifier was designed for IF(+) and IF(-) signal generation which have $90^{\circ}$ phase differences which are suitable in two crystal mixer diode inputs. In order to maintain a high electric reliability from high frequency band the waveguide and IF amplifier's case were manufactured with aluminum using deep brazing techniques. The test result of SSB modulator, LO and sideband signal rejection ratio were 14.2dB and 18.5dB respectively.

• Journal of IKEEE
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• v.20 no.1
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• pp.68-74
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• 2016

In this paper, we present a compact planar dual band rejection Ultra Wide Band(UWB) antenna with folded parasitic element. The proposed antenna is consist of a hexagonal planar radiation patch antenna with a folded parasitic element which is located over the top and bottom surface. In contrast with other antenna which rejects single band using one method, folded parasitic element rejects dual band using one simple structure. Owing to folded parasitic element, dual-rejected properties are achieved in the Worldwide Interoperability for Microwave Access(WiMAX), C-band, and Wireless Local Area Network(WLAN) bands. The bandwidth of the proposed antenna was measured as 3.1~10.6 GHz for voltage standing wave ratio(VSWR) less than 2, except for the dual rejection bands of 3.4~4.2 GHz and 5.15~6.00 GHz.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.1
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• pp.49-58
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• 1997

In this paper, a transfer function was obtained for a PWM high speed solenoid valve controlled metal belt CVT system. The transfer function was defined as the ratio of speed ratio to PWM duty ratio and derived in time domain by linear regression analysis from the experimental results. The transfer function obtained showed different dynamic characteristics for the up and down shift. Also, LQG/LTR controller was designed for the CVT system using the transfer function. It is seen from the experimental results that LQG/LTR control showed good performance for the speed ratio tracking and disturbance rejection. The phase difference and relatively slow response are considered due to the inaccuracy os the transfer functions, which resulted from the inherent nonlinearities of the transmission characteristics of the metal belt CVT.

• Environmental Engineering Research
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• v.16 no.1
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• pp.29-34
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• 2011

The electric charge on a membrane was investigated by analyzing the experimental rejection of various monovalent and divalent ionic solutes. The characteristics of the separation of ionic solutes using various nanofiltration membranes were obtained from an experimental nanofiltration set-up, with a surface area of $40cm^2$ under the operational pressures between 0.25-0.3 MPa. The state of the membrane electric charge was observed using separation coefficients, i.e., the permeation ratio of monovalent to divalent ions. To confirm the state of the membrane charge observed via the separation coefficient, a calculation using the extended Nernst-Planck equation, coupled with the Donnan equilibrium, assuming different electric charge states of the membrane, was compared with the experimental rejection of ionic solutes. The examination of the characteristics of separation using three types of nanofiltration membranes showed that one of the membranes carried a negative/positive double charge density inside, while other two membranes carried either a positive or negative charge density.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.5-8
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• 1999

In this paper, we present narrowband interference (NBI) cancelling algorithm applied to wideband spread spectrum system. We introduce multi-carrier transmission technique to overcome hardware inplementation difficulty of wideband spreading above 40MHz and to enhance NBI performance. A direct-sequence spread spectrum receiver using both decision-feedback and two sided LMS filters for combating narrowband interference is applied. We show that performance of this receiver outperforms conventional NBI rejection systems in tone jamming, partial band jamming, and impulsive channel through the bit error ratio evaluation. In addition, we propose a new technique to improve the performance of time domain NBI rejection algorithm sensitive to impulsive channel.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1977-1978
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• 2008

In this paper, we compare performance of common-mode rejection between a differential and a non-differential amplifier system with two electrodes. A differential amplifier system is constant for common-mode rejection ratio(CMRR) on the frequency domain. But a non-differential amplifier's CMRR is determined by $Z_{FB}/Z_e$ ($Z_{FB}$ ; feedback impedance, $Z_e$; electrode impedance). There is trade-off between a non-differential amplifier's CMRR and its differential input impedance. And a non-differential amplifier system has some advantages for a bio-potential measurement with two electrodes because a designer can control the impedance between the body and system's common.