• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.1
• /
• pp.1-9
• /
• 1994

In general, when IIR digital filter are designed from analog filters, the bilinera transformation and the impluse invariant tramsformation are commonly used. It is known, however, that high frequency response of digital filters designed by these transformations can not be well approximated to the sampled analog signals. In this paper, the symbol pulse invariant transformation is analyzed theoretically so that the symbol pulse invariant transformation which was originally application to a rectangular pulse is newly applied to double rate pulse signals and generic shape pulse signals. Also, the relation of spectra between a transfer function of digital filter and one of analog filter is considered. Further, we apply to design the digital high pass filters using the symbol pulse invariant transformation method.

• Journal of Communications and Networks
• /
• v.5 no.4
• /
• pp.365-373
• /
• 2003

This paper investigates the performance of M-ary pulse position modulation (PPM) multiuser ultra-wideband (UWB) communication systems in terms of symbol error rate (SER) over fading and additive white Gaussian noise (AWGN) channel. Based on Gaussian approximation for the multiple access interference, an expression for the signal-to-noise ratio (SNR) is derived for the UWB system. This expression is used to derive exact SER expressions for coherent UWB receivers. The effect of pulse selection on the SER of multiuser UWB system is studied. In addition to rectangular pulse, the 2nd derivative Gaussian waveform and Rayleigh pulses were considered. We show that the system capacity and/or SER performance can be significantly increased by using the monocycle pulse in fading channels.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.2
• /
• pp.389-396
• /
• 1988

Microprocessor-based software DDA interpolator is developed and applied to two axis contouring control of X-Y table. Developed assembly program is composed of feedrate, linear and circular DDA interpolation routines. Reference-pulse type of open-loop stepping motor control system in which the micro-computer produces a sequence of reference pulses for each axis of motion is adopted. To test performance of the developed program, X-Y table drive system based on stepping motor and shaft encoder is designed. Conturing error of the system in linear and circular path is within .+-. 0.2mm under start stop pulse rate of stepping motor.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.2
• /
• pp.139-147
• /
• 2003

In this paper we proposed system parameter values of M-ary PPM/TH(Pulse Position Modulation/Time Hopping) ultra-wideband systems having data rate of 100 Mbps for the frequency band, which is allocated by Federal Communications Commission(FCC). We also analyzed performance of the proposed system in the AWGN channels. According to the results of performance analysis, It is observed that available pulse duration is very limitative for this system. In case of constant data rate, if M and the pulse repetition numbers are increased, then the system performance is improved and the user number is decreased.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.63 no.7
• /
• pp.962-967
• /
• 2014

In this paper, through a digital potentiometer and exponentially weighted moving average filter, pulse and PPG waveform measurable device was fabricated in radial artery. If this device is not proper about signal size in analog part, MCU can judge easily by adjusted amplification through digital potentiometer, using exponentially weighted moving average filter is able to filter out more clear value of ADC. I presumed pulse rate as value of measuring time between point of maximum contraction from sensing signal in radial artery of wrist. Therefore, this means can measure stable pulse rate and PPG waveform, finger as well as radial artery, whether signal size of each person is different finger as well as radial artery.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.827-831
• /
• 1997

Conductive veramic matrix composite(CMC) workpiece of TiC 33%/Al /sab 2/O /sab 3/ 66% Y /sab 2/ O /sab 3/ was machined by die sinking electrical discharge machining(EDM) according to different pulse duration and suty factor for reverse polarity of electrode. Material removal rate(MRR) was examined by process under various operating conditions. The surface morphology was evaluated by surface roughness values and scanning electron microscopy(SEM) research. The more MRR was obtained according to increase pulse duration and duty factor. Also the maximum surface roughness(Rmax) of EDMed surface was slightly changed with increased pulse duration and duty factor. The SEM photographs of EDMed surface showed wide recast wide recast distribution region of melting materials in purse duration 0.130(ms) than 0.048(ms).

• Journal of Welding and Joining
• /
• v.15 no.6
• /
• pp.85-95
• /
• 1997

This study is to investigate the optimum conditions of Nd:YAG laser beam welding for Zircaloy-4 end cap closure by optical fiber transmission. Laser welding parameters which affect the penetration depth and bead width were experimentally examined using the various beam radius by the beam quality analyzer, joint geometries of end cap and the laser parameters which mean pulse width, repetition rate and pulse energy. Also, an optimum welding speed and the effect of assistant gas with varying the flow rate of He were investigated. We found that the laser average power for the end cap welding will be 230W and rotation speed must not exceed 8 RPM, the best position of focus using optical fiber with 600.mu.m will be 2 to 3mm below the surface of the material.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.6C
• /
• pp.569-574
• /
• 2006

We derive the general power spectral density of functions of ultra-wide bandwidth (UWB) systems using a pulse position modulation. We propose a new UWB system with a preferable line spectrum properies and a good bit error rate performance.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.55 no.12
• /
• pp.606-610
• /
• 2006

We investigated the output characteristics of Nd:YAG lasers at wavelength of 1444 nm, which were pumped by 450 Xe-flashlamp, 700 torr Xe-flashlamp and 700 torr Kr-flashlamp. With a Xe-flashlamp of 700 torr of gas pressure, the pulse energy of 0.738 J was obtained with repetition rate of 9.16 Hz and pumping pulse width of 400 ms. In case pumping pulse width of 5 ms and repetition rate of 1 Hz, 700 torr Kr-flashlamp showed the highest pulse energy of 1.44 J.

• Journal of Welding and Joining
• /
• v.22 no.1
• /
• pp.58-64
• /
• 2004

The control of the weld bead shape is important in laser welding of the small parts. The effects of laser welding parameters on the weld bead shape in the pulsed Nd:YAG laser welding of STS 304L material were investigated. Shielding gas type, flow rate, pumping voltage, pulse frequency, pulse width, focal position and overlap distance were selected as laser welding parameters. Experiments were designed and conducted using the Taguchi method which was a statistical experimental method. The weld bead width, penetration, area and aspect ratio were measured and analysed as the weld bead shape properties and the welding parameters were optimized to maximize the weld aspect ratio. Weld aspect ratio were greatly affected by the pulse width, pumping voltage and pulse frequency, and somewhat by the overlap distance, and little by the shielding gas type, flow rate and focal position. A confirmation experiment were conducted using the optimized welding parameters.