• IEMEK Journal of Embedded Systems and Applications
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• v.7 no.2
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• pp.85-93
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• 2012

In this paper, we proposed Wireless LAN (WLAN) localization method that enhances database construction based on weighting factor and analyse the characteristic of the WLAN received signals. The weighting factor plays a key role as it determines the importance of Received Signal Strength Indication (RSSI) value from number of received signals (frequency). The fingerprint method is the most widely used method in WLAN-based positioning methods because it has high location accuracy compare to other indoor positioning methods. The fingerprint method has different location accuracies which depend on training phase and positioning phase. In training phase, intensity of RSSI is measured under the various. Conventional systems adapt average of RSSI samples in a database construction, which is not quite accurate due to variety of RSSI samples. In this paper, we analyse WLAN RSSI characteristic from anechoic chamber test, and analyze the causes of various distributions of RSSI and its influence on location accuracy in indoor environments. In addition, we proposed enhanced weighting factor algorithm for accurate database construction and compare location accuracy of proposed algorithm with conventional algorithm by computer simulations and tests.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.2
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• pp.39-45
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• 2002

A new EMI estimation technique concerned with a PDP system is presented. A physical circuit model is developed which can fairly well describe the AC-PDP system. EMIs of the PDP system are quantitatively determined by combining circuit model and Hertzian dipole antenna model. The simulation results are experimentally verified with the test panel. The AC PDP system was measured in the frequency range of 30MHz~300MHz in a semi-anechoic chamber, according to CISPR 13 code. Thereby, it is shown that the proposed technique can be usefully employed for EMI reduction.

• Proceedings of KOSOMES biannual meeting
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• 2003.05a
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• pp.135-139
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• 2003

This paper describes on the development of Passive-type Radar Reflector for Fisheries (PRR-F) based on the newly revised 2000 SOLAS regulations. The purpose of PRR-F is to provide it as the protection devices of a fishing net and a fishing field. The PRR-F is composed of corner cluster bundle of light galvanized iron, and it is inserted into floating styrofoam. Performance tests for the PRR-F are carried out in an anechoic chamber. The test results show that the reflected radar signal from PRR-F is large enough for the purpose.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.6
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• pp.598-605
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• 2008

An improved beamforming method is proposed to measure the surface impedance of absorbing materials in a free field. It is possible to estimate the surface impedance by decomposing measured signals into incident and reflected signals by using the spatial filter matrix of the beamforming method. Wavelet do-noising techniques which reduce the white Gaussian noise are applied to improve the results. Phase calibration method is also used to improve the results of the measured surface impedance in a low frequency range. The results of the normal incidence experiments that are performed in a semi-anechoic chamber are verified by comparing with those of the standard test method that is presented in ASTM E1050. The proposed method is found to be reliable to measure the surface impedance for frequencies higher than 400 Hz.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.736-740
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• 2007

A laboratory study on low frequency noise assessment has been carried out to evaluate the relevance of the weighting curve. Especially, the A-weighting curve which is used in most noise assessments has been evaluated using the acceptability limit in this study. The acceptability limit is one of the indicators in which the subjective responses were well-reflected. For the measurement of the acceptability limit, pure tone stimuli were used in the frequency range between 20 and 200 Hz. The measurement was proceeded in the anechoic chamber to minimize the background noise level. A total of 29 test subjects, who were aged between 19 to 33 years, participated in this study. They had been exposed to various stimuli for about 1 hour by supra-aural earphone. The measurement consisted of two listening sessions: hearing threshold and the acceptability limit session. The results showed that the tendency of the acceptability limit curve was approximately equal to C-weighting curve which had been found to be superior to A-weighting curve in assessment of low frequencies.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.389-395
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• 2012

