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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of IKEEE
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Institude of Korean Electrical and Electronics Engineers
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Volume 2, Issue 2 - Dec 1998
Volume 2, Issue 1 - Aug 1998
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Speed Sensorless Control of Switched Reluctance Motor
Shin, Kyoo-Jae ; Kwon, Young-Ahn ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 166~172
Switched reluctance motor(SRM) has the advantages of simple structure, low rotor inertia and high efficiency. However, position sensor is essential in SRM in order to synchronize the phase excitation to the rotor Position. The Position sensors increase the cost of drive system and tend to reduce system reliability. This paper investigates the speed control of sensorless SRM in which the Phase current and change rate are utilized in position decision, and the period of dwell angle is variable for speed control. The proposed system consists of Position decision circuit, speed controller, digital logic commutator, switching angle controller and inverter The performances in the proposed system are verified through the experiment.
A study of optical wireless non-LOS link system
Kim, June-Hwan ; Hong, Kwon-Eui ; Kim, Yung-Kwon ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 173~177
Under indoor environment, in case that wireless optical LAN does not obtain the line-of-sight between transmitter and receiver, hemi-spherical lens or reflector must be adopted to get broader beam width. The beam tilt and the fluctuations in amplitude and phase of optical signal through indoor-space occur due to the turbulene. This fading often results in unacceptably large bit error probabilities and thus performance degradation of wireless optical communications. In this paper, when the spherical filter at the front-end of transmitter and receiver is used for wireless optical channel not satisfying line-of-sight, the signal-to-noise ratio as to zenithal angle and the effect from the turbulence due to indoor temperature are investigated.
Fabrication and Characteristics of Wavelength Insensitive Optical Fiber Coupler
Chang, Jin-Hyun ; Shin, Dong-Ho ; Jung, Jin-Ho ; Han, Wook ; Kim, Yung-Kwon ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 178~184
Optical fiber coupler is a crucial optical passive component for optical transmission systems. In this paper, we fabricate wavelength insensitive optical coupler(WIC), of two types for which the processing procedures are complicate and difficult. These couplers are fabricated by two optical fibers having either different fiber parameters or different cladding diameters. To clarify the validity, we measure the optical characteritics and compare to the data of theoretical simulation. The experiment results ref#eat that it has uniformity of about 1.0 dB and excess loss of less than 0.1 dB in the range of
Effective Fractal-Based Coding of Color Image Using YIQ Model
Kim, Seong-Jong ; Lee, Joon-Mo ; Shin, In-Chul ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 185~193
Fractal-based monochrome image coding method can be easily applied for color image compression by splitting the color image into different primary spectral channels such as RGB, YIQ or
, and encoding each channel independently According to this method, it needs to repeat the fractal coding for each channel, so it have the problem of encoding time. In this paper, a fractal-based coder for color still image is proposed which features the enhancement of compression rate and the reduction of coding time. As the result of the experiment where the proposed algorithm is applied far color images, the compression rate is enhanced by 28 : 1 above with average PSNR value
, do not lossless encoding process using JPEG. And the encoding time is reduced by maximum 11.5 %.
Repeaterless Transmission Length on the Atmospheric Wireless Optical LOS Communication Links
Jung, Jin-Ho ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 194~199
In the atmospheric wireless optical communication system, the low power transmission can be accomplished by the high directivity of laser beam. But, the transmitted optical signal undergoes the serious influences by the atmospheric effects like absorption, scattering, and turbulence because the transmission channel is the atmospheric space. In this paper, therefore, we obtain the link equation for an atmospheric wireless optical LOS communication link under the atmospheric effects and find the repeaterless transmission length to estimate the system performance through the computer simulation. From the results of the computer simulation, we present the transmission length that is possible to transmit without a repeater at given data rates and know that data rate is decreased rapidly when the transmission length is increased slightly at given bit error rate.
A Model and Design for DS/CDMA System with Base-received Power Control and Pilot Power Control
Lim, Kwang-Jae ; Kim, Baek-Hyun ; Kwak, Kyung-Sup ; Park, Pan-Gyong ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 200~211
A DS/CDMA system that makes all base stations require equal received power for all mobiles can lead to the non-uniform quality of service when mobiles are non-uniformly located over a service area. In order to resolve this problem the base-received power should be controlled according to base's load in order to make the quality of service uniform, and the pilot power also has to be adjusted to maintain the balance of cell coverage between reverse link and forward link. In this paper, we propose a generalized model including Pilot Power control, base-received power control on the reverse link, transmission power allocation on multiple forward link, and soft handoff on both links. We also apply our model to an initial system design as an example.
