• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.12
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• pp.1097-1104
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• 2016

The infrared camera is difficult to satisfy the RE-102 specification of Mil-Std-461. Especially, in the case of UAV electronics, shielded cable is not used, so it is difficult to meet the electromagnetic compatibility standard. In the RE-102 test of the IR camera for UAV, radiated noise exceeding 30 dBuV/m was observed in the range of 50 MHz to 200 MHz. As a result of pcb em scan, peak noise which caused by the harmonic frequency of the digital control signal clock was observed. Radiated noise was reduced by up to 22.9 dBuV/m by applying the spread spectrum clock generator(SSCG) with 3 % down spreading method to the camera control clock.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.61-67
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• 2006

This paper proposes the algorithm for tracking of the residual phase errors incurred by carrier frequency offset and sampling frequency offset in the orthogonal frequency division multiplexing (OFDM) systems which are suitable for high data rate wireless communications. In the OFDM systems the subcarriers which are orthogonal to each other are modulated by digital data and transmitted simultaneously. The carrier frequency offset causes degradation of signal to noise ratio(SNR) performance and interference between the adjacent subcarriers. The errors in the sampling timing caused by the sampling frequency difference between the transmitter and the receiver sides also cause a major performance degradation in the OFDM systems. The residual error tracking and compensation mechanism is essential in the OFDM system since the carrier and the sampling frequency offset cause the loss of orthogonality resulting in the system performance loss. This paper proposes the scheme where the channel gain and the payload data information are reflected in the residual error tracking process which results in the reduction of the estimation error and the tracking performance improvements under the frequency selective fading wireless channels.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.815-821
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• 2009

Information processing in variable and noisy environments is usually accomplished by means of adaptive filters. Among various adaptive algorithms, Least Mean Square (LMS) has become the most popular for its robustness, good tracking capabilities and simplicity, both in terms of computational load and easiness of implementation. In practical application of the LMS algorithm, the most important key parameter is the Step Size. As is well known, if the Step Size is large, the convergence rate of the algorithm will be rapid, but the steady state mean square error (MSE) will increase. On the other hand, if the Step Size is small, the steady state MSE will be small, but the convergence rate will be slow. Many researches have been proposed to alleviate this drawback by using a variable Step Size. In this paper, a new variable Step Size LMS(VSSLMS) called Categorized VSSLMS (CVSSLMS) is proposed. CVSSLMS updates the Step Size by categorizing the current status of the gradient, hence significantly improves the convergence rate. The performance of the proposed algorithm was verified from the view point of convergence rate, Excessive Mean Square Error(EMSE), and complexity through experiments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.1
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• pp.95-100
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• 2020

This paper related with the performance evaluation of mSE-MMA (modified Signed Error-Multi Modulus Algorithm) adaptive equalization algorithm which is possible to reduce the distortion that is occurs in nonlinear communication channel like as additive noise, intersymbol interference and fading. The SE-MMA algorithm are emerged in order to reducing the computational load compared to the presently MMA algorithm, it has the degraded equalization performance by this. In order to improve the performance degradation of SE-MMA, the mSE-MMA controls the step size according to the existence of arbitrary radius circle of equalizer output is centered at transmitted symbol point. The performance of proposed mSE-MMA algorithm were compared to present SE-MMA using the same channel and noise environment by computer simulation. For this, the recoverd signal constellation which is the output of equalizer, residual isi and MD (Maximum Distortion), MSE learning curve which is represents the convergence performance and SER which is represents the roburstness of noise were used as performance index. As a result of simulation, the mSE-MMA has more superior to the SE-MMA in every performance index, and was confirmed that mSE-MMA has roburstness to the noise in the SER performance than SE-MMA especially.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.4
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• pp.280-287
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• 2008

For the reduction of common-mode noise level in Indirect-contact ECG (IDC-ECG) measurement a driven-right-leg grounding method was a lied to the IDC-ECG. Because the IDC-ECG does not require any direct contact between the electrodes and the human skin. it is adequate for un-constraining long-term ECG measurement at home and its various applications are now under development. However, larger 60 Hz noise induced by power line a ears in IDC-BCG than in conventional ECG, that is a restriction of IDC-ECG a application. In this study, the driven-right-leg ground which has been used in conventional direct-contact ECG, was adapted to the IDC-ECG measurement by feedback of the inversion of amplified common-mode noise to the body through the conductive fertile laid on the chair seat By this study, indirect-contact driven-right-leg ground was developed and it was shown to work stably. It was shown that the level of 60Hz power line noise was reduced to about -40 dB when the driven-right-leg gain was 1000. This study shows that we can extend the upper limit of the frequency band of IDC-ECG to 100Hz from 30Hz which is conventional upper limit in IDC-ECG, and we can raise the ground impedance between the body and conductive textile. So it is expected that the application area of the IDC-ECG will be extended by the results of this study.

