• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.8
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• pp.954-957
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• 2016

In cases of military communication plan, it often requires to find a proper solution for frequency assignment within feasible time. Minimizing the number of used resources are related to cost issue, hence it is a critical objective. When the dual polar antenna is used, the performance can be much developed by exploiting the polarization separation. In this paper, we propose an algorithm that assigns polarizations and frequencies within complexity of $O(N^2)$ based on the graph matching theory. We have verified that the proposed algorithm shows almost twice performance relative to the uni-polar frequency assignment algorithms and it approaches very closely to its theoretical optima.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.913-921
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• 2007

In this paper, we propose a novel small antenna for direction finding applications. The proposed antenna employs a skirt type disk to eliminate the radiation null on the broad-side direction in the high frequency range. Additionally, the multi-section matching stub is used for impedance matching in the low frequency range, The size of the proposed antenna is reduced as a half of the 60cm dipole which has a same resonance frequency of 200MHz. The antenna maintains a donut shape radiation pattern with a broad beam width for a wide range of frequency while the 60cm dipole shows radiation nulls on the broad-side direction and the high side-lobe level from 700MHz to 1,300MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.3
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• pp.209-214
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• 2019

This paper presents the design of a 920 MHz ultra-high frequency(UHF) band radio frequency identification(RFID) conductive fabric tag antenna. The resistance values of four different conductive fabrics are measured, and the conductivities of the fabrics are calculated. The fabric with the best conductivity is selected, and the best conductivity of the fabric is used to simulate the fabric tag antenna design. The fabric UHF RFID tag antenna with a T-Matching structure and name-tag size of $80{\times}40mm$ is simulated and designed. The simulated and measured results are compared, and a laundry test is performed. The reading range of the fabric tag antenna is about 2 m. This fabric tag can be easily applied to an entrance control system as it can be attached to other fabrics and cloths.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.5
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• pp.18-24
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• 2011

In multibit Sigma-Delta Modulator, one of the DEM(Dynamic Element Matching) techniques which is DWA(Data Weighted Averaging) is widely used to get rid of non-linearity caused by mismatching of capacitor that is unit element of feedback DAC. In this paper, by adjusting clock timing used in existing DWA architecture, 2n Register block used for output was replaced with 2n S-R latch block. As a result of this, MOS Tr. can be reduced and extra clock can also be removed. Moreover, two n-bit Register block used to delay n-bit data code is decreased to one n-bit Register. After designing the 3rd 3-bit SC(Switched Capacitor) Sigma-Delta Modulator by using the proposed DWA architecture, 0.1% of mismatching into unit element in input frequency 20 kHz and sampling frequency 2.56 MHz. As a consequence of the simulation, It was able to get the same resolution as the existing architecture and was able to reduce the number of MOS Tr. by 222.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.138-144
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• 2012

In this paper, we introduce the time-domain equalizer in orthogonal frequency division multiplexing (OFDM) systems using orthogonal matching pursuit (OMP) algorithm. Since OFDM system inserts guard intervals, it shows robust performance against multi-path fading. However, in Doppler channel, inter-carrier interference (ICI) occurs because an orthogonality of sub-carriers does not maintain. A least squares (LS) algorithm is common method of time-domain equalizer, but if a channel length is longer, the performance deteriorates by noise. The multi-path fading is a summation of the different delay signal. And that has sparse properties in time-domain. Because the OMP algorithm of the compressive sensing (CS) algorithm restores the channel by choosing the important elements of sparse channel, it can reduce the influence of noise. We simulate the performance of time-domain equalizer in OFDM system with various channel environments using OMP algorithm compared with other equalization method.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.39-45
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• 2018

Compressive sensing allows recovering an original signal which has a small dimension of the signal compared to the dimension of the entire signal in a short period of time through a small number of observations. In this paper, we proposed a method for detecting tonal signal which caused by the machinery component of a vessel such as an engine, gearbox, and support elements. The tonal signal can be modeled as the sparse signal in the frequency domain when it compares to whole spectrum range. Thus, the target tonal signal can be estimated by S-OMP (Simultaneous-Orthogonal Matching Pursuit) which is one of the sparse signal recovery algorithms. In simulation section, we showed that S-OMP algorithm estimated more precise frequencies than the conventional FFT (Fast Fourier Transform) thresholding algorithm in low SNR (Signal to Noise Ratio) region.