In this paper, we analyzed the frequency spectrum of the electromagnetic waves radiated by an electric discharge as a basic study to develop an on-line diagnostic technique for power equipment installed inside closed-switchboards. In order to simulate local and series arc discharges caused by an electric field concentration and poor connections, three types of electrode systems were fabricated, consisting of needle and plane electrodes and an arc generator meeting the specifications of UL 1699. The experiment was carried out in an electromagnetic anechoic chamber, and the measurement system consisted of a PD free transformer, a loop antenna with a frequency bandwidth of 150 kHz-30 MHz, an ultra log periodic antenna with a frequency bandwidth of 30 MHz-2 GHz, and an EMI test receiver with a frequency bandwidth of 3 Hz-3 GHz. According to the experimental results, the frequency spectra of the electrical discharges were widely distributed across a range of 150 kHz-400 MHz, depending on the defects, while commonly found between 150 kHz and 10 MHz. Therefore, considering the ambient noise and antenna characteristics, the best frequency bandwidth for a measurement system to monitor abnormal conditions by detecting electromagnetic waves in closedswitchboards is 150 kHz-10 MHz.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.8 s.113
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• pp.797-805
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• 2006

The sound quality characteristics of refrigerator noise in an anechoic chamber and in a real living environment for 30 models of refrigerators were investigated. Subjective evaluation experiments were conducted to determine subjective tolerance level for refrigerator noise. Refrigerator noise was played from a loudspeaker at the position normally occupied by a refrigerator in a real living environment. A nine-point scale was used to measure subjective satisfaction of the sound pressure levels for refrigerator noise. Point 3 on the scale corresponded to a sound pressure level of about 30 dB(A). Seventy percent of the participants were satisfied with this level of refrigerator noise. A semantic differential test was also conducted to evaluate the sound quality of refrigerator noise. From the results of correlation and multiple regression analyses on the psychoacoustical parameters and subjective evaluations of 30 refrigerators, sound quality indices which predict the subjective rating score were proposed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.157-163
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• 2019

A small millimeter-wave tracking radar is a pulse radar that searches, detects, and tracks a target in real time through a TWS (Track While Scan) method on a sea-going traps target with a large RCS running at low speed. This paper describes the development of a simulated signal generator to verify the performance of a small millimeter wave tracking radar in laboratory anechoic chamber environment. We describe a GUI program for testing and performance analysis in conjunction with hardware configuration and tracking radar, and verified the simulated signal generator implemented through performance test.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.4
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• pp.35-40
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• 2023

For the EMC test, the radiation characteristics and immunity characteristics of the EUT are measured under the condition that the EUT maintains its normal operation. For normal operation of the EUT, it is necessary to operate the EUT and monitor its status through separate equipment outside the anechoic chamber. External equipment operates and monitors the EUT through various communications such as 1553B communication, RS-485 communication, and Ethernet communication. At this time, external equipment can transmit noise through the communication line. This noise is transmitted to the LISN through the connected power cable and measured. It is also radiated through the connection terminal to the LISN. In this case, the communication line is the power line It should be designed so that noise is not transmitted through electromagnetic isolation as much as possible. In addition, noise from external equipment must be suppressed as much as possible from entering the chamber through the communication line. In this paper, external EUT test equipment applied for EMC test It explains the considerations in the design and manufacture of the design and explains the satisfaction of the design through tests including CE and RE.

• Proceedings of KOSOMES biannual meeting
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• 2003.05a
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• pp.125-134
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• 2003

This paper describes on the design of Passive-type Radar Reflector for small Ship (PRR-S) based on the newly revised 2000 SOLAS regulations. The design idea, adopted in the study, is to hold PRR-S in the proper ‘catch rain’ position to avoid fluctuations of Radar Cross Section (RCS) due to ship's heeling. The PRR-S consists of octahedral-type radar reflector with circular plates and three-axis gimbaled stabilizer with weight on the bottom of outer gimbal ring. Performance test for the PRR is carried out in an anechoic chamber. The test results show that the reflected radar signal from PRR-S is more uniformly distributed than the reference model (Davis Echomaster).