• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.6
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• pp.1522-1532
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• 1996

In this paper, we compare the performance of channel estimators with the L$_{1}$-norm and L$_{2}$-norm criteria in impulaive noise environment, and show than the L$_{1}$-norm criterion is appropriate for that situation. Also, it is shown that the performance of the conventional maximum likelihood sequence detector(MLSD) can be improved by applying the same principle to mobile channels. That is, the performance of the conventional MLSD, which is known to be optimal under the Gaussian noise assumption, degrades in the impulsive noise of radio mobile communication channels. So, we proposed the MLSD which can reduce the effect of impulsive noise effectively by applying the results of channel estimators. Finally, it is confirmed by computer simulation that the performance of MLSD is significantly affected depending on the types of branch metrics, and that, in the impulsive noise environments, the proposed one with new branch metrics performs better thatn the conventional branch metric, l y(k)-s(k) l$^{[-992]}$ .

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.949-955
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• 1997

Detection of the existence of a desired user is considered in this paper. We assume that the signal to noise ratio is high enough for us to ignore the effects of noise compared with those of the interference by other users. The inter-user interference and user signals are modeled by the Nakagami model. An observation model for this situation is proposed, the locally optimum test statistic is derived under the model, and the asymptotic performance of the locally optimum detector is compared with of the envelope detector. We show that the locally optimum detector performs better than the conventional envelope detector.

• 전자공학회논문지 IE
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• v.43 no.2
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• pp.75-79
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• 2006

Blind techniques without the help of training sequences are able to detect the information signal which has the minimal information of desired user. In this paper, we proposed the blind multiuser detector using the hybrid cost function to cancel the multiple user interference in direct sequence code division multiple access systems. The cost function of proposed blind multiuser detector is the hybrid type which joints both least mean square(LMS) algorithm and least mean fourth(LMF) algorithm. We evaluate the bit error rate(BER) performance of proposed blind multiuser detector under additive white Gaussian noise channel. Simulation results show that the proposed blind detector has an about 3dB of signal to noise ratio more than blind minimum output energy(MOE) multiuser detector under existing active user 20.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.842-850
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• 2018

In this paper, the design and fabrication of a frequency-locked-loop(FLL) 5-GHz oscillator with a single resonator is presented. The proposed oscillator is the simplified version of the previous FLL oscillator with two separate resonators in the VCO and frequency detector. The resonator is commonly used in the VCO and frequency detector of the proposed oscillator configuration. The 5-GHz oscillator is implemented on the hetero-multilayer substrate composed of a Rogers' RO4350B laminate, which has excellent high-frequency performance, and the commercial FR4 three-layer substrate. The frequency locking occurs at approximately 5 GHz and has an output power of 3.8 dBm. The phase noise has a free-run VCO phase noise at frequencies above 1 kHz, and an FLL background noise at frequencies below 1 kHz. For this loop-filter, the phase noise showed an improvement of approximately 12 dB at the offset-frequency of 100 Hz.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.633-636
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• 2005

An electro-optical camera system consists of many subsystems such as the optics, the detector, and the electronics and so on. They may create variations in the processed image that were not present original scene. The performance analysis of the electro-optical camera system is a mathematical construct that provides an optimum design through appropriate trade off analysis. The SNR(Signal to Noise Ratio) is one of the most important performance for the electro-optical camera system. The SNR analysis shown in this paper is performed based on the practical high resolution satellite camera design. For the purpose of the practical camera design, the analysis assumes that the defined radiance, which is calculated for the Korean peninsula, reached directly to the telescope entrance. In addition, the actual operation concept such as integration time and the normal operation altitude is assumed. This paper compares the SNR analysis results according to the various camera characteristics such as the optics, the detector, and the camera electronics. In detail, the optical characteristics can be split into the focal length, F#, transmittance, and so on. And the system responsivity, the quantum efficiency, the TDI stages, the quantization noise and the analogue noise can be used for the detector and the camera electronics characteristics. Finally this paper suggests the optimum design to apply the practical electro-optical system.

• Nuclear Engineering and Technology
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• v.56 no.6
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• pp.2057-2062
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• 2024

Among photon counting detector (PCD)-based technologies, the K-edge subtraction (KES) method has a very high material decomposition efficiency. Yet, since the increase in noise in the X-ray image to which the KES method is applied is inevitable, research on image quality improvement is essential. Here, we modeled a block-matching and 3D filtering (BM3D) algorithm and applied it to PCD-based X-ray images with the improved KES (IKES) method. For PCD modeling, Monte Carlo simulation was used, and a phantom composed of iodine substances with different concentrations was designed. The IKES method was modeled by adding a log term to KES, and the X-ray image used for subtraction was obtained by applying the 3.0 keV range based on the K-edge region of iodine. As a result, the IKES image using the BM3D algorithm showed the lowest normalized noise power spectrum value. In addition, we confirmed that the contrast-to-noise ratio and no-reference-based evaluation results when the BM3D algorithm was applied to the IKES image were improved by 29.36 % and 20.56 %, respectively, compared to the noisy image. In conclusion, we demonstrated that the IKES imaging technique using a PCD-based detector and the BM3D algorithm fusion technique were very efficient for X-ray imaging.

• The Korean Journal of Applied Statistics
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• v.32 no.5
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• pp.721-740
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• 2019

Noise reduction is an important field in image processing and requires a statistical approach. However, it is difficult to assume a specific distribution of noise, and a spatial filter that reflects regional characteristics is a small sample and cannot be accessed in a parametric manner. The first order image differential and the second order image differential show a clear difference according to the noise level included in the image and can be more clearly understood using the canyon edge detector. The Fligner-Killeen test was performed and the bootstrap method was used to statistically check the noise level. The estimated noise level was set between 0 and 1 using the cumulative distribution function of the beta distribution. In this paper, we propose a nonparametric noise reduction algorithm that accounts for the noise level included in the image.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.10
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• pp.8-13
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• 2009

The MF(matched filter) is the optimum signal detector that maximizes the output instantaneous signal power to average noise power ratio in white noise environment. But it cannot give the optimum detection performance if the background noise is not white. So, the whitening process preceding the matched filter is needed in the conventional detector which results in a PWMF(pre-whitening matched filter). Its performance is mainly affected by the estimation accuracy of non-white noise model which is used in the whitening procedure. To estimate more accurate model to improve performance, the computational complexity is increased. Therefore, a spectrum based detector which shows better performance than the PWMF under the similar complexity condition or less complexity under the similar performance condition is proposed in this paper. And its performance and complexity are analyzed and compared with the conventional PWMF.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1643-1647
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• 2003

This paper, we propose a new high noise immunity phase-locked loop(PLL) which can suppress the high incident noise coupling with large amplitude and long period to the input frequency of PLL and keeps constant frequency and phase of the VCO output for providing the high stability distribution clock pulse.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.6
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• pp.865-870
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• 2001

In this paper, we analyse the effect of phase noise from PLL frequency synthesizer on 64 QAM when detecting corrupted signals. To predict the phase noise of an oscillator very accurately, we assume that the oscillator is linearly time-varying when the input impulsive current to the oscillator is small. The performance of the detector which detects the corrupted signal by oscillator phase noise is compared with that when the detector is only affected by AWGN and then analyse how much the phase noise degrades the system performance for 64 QAM.