• Korean Journal of Remote Sensing
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• v.32 no.6
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• pp.693-701
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• 2016

To make a mosaicked image, we need to estimate the geometric relationship between individual images. For such estimation, we needs tiepoint information. In general, feature-based methods are used to extract tiepoints. However, in the case of textureless images, feature-based methods are hardly applicable. In this paper, we propose a frequency domain matching method for automated mosaicking of textureless images. There are three steps in the proposed method. The first step is to convert color images to grayscale images, remove noise, and extract edges. The second step is to define a Region Of Interest (ROI). The third step is to perform phase correlation between two images and select the point with best correlation as tiepoints. For experiments, we used GOCI image slots and general frame camera images. After the three steps, we produced reliable tiepoints from textureless as well as textured images. We have proved application possibility of the proposed method.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.1
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• pp.47-55
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• 2010

Although heart auscultation is an important tool for the diagnosis of heart disease, it is seen that the human ear is poorly suited for cardiac auscultation such as the paradoxical split of S2, the split of S2, and the summation of S2 and S3 gallop. In this paper, the analysis-synthesis method that is suitable for the characteristics of PCG is proposed to classify the heart sound. In analyzing the PCG according to matching pursuit method and synthesizing the PCG in each bandwidth based on the frequency characteristics, it sorts normal hearts with abnormal hearts that is difficult to classify as cardiac auscultation. The result shows that it qualifies the appearance of split in S2 and the paradoxical split of S2 and also can estimate the delay between the two components.

• Korean Journal of Optics and Photonics
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• v.17 no.2
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• pp.181-185
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• 2006

A novel 60GHz optical carrier generator with a polarization domain-inverted structure is suggested and is demonstrated. The two arms of the Mach-Zehnder optical waveguide are periodically poled for quasi-phase velocity matching between the optical wave at 1550nm and the RF wave at 30 GHz. The center frequency of band-pass modulation and the 3 dB bandwidth of the fabricated modulator were measured to be 30.3 GHz and 5.1 GHz, respectively. Sub-carriers with the frequency difference of 60GHz waeregenerated under appropriate DC biac voltage application while the carrier was suppressed to lead to the power ratio between the modulated sub-carrier and the suppressed fundamental carrier of 28 dB, which proves that double sideband- suppressed carrier(DSB-SC) operation can be realized by the suggested single device.

• Smart Structures and Systems
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• v.25 no.2
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• pp.123-133
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• 2020

Compressive sensing (CS) is a newly developed data acquisition and processing technique that takes advantage of the sparse structure in signals. Normally signals in their primitive space or format are reconstructed from their compressed measurements for further treatments, such as modal analysis for vibration data. This approach causes problems such as leakage, loss of fidelity, etc., and the computation of reconstruction itself is costly as well. Therefore, it is appealing to directly work on the compressed data without prior reconstruction of the original data. In this paper, a direct approach for modal analysis of damped systems is proposed by decomposing the compressed measurements with an appropriate dictionary. The damped free vibration function is adopted to form atoms in the dictionary for the following sparse decomposition. Compared with the normally used Fourier bases, the damped free vibration function spans a space with both the frequency and damping as the control variables. In order to efficiently search the enormous two-dimension dictionary with frequency and damping as variables, a two-step strategy is implemented combined with the Orthogonal Matching Pursuit (OMP) to determine the optimal atom in the dictionary, which greatly reduces the computation of the sparse decomposition. The performance of the proposed method is demonstrated by a numerical and an experimental example, and advantages of the method are revealed by comparison with another such kind method using POD technique.