• Microbiology and Biotechnology Letters
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• v.40 no.2
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• pp.83-91
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• 2012

Quorum sensing (QS) is a cell-to-cell communication system, which is used by many bacteria to regulate diverse gene expression in response to changes in population density. Bacteria recognize the differences in cell density by sensing the concentration of signal molecules such as N-acyl-homoserine lactones (AHL) and autoinducer-2 (AI-2). In particular, QS plays a key role in biofilm formation, which is a specific bacterial group behavior. Biofilms are dense aggregates of packed microbial communities that grow on surfaces, and are embedded in a self-produced matrix of extracellular polymeric substances (EPS). QS regulates biofilm dispersal as well as the production of EPS. In some bacteria, biofilm formations are regulated by c-di-GMP-mediated signaling as well as QS, thus the two signaling systems are mutually connected. Biofilms are one of the major virulence factors in pathogenic bacteria. In addition, they cause numerous problems in industrial fields, such as the biofouling of pipes, tanks and membrane bioreactors (MBR). Therefore, the interference of QS, referred to as quorum quenching (QQ) has received a great deal of attention. To inhibit biofilm formation, several strategies to disrupt bacterial QS have been reported, and many enzymes which can degrade or modify the signal molecule AHL have been studied. QQ enzymes, such as AHL-lactonase, AHL-acylase, and oxidoreductases may offer great potential for the effective control of biofilm formation and membrane biofouling in the future. This review describes the process of bacterial QS, biofilm formation, and the close relationship between them. Finally, QQ enzymes and their applications for the reduction of biofouling are also discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2C
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• pp.209-216
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• 2009

The repeater for wireless broadband internet (Wibro) system using OFDM demands the short processing delay to eliminate inter-symbol interference resulted from the time delay greater than the guard time. Towards this, the total system delay of repeater is expected to be minimized as possible as it can without distorting signal quality. In general, the FIR-type of filter is commonly deployed as a channelization filter, but due to its large amount of coefficients for producing prerequisite filter response the excessive large time delay occurs. To withstand this problem, the paper proposes the method for designing IIR filter whose response almost identical to that of the original filter. Moreover, in order to linearize the phase response of the designed IIR filter, this paper also introduce the way of designing the all-pass filter to be cascaded works for linearizing phase response of the channelization as well as the de-channelization filter. To achieve the further improvement in linearization of the phase response and reduction of the overall complexity, this paper tries to transform the integrated IIR filter group into the structure in polyphase style. The computer simulation verifies that the integrated IIR filter group designed in this paper reveals the relatively short processing delay without harming the acceptible signal quality.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.3
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• pp.27-34
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• 2024

The direct and indirect damages caused by fires in underground utility tunnels have a great impact on society as a whole, so efforts are needed to prevent and manage them in advance. To this end, research is ongoing to prevent disasters such as fire flooding by applying digital twin technology to underground utility tunnels. A network is required to transmit the sensed signals from each sensor to the platform. In essence, it is necessary to analyze the application of wireless networks in the underground utility tunnel environments because the tunnel lacks the reception range of external wireless communication systems. Within the underground utility tunnels, electromagnetic interference caused by transmission and distribution cables, and diffuse reflection of signals from internal structures, obstacles, and metallic pipes such as water pipes can cause distortion or size reduction of wireless signals. To ensure real-time connectivity for remote surveillance and monitoring tasks through sensing, it is necessary to measure and analyze the wireless coverage in underground utility tunnels. Therefore, in order to build a wireless network environment in the underground utility tunnels. this study minimized the shaded area and measured the actual cavity environment so that there is no problem in connecting to the wireless environment inside the underground utility tunnels. We analyzed the data transmission rate, signal strength, and signal-to-noise ratio for each section of the terrain of the underground utility tunnels. The obtained results provide an appropriate wireless planning approach for installing wireless networks in underground utility tunnels.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.17-22
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• 2007

OFDM (Orthogonal Frequency Division Multiplexing) is a special case of multicarrier transmission, where a single data stream is transmitted over a number of lower-rate subcarrier. One of the main reasons to use OFDM is to increase robustness against frequency-selective fading or narrowband interference. Unfortunately, an OFDM signal consists of a number of independently modulated subcarriers, which can give a large PAPR (Peak-to-Average Power Ratio) when added up coherently. In this paper, we investigate the performance of a simple PAPR reduction scheme, which requires no change of a receiver structure or no additional information transmission. The approach we employed is clipping in the time and frequency domains. The time-domain clipping is carried out with a predetermined clipping level while the frequency-domain clipping is done within EVM (Error Vector Magnitude). This approach is suboptimal with lower computational complexity compared to the optimal method. This evaluation is carried out on the OFDM system with an nonlinear amplifier. The simulation results demonstrated that the PAPR reduction algorithm is one of ways to reduce the effects of the nonlinear distortion of an HPA (High Power Amplifier).

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.684-690
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• 2010

Recently, the NG(Next Generation) system is studied for supporting convergence of various services and multi mode of single terminal. And a demand of user for taking the various services is getting increased, for supporting these services, many systems being able to transmit a large message have been appeared. In the NG system, it has to be supporting the CDMA and WCDMA besides the tele communication systems using OFDM method with single terminal An intergrated system can be improved with adopting of SoC technique. For adopting SoC technique on the intergrated terminal, we have to solve the non linear problem of HPA(High Power Amplifier). Nonlinear characteristic of HPA distorts both amplitude and phase of transmit signal, this distortion cause deep adjacent channel interference. We adopt a polynomial pre-distortion technique for this problem. In this paper, a noble modem design for NG mobile communication service and a method using polynomial pre-distorter with PAPR technique for counterbalancing nonlinear characteristic of the HPA are proposed.