• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1024-1026
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• 2002

The active power filter(APF) is a good solution for elimination of harmonics, which is produced by the nonlinear loads such as static power converter, computer and so on. Our trademark of APF is a POSAPF-series, which was applied to Samsung Electronics corp, in January 2002, and which lines up from 50A to 500A. This equipment reduces total demanded distortion (TDD) by 2${\sim}$3%, which originally 11${\sim}$13%. This paper discusses the harmonic regulation, measurement and analysis, and describes control theories and design methods of POSAPF-series, and, finally, shows the experimental results of a real system.

• Journal of international Conference on Electrical Machines and Systems
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• v.3 no.2
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• pp.162-168
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• 2014

Use of nonlinear loads, such as power converters, fluorescent lamps and adjustable speed motor drives, is expected to grow rapidly. All of these loads inject harmonic currents. This paper presents the active filtering of the harmonic distortion generated by the compact fluorescent lamps (CFL). The Instantaneous active and reactive power theory (the p-q Theory) is used to design the control of parallel active filter. The control scheme has been verified using Matlab/Simulink with SimPower Systems through a set of simulation tests under different load conditions. Also, the tuning of the active power filter is performed to improve the quality of the electrical power supply.

• ETRI Journal
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• v.37 no.2
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• pp.338-347
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• 2015

The multi-carrier transmission signal in Multi-Carrier Code Division Multiple Access (MC-CDMA) has a high peak-to-average power ratio (PAPR), which results in nonlinear distortion and deteriorative system performance. An n-tuple selective mapping method is proposed to reduce the PAPR, in this paper. This method generates $2^n$ sequences of an original data sequence by adding n-tuple of n PAPR control bits to it followed by an interleaver and error-control code (ECC) to reduce its PAPR. The convolutional, Golay, and Hamming codes are used as ECCs in the proposed scheme. The proposed method uses different numbers of the n PAPR control bits to accomplish a noteworthy PAPR reduction and also avoids the need for a side-information transmission. The simulation results authenticate the effectiveness of the proposed method.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.245-248
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• 2000

In this paper, we present the performance of a multi-code parallel combinatory CDMA system using bi-orthogonal modulation under multipath fading channel. In general, the dynamic range of the amplitude of the transmit signal is very large in conventional multi-code CDMA systems, resulting in severe nonlinear distortion due to high power amplifier and thus significant BER performance degradation. Since the number of simultaneously multiplexed code channels in the proposed system is reduced, the proposed system exhibits reduction of peak-to-average power ratio (PAPR) of the transmit signal amplitude with significant BER improvement. We verify the performance of the proposed system by computer simulations under the Vehicular B multipath fading channel model by ARIB.

• Journal of IKEEE
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• v.15 no.1
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• pp.70-75
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• 2011

Longitudinal recording has been the cornerstone of all two generations of magnetic recording systems, FDD and HDD. In recent, perpendicular recording has received much attention as promising technology for future high-density recording system Research into signal processing techniques is paramount for the issued storage system and is indispensable like longitudinal recording systems. This paper focuses on the performance evaluation of the various detectors under perpendicular recording system. Parameters for improving the their performance are examined for some detectors. Detectors considered in this work are the partial response maximum likelihood (PRML), noise-predictive maximum likelihood (NPML), fixed delay tree search with decision feedback (FDTS/DF), dual decision feedback equalizer (DDFE) and multilevel decision feedback equalizer (MDFE). Their performances are analyzed in terms of mean squared error (MSE) and noise power spectra, and similarity between recording channel and partial response (PR) channel.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2E
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• pp.24-32
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• 1996

A rigorous theory for modeling, analysis, optimum nonseparable filter bank in multidimensional M-band quantized subband codec are developed in this paper. Each pdf-optimized quantizer is modeled by a nonlinear gain-plus-additive uncorrelated noise and embedded into the subband structure. We then decompose the analysis/synthesis filter banks into their polyphase components and shift the down-and up-samplers to the right and left of the analysis/synthesis polyphase matrices respectively. Focusing on the slow clock rate signal between the samplers, we derive the exact expression for the output mean square quantization error by using spatial-invariant analysis. We show that this error can be represented by two uncorrelated components : a distortion component due to the quantizer gain, and a random noise component due to fictitious uncorrelated noise at the uantizer. This mean square error is then minimized subject to perfect reconstruction (PR) constraints and the total bit allocation for the entire filter bank. The algorithm gives filter coefficients and subband bit allocations. Numerical design example for the optimum nonseparable orthonormal filter bank is given with a quincunx subsampling lattice.

• Journal of Power Electronics
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• v.17 no.2
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• pp.389-397
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• 2017

A control scheme for stand-alone inverters that utilizes an inductor current observer (ICO) is proposed. The proposed method measures disturbance load currents using a current sensor and it estimates the inductor current using the ICO. The filter parameter mismatch effect is analyzed to confirm the ICO's controllability. The ICO and controllers are designed in a continuous-time domain and transferred to a discrete-time domain with a digital delay. Experimental results demonstrate the effectiveness of the ICO using a 5-kVA single-phase stand-alone inverter prototype. The experimental results demonstrate that the observed current matches the actual current and that the proposed method can archive a less than 2.4% total harmonic distortion (THD) sinusoidal output waveform under nonlinear load conditions.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.951-954
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• 2000

In this paper, we present a multi-code parallel combinatory CDMA system using bi-orthogonal modulation to reduce envelope variation and improve bit error. .rate (BER) performance. In general, the dynamic range of the amplitude of the transmit signal is very large in the case of conventional multi-code CDMA systems, resulting in severe nonlinear distortion due to high power amplifier and thus significant BER performance degradation. The proposed system exhibits reduction of peak-to-average power ratio (PAPR) of the transmit signal amplitudes and significant performance improvement. We verify the performance of the proposed system by computer simulations under AWGN channel and flat fading channel.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.4
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• pp.505-513
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• 2006

A linear power amplifier is particularly emphasized on the system using a linear modulations, such as 16QAM and QPSK with pulse shaping. because intermodulation distortion which causes adjacent channel interference and co-channel interference is mostly generated in a nonlinear power amplifier. In this paper, parameters of a linearization loop, such as an amplitude imbalance a phase imbalance and a delay mismatch, are briefly analyzed to get a specific cancellation performance and linearization bandwidth. Experimental results are presented for IMT-2000 frequency band. The center frequency of the feedforward amplifier is 2140 MHz with 60 MHz bandwidth. When the average output power of feedforward amplifier is 20 Watt. the intermodulation cancellation performance is more than 21 dB. In this case, the output power of feedforward amplifier reduced 3.5 dB because of extra delay line loss and coupling loss. The feedforward amplifier efficiency is more than 7.2 % for multicarrier signals, 59 dBc for ACPR.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.69-74
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• 2005

The High Peak to Average Power Ratio (PAPR) could be a severe Problem in OFDM performance since it causes the significant distortion to the transmitting signal through a nonlinear device such as High Power Amplifier (HPA). In this paper, the performance of Peak cancellation method according to the HPA characteristic is comparatively analyzed with the clipping and windowing methods. The BER performances and the out-band power spectrums are demonstrated in detail.