• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.15-20
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• 2013

In narrowband communication systems operating in VHF and UHF bands, the performance degradation due to a frequency offset is inevitable. In this paper, we propose a frequency offset reduction scheme using the dual-band FSK modulation for narrowband communications. The proposed scheme not only offer a relatively reliable performance under a severe frequency offsets, but also can obtain a frequency diversity gain in Rayleigh fading channel.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.523-526
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• 2002

This paper presents the simulation of Au / $Ba_{x}$S $r_{1-x}$ Ti $O_3$(BSTO) / Magnesium oxide (MgO) multi-layered and electrically tunable band-pass filters (BPFs) by using high frequency structure simulator (HFSS). This model is a two-pole microstrip edge coupled filter. The filter was designed fur a center frequency about 5.8 GHz. The tunabillity of the filter is achieved using the nonlinear dc electric-field dependence on the relative dielectric constant of BSTO frroelectric thin film. This work seems very promising for future wireless communication systems....

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.166-171
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• 2012

In this paper, short-range underwater wireless communication technique using visible LEDs is proposed. As an alternative to conventional acoustic system, visible LED communications show high quality and high speed data transmission characteristics. We design a frequency modulation-based optical wireless audio transmission system. The CD4046B phase-locked loop device is applied to implement the frequency modulation and demodulation. With a transmission modulation of 100 kHz, audio signal has successfully received at a transmission distance of 30 cm.

• ETRI Journal
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• v.37 no.6
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• pp.1055-1064
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• 2015

We demonstrate a next-generation high-capacity mobile fronthaul based on radio over fiber (RoF) technology, which links between a digital unit and a radio unit supporting two frequency assignments and $2{\times}2$ multiple input, multiple output antennas. To confirm the technical feasibility of a mobile fronthaul, we experimentally investigate its down- and uplink end-to-end performances including the optical and radio frequency (RF) signal path. Frequency-dependent performance deviations, error vector magnitude variations, overall system performance variations caused by optical to electrical conversion, and intermediate frequency to RF conversions are examined. Experimental verifications on multiple LTE uplink signals are performed for the first time. We also demonstrate several commercial mobile Internet services, YouTube video streaming, and file transfers using off-the-shelf mobile devices, through a mobile fronthaul based on RoF.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.1
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• pp.44-50
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• 2015

This paper presents a high speed synchronous single inductor dual output boost converter using Type-III compensation for power management in smart devices. Maintaining multiple outputs from a single inductor is becoming very important because of inductor the sizes. The uses of high switching frequency, inductor and capacitor sizes are reduced. Owing to synchronous rectification this kind of converter is suitable for SoC. The phase is controlled in time sharing manner for each output. The controller used here is Type-III, which ensures quick settling time and high stability. The outputs are stable within $58{\mu}s$. The simulation results show that the proposed scheme achieves a better overall performance. The input voltage is 1.8V, switching frequency is 5MHz, and the inductor used is 600nH. The output voltages and powers are 2.6V& 3.3V and 147mW &, 230mW respectively.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.164-168
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• 2016

A dual-band through-the-wall imaging radar receiver for a frequency-modulated continuous-wave radar system was designed and fabricated. The operating frequency bands of the receiver are S-band (2-4 GHz) and X-band (8-12 GHz). If the target is behind a wall, wall-reflected waves are rejected by a reconfigurable $G_m-C$ high-pass filter. The filter is designed using a high-order admittance synthesis method, and consists of transconductor circuits and capacitors. The cutoff frequency of the filter can be tuned by changing the reference current. The receiver system is fabricated on a printed circuit board using commercial devices. Measurements show 44.3 dB gain and 3.7 dB noise figure for the S-band input, and 58 dB gain and 3.02 dB noise figure for the X-band input. The cutoff frequency of the filter can be tuned from 0.7 MHz to 2.4 MHz.

• Journal of the Semiconductor & Display Technology
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• v.9 no.2
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• pp.7-10
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• 2010

In this paper, we design a modem SoC (System on Chip) for low power consumption and high speed wireless communications. Among various schemes of high speed communications, an MB-OFDM (Multi Band-Orthogonal Frequency Division Multiplexing) UWB (Ultra-Wide-Band) chip is designed. The MB-OFDM uses wide-band frequency to provide high speed data rate. Additionally, the system imposes no interference to other services. The 90nm CMOS (Complementary Metal-Oxide Semiconductor) technology is used for the SoC design. Especially, power management mode is implemented to reduce the power consumption.

• Journal of Broadcast Engineering
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• v.17 no.3
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• pp.459-470
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• 2012

In this paper, we propose a method to upsample a low-resolution depth map to a high-resolution version. While conventional camera sensors produce high-resolution color images, the sizes of the depth maps of range/depth sensors are usually low. In this paper, we consider the utilization of high-frequency components to the conventional depth map interpolation methods such as bilinear, bicubic, and bilateral. The proposed method is composed of the three steps: high-frequency component extraction, high-frequency component application, and interpolation. Two objective evaluation measures such as sharpness degree and blur metric are used to examine the performance. Experimental results show that the proposed method significantly outperforms other conventional methods by a factor of 2 in terms of sharpness degree. As well, a blur metric is reduced by a factor of 14 %.

• Current Optics and Photonics
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• v.2 no.1
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• pp.53-58
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• 2018

A novel X-band high speed frequency sweep signal generator based on a tunable optoelectronic oscillator (OEO) incorporating a frequency-swept laser is presented and the theoretical fundamentals of the design are explained. A prototype of the generator with tuning range from 8.8552 GHz to 10.3992 GHz and a fine step about 8 MHz is achieved. The generated radiofrequency signal with a single sideband (SSB) phase noise lower than -100 dBc/Hz@10KHz is experimentally demonstrated within the whole tunable range, without any narrow RF band-pass filters in the loop. And the tuning speed of the frequency sweep signal generator can reach to over 1 GHz/s benefiting from applying a novel dispersion compensation modular instead of several tens of kilometers of optical fiber delay line in the system.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.366-370
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• 2007

This paper discusses a most suitable wireless communications system for subway trains on condition that a geo-spatial video system is implemented in subway trains. Geo-spatial video system for subway trains refers to the device that can transfers the images captured by cameras within a subway station building or in and around a subway track to on coming trains wirelessly, which allows the operator in operating room to monitor the state of a platform and a subway track, the flow of passengers, and the condition of passengers getting on and off. To minimize the problem, secure civil safety and prevent accidents and calamity from occurring, a geo-spatial video system for subway trains has been increasingly introduced. The wireless communications systems for GVS for subway trains involve HF(High Frequency), IR(Infra Red), M/W(Micro Wave), wireless LAN approaches. Each has its own strengths/weaknesses, and different vendors have different technology.