A Demodulation Method for DS/CDMA Systems
Jung, Bum-Jin ; Jin, Ming-Lu ; Kwak, Kyung-Sup ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 212~224
There are two major factors of degrading the performance in the forward link of DS/CDMA systems. One is the multiple access interference (MAI) caused by using the same frequency bands simultaneously and the other is the multipath lading due to multipath propagation. PN codes which have minimum cross correlation properties among spread spectrum codes are necessary to reduce the MAI. In the conventional IS-95A system, the PN sequence has the period of
and is of the length of 64 chips for spreading each data. In this case, since the length of PN code per bit is very short compared to the period of the PN code, the performance of the conventional system is not satisfied in view of suppressing the multipath interference. However, the correlation property of the PN codes at the demodulation can be improved by increasing the interval of Integration at the demodulation. This paper proposes a demodulation method to reduce the cross correlation among PN codes. The performance of the proposed demodulation method is investigated through computer simulations. We used multipath Ray lading channel and AWGN channel in the simulation. Our simulation results show the improved performance of
SNR in a given BER compared to the conventional demodulation scheme.
A study of the Implementation of Adaptive De-interlacing Algorithm with Improved Horizontal and Vertical Edges
Kwon, Yong-Jae ; Park, No-Kyung ; Moon, Dai-Tchul ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 225~232
Currently NTSC, PAL, and SECOM are widely used for TV broadcasting systems. In Korea, NTSC has been used to reduce transmission bandwidth and broadband flickers using the Interlaced scanning method. Image data in the Interlaced scanning method require De-interlacing compensation for PC-based multimedia applications. The existing compensation algorithms such as ZOI, FOI, and ELA provieds simple computations and effective image compensation while the PSNR is low and horizontal and vertical edges are hardly detected. In this paper, the ADI(Adaptive De-Interlacing) algorithm that can increase PSNR and detect horizontal and vertical edges is proposed and a hardware system is implemented using three ACTEL 1020B FPGA chips. The system consists of the algorithm part implemented using two FPGAs and the memory control part implemented using rest one. Also the system operation is investigated for real time processing.
Implementation of G.726 ADPCM Dual Rate Speech Codec of 16Kbps and 40Kbps
Kim Jae-Oh ; Han Kyong-Ho ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 233~238
In this paper, the implementation of dual rate ADPCM using G.726 16Kbps and 40Kbps speech codec algorithm is handled. For small signals, the low rate 16Kbps coding algorithm shows almost the same SNR as the high rate 40Kbps coding algorithm , while the high rate 40Kbps coding algorithm shows the higher SNR than the low rate 16Kbps coding algorithm fur large signal. To obtain the good trade-off between the data rate and synthesized speech quality, we applied low rate 16Kbps for the small signal and high rate 40Kbps for the large signal. Various threshold values determining the rate are applied for good trade-off between data rate and speech quality. The simulation result shows the good speech quality at a low rate comparing with 16Kbps & 40Kbps.
Efficiency Improvement of Morphological Details Extraction using Post-it Transformation for Very Low Bit-Rate Video Compression
Huh, Si-Heng ; Eo, Jin-Woo ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 239~246
In this paper, a new morphological details extraction algorithm is proposed. It is known that separate transmission of details and background smoothed image is a powerful technique for very low bit-rate video data transmission. Several details extraction algorithms show relatively large variation of grayscale levels in details, smoothed image, which is the difference between original and details images, provides highly distortedand complicated result. In order to remedy those pitfails, and thus to improve the coding efficiency, we propose a new algorithm using the reconstruction top-hat result as the reference image in process of obtaining details, instead of top-hat result, which is used fur existing a1gorithms. Experimental results show that details, extracted using the proposed algorithm, are much similar to original image, and thus the smoothed image is not too complicated.
Performance Comparison of Two Parallel LU Decomposition Algorithms on MasPar Machines
Kim, Yong-Tae ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 247~254
This paper presents a performance study of two LU decomposition algorithms on two massively parallel SIMD machines: the 16K processor MasPar MP-1 and the 4K processor MasPar MP-2. The paper presents experimental results and an analysis of the algorithms to explain the results. While the blocked and the nonblocked algorithms for LU decomposition have been studied individually by others, we compare the two algorithms and identify the tradeoffs between them. Our analysis of the blocked algorithm shows how the block size affects the interprocessor communication cost and the memory read/write overhead. The analysis in this paper is useful to determine an optimum block size for the blocked algorithm.
The MPPT of Photovoltaic Solar System by Controlled Boost Converter with Neural Network
Cha, In-Su ; Lim, Jung-Yeol ; Yu, Gwon-Jong ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 255~262
The neural network can roughly be classified as the specialized control, indirect control and general schemes. Neural network is adopted for MPPT of solar array. And back propagation algorithm also is used to train neural network controller. We investigate the possibilities of
control using the neural networks, and then we also examine about operating the solar cell at an optimal voltage comprise of temperature compensated voltage with boost converter. Proposed boost converter of MPPT system is studied by simulation and is implemented by using a microprocessor(80c196kc) which controls duty ratio of the boost converter.
PID Autotuning Algorithm Based on Saturation Function Feedback
Oh, Seung-Rohk ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 263~269
We use the slope bounded saturation nonlinear feedback element instead of relay to find ultimate gain and period of linear plant. Saturation nonlinear element reduces the high harmonics of plant output. The reduction of high harmonics improve the accuracy of describing function method used to find ultimate gain and period. We give a simple procedure to find ultimate gain and period with saturation nonlinear element. A PID controller design method with known time delay element is also given, which is very useful when oscillation is not occurred with nonlinear element.
