• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.105-110
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• 2007

A tunable band-pass filter of fiber Bragg gratings incorporating the Sagnac loop interferometer configuration is presented. The proposed band-pass filter with extinction ratio 20 dB has practical advantages in terms of price and performance in comparison with the conventional band-pass filter using a circulator.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.3
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• pp.141-144
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• 2015

A broadband radio frequency synthesizer for multi-band, multi-standard mobile DTV tuners is proposed, it's loop bandwidth can be calibrated to optimize integrated phase noise performance without the problem of phase noise peaking. For this purpose, we proposed a new third-order scalable loop filter and a scalable charge pump circuit to minimize the variation in phase margin during calibration. The prototype phase-lock loop is fabricated in 180nm complementary metal-oxide semiconductor shows that it effectively prevents phase noise peaking from growing while the loop bandwidth increases by up to three times.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.6
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• pp.8-15
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• 2012

In this paper, we investigated possible optical parameters causing deviation of experimentally observed output spectra from theoretically predicted results in a high-order fiber comb filter based on a polarization-diversity loop configuration. They include wavelength dependency of half-wave plates (HWPs) inserted in the filter for wavelength switching and the modal birefringence of single-mode fibers (SMFs) with which optical components comprising the filter are connected. In order to consider the effect of the modal birefringence of the SMF on a filter performance, it is modeled as a low birefringence fiber with an arbitrary orientation angle and birefringence. It is found from the simulation results that the modal birefringence of SMFs strongly affects the spectral characteristics of the filter and decreases the extinction ratio of the filter, compared with the wavelength dependency of HWPs. In particular, it is also confirmed that the spectral deviation and asymmetric distortions of side-lobes in narrow band transmission spectra result mainly from the modal birefringence of SMFs.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.3
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• pp.107-110
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• 2009

In this paper, a PN code tracking loop with extended Kalman filter (EKF) is proposed for a direct-sequence spread-spectrum. EKF is used to estimate amplitude and delay in a multipath. fading channel. It is shown that tracking error performance is significantly improved by EKF compared with a conventional tracking loop.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.112-114
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• 2009

In this paper, a PN code tracking loop with extended Kalman filter (EKF) is proposed for a direct-sequence spread-spectrum. EKF is used to estimate amplitude and delay in a multipath fading channel. It is shown that tracking error performance is significantly improved by EKF compared with a conventional tracking loop.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.1-13
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• 2011

In this paper, we propose an adaptive in-loop filter to improve the coding efficiency. Recently, there are post-filter hint SEI and block-based adaptive filter control (BAFC) methods based on the Wiener filter which can minimize the mean square error between the input image and the decoded image in video coding standards. However, since the post-filter hint SEI is applied only to the output image, it cannot reduce the prediction errors of the subsequent frames. Because BAFC is also conducted with a deblocking filter, independently, it has a problem of high computational complexity on the encoder and decoder sides. In this paper, we propose the low-complexity adaptive in-loop filter (LCALF) which has lower computational complexity by using H.264/AVC deblocking filter, adaptively, as well as shows better performance than the conventional method. In the experimental results, the computational complexity of the proposed method is reduced about 22% than the conventional method. Furthermore, the coding efficiency of the proposed method is about 1% better than the BAFC.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.1
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• pp.74-81
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• 2014

This article documents the design of a novel two-loop acceleration autopilot based on $\mathcal{L}_1$ adaptive output feedback control for tail-controlled missiles. The inner loop is an adaptive angle-of-attack tracking loop and the outer loop is the traditional PI controller for error compensation. A systematic low-pass filter design procedure is provided for minimum phase system and is applied to the inner loop design while the parameters of the outer loop are obtained from the multi-objective optimization problem. The effectiveness of the proposed autopilot is verified through numerical simulations under various conditions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.8
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• pp.1068-1075
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• 2018

In this paper, a novel PLL has been proposed that reduces the size of the loop filter while suppressing spur by using a VCO with two inputs. Through the stability analysis according to the operating status, the PLL is designed to operate stably after the phase fixing. The capacitor of loop filter usually occupies larger area of PLL. It is a VCO that can reduce the size of the loop filter by increasing the effective capacitance of the capacitor through the simultaneous charge and discharge operation by two charge pumps and has two signals operating in opposite phases. The settling time of set to $80{\mu}s$ approximately by using a LSI(Locking Status Indicator) indicating the phase locking status. The proposed PLL is designed using a supply voltage of 1.8V and a $0.18{\mu}m$ CMOS process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.2
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• pp.339-344
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• 2017

A novel structure of phase locked loop (PLL) which has small size and fast locking time with Early-late detector, Duty-rate modulator, and Lock status indicator (LSI) is proposed in this paper. The area of loop filter usually occupying the larger portion of the chip is minimized using a single small capacitor. While the conventional PLL with a single capacitor loop filter cannot work stably, the proposed PLL with two charge pumps works stably because the output voltage waveform of the proposed a single capacitor loop filter is the same as the output voltage waveform of the conventional 2nd-order loop filter. The two charge pumps are controlled by the Early-late detector which detects early-late status of UP and DN signals, and Duty-rate modulator which generates a steady duty-rate signal. Fast locking time is achieved using LSI. It has been simulated and proved by HSPICE in a CMOS $0.18{\mu}m$ 1.8V process.

• Journal of electromagnetic engineering and science
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• v.17 no.4
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• pp.197-201
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• 2017

In this paper, we present a novel design for a dual-band bandpass filter (BPF) based on the conventional second-order, open-loop BPF. By adding series resonant circuits to the open ends of the resonator, we can create two resonant modes from the even and odd modes. One pair of the even and odd modes constitutes the upper passband, while the other pair constitutes the lower passband. By adding another series resonant circuit to the open-loop resonator, we can control the bandwidth of either the upper passband or the lower passband. We can replace the series resonant circuits with simple microstrip line resonators. A dual-band BPF working at both Wi-Fi bands (2.4 GHz and 5.8 GHz bands) is designed based on the proposed method and is tested. The measured and simulated results show excellent agreement.