• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1552-1557
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• 2015

The paper unleashes a new idea to arrive at reduced switch count topological structures configured in the form of a matrix for a cascaded Multi level inverter (CMLI). The theory encircles to minimize the number of switches involved in the conduction path and there from acclaim reduced input current distortion, lower switching losses and electromagnetic interference. The focus extends to standardize the number of power devices required for reaching different levels of output voltage from the same architecture. It includes appropriate pulse width modulation (PWM) strategy to generate firing pulses and ensure the desired operation of the power modules. The investigative study carries with it MATLAB based simulation and experimental results obtained using suitable prototypes to illustrate the viability of the proposed concept. The promising nature of the performance projects a new dimension in the use of single phase MLIs for renewable energy related applications.

• The Magazine of the IEIE
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• v.30 no.3
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• pp.295-295
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• 2003

The advantages of using analogue optical networks for delivering radio signals from a central location to many remote antenna sites have been recognized. In a telecommnications context, radio signals may be for fixed radio access, cordless or mobile networks, but the same principles apply. By making use of the high bandwidth, low loss characteristics of optical fiber, all high frequency and signal processing functions can be performed centrally and signals can then be transported over the optical network directly at the carrier frequency. The remote sites then become very simple, requiring only optoelectronic conversion, filtering and linear amplification. This shifting of the complex functionality away from the remote site allow cheap, reliable, small and light-weight radio access points with low power consumption to be deployed. In this paper, we show that an electroabsorption modulation(EAM) may be used as a single component in such a radio access point, as a passive transceiver for small-sized cell(picocells).

• The Magazine of the IEIE
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• v.30 no.3
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• pp.81-85
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• 2003

The advantages of using analogue optical networks for delivering radio signals from a central location to many remote antenna sites have been recognized. In a telecommnications context, radio signals may be for fixed radio access, cordless or mobile networks, but the same principles apply. By making use of the high bandwidth, low loss characteristics of optical fiber, all high frequency and signal processing functions can be performed centrally and signals can then be transported over the optical network directly at the carrier frequency. The remote sites then become very simple, requiring only optoelectronic conversion, filtering and linear amplification. This shifting of the complex functionality away from the remote site allow cheap, reliable, small and light-weight radio access points with low power consumption to be deployed. In this paper, we show that an electroabsorption modulation(EAM) may be used as a single component in such a radio access point, as a passive transceiver for small-sized cell(picocells).

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.1-13
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• 1995

In this paper, a specification for wireless LAN MODEM using direct sequence spread spectrum (DS/SS) technique is presented. Some algorithms and hardware architectures for an efficient implementation of the DS/SS MODEM are suggested. In the method, all baseband signal processing are done digitally for single chip implementation. Schemes of DQPSK baseband modulation/demodulation, despreading with digital matched filter, digital timing recovery, and efficient carrier sensing are among the discussed algorithms. We also performed various kinds of simulations to evaluate the system performance and to extract parameters for hardware implementation. In addition, the pictorial view of ASIC of the SS MODEM is also shown.

• Journal of IKEEE
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• v.19 no.1
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• pp.27-32
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• 2015

A flexible and tunable microwave photonic filter based on adjustable optical frequency comb source is demonstrated. We use a combination of a dual parallel Mach Zehnder modulator and an intensity modulator to generate fifteen comb lines with proper weights to implement a desired filter. The optical comb weights, corresponding to the tap coefficients of the filter, are flexibly changed by adjusting the operation parameters of the modulators. The achieved bandwidth and stopband attenuation of the tunable filter are 0.7 GHz and 20 dB, respectively. In addition, we overcome the undesired low frequency suppression appeared in a conventional scheme by applying a dual parallel Mach Zehnder modulator for single sideband suppressed carrier modulation.

• The Journal of the Acoustical Society of Korea
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• v.34 no.2
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• pp.91-97
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• 2015

In this paper, wireless communication from a smart phone to a hearing aid using audible frequency band sound was considered. 1kHz single channel carrier frequency was applied for amplitude shift keying (ASK) binary data modulation, and the result of the transmission and reception was tested. The overall system process was precisely explained and experimentally evaluated. The result will be applied for realizing a digital hearing aid with remote control feature by a smart phone.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2003.06a
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• pp.217-221
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• 2003

In this paper, the Viterbi decoder containing new branch metrics of the squared Euclidean distance with multiple order phase differences is introduced in order to improve the bit error rate (BER) in the differential detection of the trellis-coded MDPSK-OFDM. The proposed Viterbi decoder is conceptually same as the multiple Phase differential detection method that uses the branch metric with multiple phase differences. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbi decoder improves BER performance without sacrificing bandwidth and power efficiency. Also, the proposed algorithm can be used in the single carrier modulation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.250-257
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• 2004

MC-CDMA and OFDM are digital modulation techniques where a single data symbol is transmitted at multiple subcarriers which we orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of multi currier systems is analyzed. when data is transmitted over multi-path Rayleigh fading channel. The performance of this technique, gauged by the average bit error rate, is numerically analyzed for the system with the application of antenna diversity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.4
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• pp.369-376
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• 2016

In this paper, we propose and design a SSD(Simultaneous Single band Duplex) system using 5G(Generation) candidate modulations. Especially, we consider HPA(High Power Amplifier) nonlinearity in the proposed system. And then, we evaluate and analyze performance of the proposed system. As simulation results, performance of SSD-OFDM(Orthogonal Frequency Division Multiplexing), SSD-FMC (Universal Filtered Multi-Carrier), and SSD-FBMC(Filter Bank Multi-Carrier) is severely degraded by HPA nonlinearity. However, performance of SSD-OFDM, SSD-UFMC, and SSD-FBMC is similar in the same condition. That is, OFDM, UFMC, and FBMC have a similar PAPR(Peak to Average Power Ratio) characteristic. Finally, we can confirm that the proposed SSD system can not cancel(SI) self-interference effectively by strong HPA nonlinearity. That is, Reducing PAPR is important in order to avoid effect of HPA nonlinearity in the proposed SSD system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.245-249
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• 2004

In this paper, we have proposed a clock recovery algorithm of Orthogonal Frequency Division Multiplexing/Quadrature Phase Shift Keying Modulation-Digital Microwave Radio(OFDM/QPSK-DMR) system using Band Limited-Pulse Shaping Filter(BL-PSF) and compared the clock phase error variance of OFDM/QPSK-DMR system with that of single carrier DMR system. The OFDM/QPSK-DMR system using windowing method requires training sequence or Cyclic Prefix (CP) to synchronize the clock phase of received signal. But transmit efficient is increased in our proposed DMR system because of no using redundant data such as training sequence or CP. The proposed clock recovery algorithm is simply realized in the OFDM/QPSK-DMR system using BL-PSF. The simulation results confirm that the proposed clock recovery algorithm has the same clock phase error variance performance in a single carrier DR system under Additive White Gaussian Noise(AWGN) environment.