• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.384-392
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• 2003

In this study, the electromagnetic coupling through a narrow transverse slit in the upper wall of a parallel-plate waveguide(PPW) covered by a dielectric slab with a nearby conducting strip on the slab is considered. Two contrastive coupling phenomena, cavity-type and parasitic-type, observed in the geometry have been distinguished by differences in the resonant strip lengths and offset positions, induced strip current, radiation pattern, frequency bandwidth, and electromagnetic field distributions near the coupling slit.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.227-229
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• 2002

In this paper, we report on a microstrip line voltage controlled tunable bandpass filter. We used the characteristic the relative dielectric constant of thin film ferroelectrics depends on the applied dr voltage. we designed using Au/BSTO/MgO/Au structure. We cascaded many resonators for large furling range sustaining 1 GHz renter frequency, narrow band, low IL ($\leq$4 dB). We could design the BPF of which center frequency is 16 GHz, 1.9 GHz tuning range, the narrow bandwidth within 800 MHz, low insertion loss less than 3 dB by adjusting the gap of 3 cascaded resonators.

• Journal of the Optical Society of Korea
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• v.14 no.1
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• pp.28-32
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• 2010

We demonstrate binary spectral phase coded waveform discrimination at 10 GHz for narrow band optical code-division multiple-access (NB-OCDMA) via direct electrical detection without using any optical hard-limiter. Only 9 phase-locked, 10 GHz spaced, spectral lines within a 100 GHz spectral window are used for the phase coding. Considerably high contrast ratio of 5 between signal and multiuser access interference noise can be achieved for $4{\times}10\;G\;pulse/sec$ timing coordinated OCDMA at a simple electrical receiver with 50 GHz bandwidth.

• The Journal of the Acoustical Society of Korea
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• v.32 no.5
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• pp.377-384
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• 2013

In this paper, performance of COFDM (Coded Orthogonal Frequency Division Multiplexing) which is OFDM with a forward error correction code, is studied in frequency selective fading underwater acoustic communication channel. The OFDM is a multiplexing technique resistant to frequency selective multipath channel. In OFDM, a broadband information signal is transformed into several narrow band signals and transmits narrow band signals whose bandwidths are less than the channel coherence bandwidth. However, its performance is degraded in a specific narrow band signal due to its deep fading by multipath. To mitigate this degradation, COFDM which is OFDM with convolution code as a forward error correction code, is evaluated. The performance of COFDM is found to be better than that of OFDM in multipath channel.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.68-73
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• 2011

In this paper, a compact-narrow open stub band-pass filter with parasitic-signal of low frequency range and second harmonics rejected using the parallel coupled line and FLCLM(Frquency Locked Controlled Length Method) is proposed. The characteristic of the parallel coupled line can be rejection for parasitic-signal of low frequency range and second harmonics. In last filter of experimental results show that insertion loss is 1.2 dB and return loss is 14.8 dB, and the fractional bandwidth is 10 % at the center frequency of 5.8 GHz. In additional, the rejection for parasitic-signal of low frequency range and second harmonics are 28.9 dB and 28.8 dB, respectively.

• Current Optics and Photonics
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• v.4 no.1
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• pp.69-80
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• 2020

A Rayleigh Lidar used for wind detection works by transmitting laser pulses to the atmosphere and receiving backscattering signals from molecules. Because of the weak backscattering signals, a lidar usually uses a high sensitivity photomultiplier as detector and photon counting technology for signal collection. The capturing of returned extremely weak backscattering signals requires the lidar to work on dark background with a long time accumulation to get high signal-to-noise ratio (SNR). Because of the strong solar background during the day, the SNR of lidar during daytime is much lower than that during nighttime, the altitude and accuracy of detection are also restricted greatly. Therefore this article describes an ultra-narrow bandwidth filter (UNBF) that has been developed on 354.7 nm wavelength of laser. The UNBF is used for suppressing the strong solar background that degrades the performance of Rayleigh wind lidar during daytime. The optical structure of UNBF consists of an interference filter (IF), a low resolution Fabry-Perot interferometer (FPI) and a high resolution FPI. The parameters of each optical component of the UNBF are presented in this article. The transmission curve of the aligned UNBF is measured with a tunable laser. Contrasting the result of with-UNBF and with-IF shows that the solar background received by a Licel transient recorder decreases by 50~100 times and that the SNR with-UNBF was improved by 3 times in the altitude range (35 km to 40 km) compared to with-IF at 10:26 to 10:38 on August 29, 2018. By the SNR comparison at four different times of one day, the ratio-values are larger than 1 over the altitude range (25~50 km) in general, the results illustrate that the SNR with-UNBF is better than that with-IF for Rayleigh Lidar during daytime and they demonstrate the effective improvements of solar background restriction of UNBF.

• Journal of Broadcast Engineering
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• v.24 no.1
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• pp.132-141
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• 2019

The necessity of transmitting video data over a narrow-bandwidth exists steadily despite that video service over broadband is common. In this paper, we propose a scalable video coding framework for low-resolution video transmission over a very narrow-bandwidth network by super-resolution of decoded frames of a base layer using a convolutional neural network based super resolution technique to improve the coding efficiency by using it as a prediction for the enhancement layer. In contrast to the conventional scalable high efficiency video coding (SHVC) standard, in which upscaling is performed with a fixed filter, we propose a scalable video coding framework that replaces the existing fixed up-scaling filter by using the trained convolutional neural network for super-resolution. For this, we proposed a neural network structure with skip connection and residual learning technique and trained it according to the application scenario of the video coding framework. For the application scenario where a video whose resolution is $352{\times}288$ and frame rate is 8fps is encoded at 110kbps, the quality of the proposed scalable video coding framework is higher than that of the SHVC framework.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.193-196
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• 2000

In this paper, the performance of DS-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz, 5MHz) and different channel environments (rural, urban). For the analysis of smart antenna system, the vector channel model having the spatio-temporal correlation is needed. Hence, the channel is modeled as a time-variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. A simulation is carried out by dividing several multipaths within one chip into each one and searching the strongest signal. DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.1
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• pp.5-9
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• 2016

The modulation bandwidth of a reflective semiconductor optical amplifier (RSOA) is limited by carrier lifetime. Therefore, it is hard to directly modulate an RSOA with high-speed electrical signals. We theorize that an optical filter can act as an optical equalizer, compensating for the narrow bandwidth limitation imposed by the RSOA. By modeling a time-varying RSOA with a modified transfer matrix method (TMM), we simulated 25 Gbps operation of an RSOA with optical filtering effects. We investigated the impact of detuning the center wavelength of the optical filter on the modulation of an RSOA. The numerical results show that it is possible to modulate an RSOA with an optical filtering effect at 25 Gbps without electronic equalization or digital signal processing.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.79-82
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• 2000

In this paper, the performance of 05-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz, 5MHz) and different channel environments (rural, urban). For the analysis of smart antenna system, the vector channel having the spatio-temporal correlation is modeled as a time-variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. Several multipaths within one chip are distinguished into each one and the strongest signal is selected. DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.