A Study on the Analysis of Performance for a Real-time Distributed Control System with Reliability
Kim, Nae-Jin ; Park, In-Kap ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 270~277
As the network technologies advance, the control systems progress from a centralized architecture to a distributed one. However, these control systems were designed mostly based on the general-purpose operating systems(OS) and have many problems for assurance of a real-time property required for plant processing fields. Therefore, the control systems far a plant process upon real-time OS hare been increased gradually. In this paper, the real-time OS emphasizes on the realization of real-time processing capability, reliability of real-time response, and multi-processing functionality which are prerequisites for a distributed control system. And on the basis of this OS, the number of executable loop and logic, the functions of main plant processing, was analyzed and its validity was also evaluated. The system in this paper was designed not to effect on processing data while online, and the time spent on switching was measured.
A3V 10b 33 MHz Low Power CMOS A/D Converter for HDTV Applications
Lee, Kang-Jin ; Lee, Seung-Hoon ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 278~284
This paper describes a l0b CMOS A/D converter (ADC) for HDTV applications. The proposed ADC adopts a typical multi-step pipelined architecture. The proposed circuit design techniques are as fo1lows: A selective channel-length adjustment technique for a bias circuit minimizes the mismatch of the bias current due to the short channel effect by supply voltage variations. A power reduction technique for a high-speed two-stage operational amplifier decreases the power consumption of amplifiers with wide bandwidths by turning on and off bias currents in the suggested sequence. A typical capacitor scaling technique optimizes the chip area and power dissipation of the ADC. The proposed ADC is designed and fabricated in s 0.8 um double-poly double-metal n-well CMOS technology. The measured differential and integral nonlinearities of the prototype ADC show less than
, respectively. The typical ADC power consumption is 119 mW at 3 V with a 40 MHz sampling rate, and 320 mW at 5 V with a 50 MHz sampling rate.
Unequal Error Protection and Error Concealment Schemes for the Transmission of H.263 Video over Mobile Channels
Hong, Won-Gi ; Ko, Sung-Jea ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 285~293
This paper presents unequal error protection and error concealment techniques far robust H.263 video transmission over mobile channels. The proposed error protection scheme has three major features. First, it has the capability of preventing the loss of synchronization information in H.263 video stream as much as possible that the H.263 decoder can resynchronize at the next decoding point, if errors are occurred. Secondly, it employs an unequal error protection scheme to support variable coding rates using rate compatible punctured convolutional (RCPC) codes, dividing the encoded stream into two classes. Finally, a macroblock-interleaving scheme is employed in order to minimize the corruption of consecutive macroblocks due to burst errors, which can make a proper condition for error concealment. In addition, to minimize the spatial error propagations due to the variable length codes, a fast resynchronization scheme at the group of block layer is developed for recovering subsequent error-free macroblocks following the damaged macroblock. futhermore, error concealment techniques based on both side match criterion and overlapped block motion compensation (OBMC) are employed at the source decoder so that it can not only recover the lost macroblock more accurately, but also reduce blocking artifacts. Experimental results show that the proposed scheme can be an effective error protection scheme since proper video quality can be maintained under various channel bit error rates.
Running Inverse for Implementing Decorrelating Detectors in Synchronous DS/CDMA Systems
Joo, Jung-Suk ; Lee, Yong-Hoon ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 294~298
We propose an efficient method for updating the inverse of the signature waveform cross-correlations (SWC) matrix when the number of users in the synchronous direct-sequence code-division multiple-access (DS/CDMA) system changes. It is shown that the computational complexity of the proposed method is
in which n represents the number of active users in the system.
Speed Control of SRM by Pl Controller with Fuzzy Logic Modifier
Kim, Bo-Hyung ; Kim, Jae-Mun ; Won, Chung-Yuen ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 299~308
In this paper, reliable switched reluctance motor(SRM) drive system and 4-rule based fuzzy logic modifier(FLM) of the conventional PI controller are presented. The i80C196KC, low-cost one-chip microcontroller is used for designing SRM drive controller which include the speed controller and the starting sequence. The fuzzy logic modifier which exhibits a stabilizing effects on the closed-loop system, has good robustness regarding the improperly tuned PI controller. The simulation and experimental results are performed to verify the capability of proposed control method on 6/4 salient type SRM.
An 8b 52 MHz CMOS Subranging A/D Converter Design for ISDN Applications
Hwang, Sung-Wook ; Lee, Seung-Hoon ;
Journal of IKEEE, volume 2, issue 2, 1998, Pages 309~315
This paper describes an 8b 52 MHz CMOS subranging analog-to-digital converter (ADC) for Integrated Services Digital Network (ISDN) applications. The proposed ADC based on the improved time-interleaved architecture removes the holding time which is typically observed in the conventional double-channel subranging ADCs to increase throughput rate. Moreover, the ADC employs the interpolation technique in the back-end subranging ADCs far residue signal processing to minimize die area and power consumption. The fabricated and measured prototype ADC in a 0.8 um n-well double-poly double-metal CMOS process typically shows a 52 MHz sampling rate at a 5 V supply voltage with 230 mW, and a 40 MHz sampling rate at a 3 V power supply with 60 mW power consumption.