• Progress in Medical Physics
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• v.13 no.2
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• pp.85-89
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• 2002

We authors developed a new small-size birdcage RF coil for animal MR images. And we compared signal-to-noise ratio (SNR) of the new small coil with a conventional knee coil. The dimension of the low-pass type birdcage coil with 12 elements at 37 MRI system are 13 cm outer diameter, 12 cm inner diameter and 20 cm length. For each element, the width of copper tape is 0.05 mm, thickness is 8 mm and length is 20 cm. The small birdcage coil with 12 elements exhibited 7 resonance modes. The isolation of the quadrature channel could be achieved more than 20 ㏈. The coil quality factor (Q value) was 98.6. The SNR of the animal coil was 243.2 on the average and was about twice as high as the conventional knee coil. The present study successfully demonstrated that the small birdcage coil could provide high quality animal MR images with the improved SNR. Therefore, it is expected that the small birdcage coil could be used in the clinical diagnosis and research studies for veterinary medicine in the near future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1015-1023
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• 1999

We propose nonlinear processing schemes for robust acquisition of direct-sequence spread spectrum (DS/SS) signals in wideband pulse jamming. To mitigate the interference effect due to impulse-like wideband jamming signals, the received signal is preprocessed by using the median filter, a simple order statistic filter Since only parts of the PN sequence are used for rapid acquisition, it is indispensable for analytic design of an acquisition scheme to have an appropriate model of the partial PN signal. The partial correlation of the median filtered PN signal is approximated by a two-piecewise linear model using an approximate upper bound. The acquisition performance of the proposed schemes is compared to that of other schemes. Finally, the analytic design is verified by computer simulation.

• Journal of the Korea Institute of Military Science and Technology
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• v.5 no.4
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• pp.38-48
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• 2002

Some signals, such as in radar system, are transmitted as periodic pulse trains. If more than one pulse train are transmitted over the same communication channel, a problem is to separate them for source identification and extract each pulse train at the receiver. This is known as pulse train deinterleaving. In this paper, we present an approach for deinterleaving the pulse trains and extracting their periods combining the estimation of the frequency of each pulse train by DFT, CDIF/SDIF histogram and Sequence Search technique. Also, we present the result of deinterleaving pulse trains and extracting PRI in the complex environment which multiple signals are interleaved.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.198-199
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• 2010

본 논문에서는 전기자동차의 구동에 핵심적인 역할을 하는 이차전지의 충전 방식 중 간단히 구현가능하며 성능이 뛰어난 정전류 정전압 알고리즘과 펄스 충전 알고리즘을 이론적으로 자세히 분석하였으며, 각각의 경우의 충전전류, 충전전압의 특성을 분석하였다. 또한 충전 시퀀스를 정리하였고 배터리 사고방지를 위한 $V_{th}$의 최대 설정치를 분석하였다.

• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.24-29
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• 2004

In ocean acoustic tomography (OAT), the pulse compression techniques using M-sequences are employed in the many studies for investigating the ocean structures. M-sequences can provide the good time and Doppler resolution in the process of demodulation using matched-filter. The signal-to-noise (SNR) performance at the output of receiver may be improved by manipulating received signal, i. e. coherently averaging. The processing time can be significantly reduced by using fast hadarmard transform (FHT) or fast Fourier transform (FFT). In this paper, we estimate the multipath arrival structures and delay times using the East Korean Sea experiment data and explore the compensation method for the detrimental effects on performance due to sampling rate error. We also analyze the characteristics of the ocean acoustic channels through scattering function, delay power profile, and time dispersions.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.6
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• pp.431-441
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• 2003

This paper presents the design of 32 bit microprocessor for a sequence control using a field programmable gate array(FPGA). The microprocessor was designed by a VHDL with top down method, the program memory was separated from the data memory for high speed execution of sequence instructions. Therefore it was possible that sequence instructions could be operated at the same time during the instruction fetch cycle. In order to reduce the instruction decoding time and the interface time of the data memory interface, an instruction code size was implemented by 32 bits. And the real time debug operation was implemented for easeful debugging the designed processor with a single step run, PC break point run, data memory break point run. Also in this designed microprocessor, pulse instructions, step controllers, master controllers, BM and BCD type arithmetic instructions, barrel shift instructions were implemented for sequence logic control. The FPGA was synthesized under a Xilinx's Foundation 4.2i Project Manager using a V600EHQ240 which contains 600,000 gates. Finally simulation and experiment were successfully performed respectively. For showing good performance, the designed microprocessor for the sequence logic control was compared with the H8S/2148 microprocessor which contained many bit instructions for sequence logic control. The designed processor for the sequence logic showed good performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.187-198
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• 2004

In this paper, we analyze the performance of BPM (Bi-Phase Modulation) UWB (Ultra Wide Band) multiple access system using PN (Pseudo Noise) code based time hopping sequence in indoor wireless channels. In particular, we compare BPM UWB multiple access system with PPM (Pulse Position Modulation) UWB multiple access system in terms of signalling and demodulation schemes. Moreover, we analytically evaluate the performance of these UWB systems by deriving the bit error rate expressions under the assumption that pulse energy and data transmission rate are identical for both systems. Simulation results in additive white Gaussian noise and realistic indoor multipath wireless channels show that the performance of BPM scheme is approximately 1 dB better than that of PPM scheme. However, the performance discrepancy becomes negligible as the number of users increases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.943-950
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• 2000

In this paper, an asynchronous multi-rate optical wireless pulse position modulation-code division multiple access (PPM-CDMA) is proposed for an indoor non-directed diffuse channel. As a signature sequence for CDMA, an optical orthogonal code (OOC) is used and an interference cancellation scheme is applied to improve the bit error rate. It is known that the optical PPM-CDMA has advantages due to its power efficiency. Moreover, it provides multi-rate services by varying the modulation level with fixed pulse duration. In the proposed multi-rate PPM-CDMA system with fixed pulse duration, chip rate and sampling time do not change for each transmission rate and this simplifies overall system structure.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.1
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• pp.144-152
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• 1996

In this paper, a pulse-mode digital multilayer neural network with a massively parallel yet compact and flexible network architecture is presented. Algebraicneural operations are replaced by stochastic processes using pseudo-random pulse sequences and simple logic gates are used as basic computing elements. The distributions of the results from the stochastic processes are approximated using the hypergeometric distribution. A statistical model of the noise(error) is developed to estimate the relative accuracy associated with stochastic computing in terms of mean and variance. Numerical character recognition problems are applied to the network to evaluate the network performance and to justify the validity of analytic results based on the developed statistical model. The network architectures are modeled in VHDL using the mixed descriptions of gate-level and register transfer level (RTL). Experiments show that the statistical model successfully predicts the accuracy of the operations performed in the network and that the character classification rate of the network is competitive to that of ordinary Back-Propagation networks.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.559-562
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• 2011

In this research, We derived Recursive Least Squares(RLS) algorithm with adaptive maximum-likelihood channel estimate for digital pulse amplitude modulated sequence in the presence of intersymbol interference and additive white Gaussian noise. RLS algorithms have better convergence characteristics than conventional algorithms, LMS (Least Mean Squares) algorithms.