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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Journal of Korean Institute of Electromagnetic Engineering and Science
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Journal DOI :
The Korean Institute of Electromagnetic Engineering and Science
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Volume & Issues
Volume 9, Issue 6 - Dec 1998
Volume 9, Issue 5 - Oct 1998
Volume 9, Issue 4 - Aug 1998
Volume 9, Issue 3 - Jun 1998
Volume 9, Issue 2 - Apr 1998
Volume 9, Issue 1 - Feb 1998
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Error Performance Analysis of Trellis Coded QPSK Signal with Reed-Solomon Coding and MRC Diversity Reception in Micro-Cellular System
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 427~438
The bit error rate(BER) performance of Trellis Coded QPSK signal in the presence of cochannel interference (CCI) and Rician fading is investigated. The trellis coded QPSK system adopts Maximum Ratio Combining (MRC) diversity reception and Reed-Solomon code to enhance system performance. Using the derived error probability equation, the error performance of trellis coded QPSK system has been evaluated and shown in figures to discuss as a function of signal power to noise power ratio (SNR), signal power to interference power ratio(SIR), direct to indirect signal power ratio (
), the number of diversity branch (M), the frame length of Reed-Solomon code (n), the number of error correction symbol (t), and the number of state of trellis encoder. From the results, we know that proposed system is affected by cochannel interference and fading in microcell environment. Also, BER performance of Trellis Coded QPSK system can be improved as increasing either the power of desired signal or the value of SIR. And the BER floor in microcellular system is caused by the cochannel interference and it occurs at high BER when SIR is low. And Reed-Solomon code (n=15, t=2) is more effective to restrain the affection of CCI and fading than MRC diversity reception (M=2)
Performance Analysis of DS-CDMA Communication Systems with Array Antenna and CCI Canceller
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 439~449
In this paper, error performance of DS-CDMA communication system has been analyzed in a radio channel which is characterized by multi-user interference (MUI). Also, performance improvement has been obtained by both numerical analysis and simulation techniques when 3-element array antenna and co-channel interference (CCI) canceller are employed as a means for overcoming an MUI effect. The MUI was modelled as a gaussian random process. In array antenna scheme we only considered a directivity of antennal. The results show that there is a substantial enhancement in performance by employing an array antenna or a CCI canceller. CCI canceller gives better improvement in performance than the array antenna with D=2.67. Additional improvement can be obtained when the array antenna and the CCI canceller are adopted in cascade form. In this case the error performance approaches that of AWGN environment.
An Analysis of the Spatial Distribution of Multipath Fading using Miniaturized Experimental Setup
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 450~461
The spatial distribution of multipath fading using miniaturized experimental setup was analyzed. The spatial Fourier transform was carried out for the analysis of the period of fading and we could find out spatial frequency component of fading. Thus the analysis using this method shows the validity of miniaturized experimental setup. The miniaturized experimental setup was made by 5 times reducing of the real size. The simulation was performed at 2 GHz and the measurement was carried out at 10 GHz. Automatic antenna moving system was made for exact measurement of the multipath fading. Both simulated and measured results in miniaturized experimental setup were shown by electric field distribution and spatial frequency density distribution curves.
Outage Probability Analysis for Mobile Radio System Added Background Noise in Urban Area
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 462~472
In this paper, considering the Rayleigh fading, the lognormal shadowing, and the man-made noise which is occurred in urban area randomly, the mobile radio channel and the radio propagations are analyzed. The system affected by the noise is compared to other modelings. The fading, shadowing, and background noise are wholly considered to evaluate the mobile radio propagation effectively. For N=0.000001, the outage probability in the absence of noise is
, in the fading only
, and in the presence of noise
. The analysis with the presence of noise is very important for the performance evaluation of mobile radio system
Design of the Electromagnetic Coupling Wideband Microstrip Antenna using FDTD Method
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 473~482
In this paper, characteristics of the wide band microstrip antennas with parasistic element are analyzed by the Finite Difference Time Domain(FDTD) method, and antenna parameters are optimized to get maximum bandwidth, retern loss, input impedance, and radiation pattern are calculated by Founier transforming the time domain results. The characteristics of the antenna are varied and the bandwidth of the antenna is broaded as a length and a width of the driven element, a gap of the driven element and the parasitic element, a width and a length of parasitic element. So the different patchs are resonating at different frequencies and this multipule resonance increase the bandwidth. The Results of the calculation and measurement, the size of the antenna with parasitic element is about a twice larger than a microstrip antenna, but bandwidth is four times better than a microstrip antenna. And these results were in relatively good accordance with the measured values.
FDTD Analysis of the Absorption Characteristics for Grid Ferrite Electromagnetic Wave Absorber
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 483~490
The reflectivity of a grid ferrite electromagnetic wave absorber is analyzed using finite difference time domain (FDTD) method, which is usually used in anechoic chambers for EMI / EMS test. The frequency dispersive characteristics of ferrite medium and its boundary condition are modeled using magnetic flux in addition to E- and H-fields. By applying Floquets theorem, FDTD analysis of the grid ferrite absorber with periodic infinite array is simplified as a unit cell problem. The method of homogenization which is mainly utilized in the calculation of absorber reflectivity as a low frequency technique takes only into account volume fraction of the unit cell of the absorber except for the structure of medium geometry. However, the presented method in this paper can analyze the geometry effect of the unit cell with its medium characteristics up to high frequency region.
Computation of Absorbed Power adiated from a Portable Phone Using FDTD
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 491~498
Based on FDTD(Finite-Difference Time-Domain) method the human head absorbed power radiated from a 1.8 GHz portable phone is computed. For this computation the 7 layered media for the human head modeling and the monopole antenna attached to metallic box for the portable phone are used. To reflect the real circumstances typical sizes of human heads and portable phones are considered in the calculation. The length of monopole antenna is 4.5 cm. Under the predetermined model the distribution of SAR over the human head are calculated, and from which the place of maximum SAR is near the head skin surface, not deep places far into the head. The computation shows the maximum SAR to be 1.4 mWg somewhat less than the internationally adopted value of 1.6 mW/g.
Estimation of Discharge Current Waveshapes in Short Gap Discharge by One Antennal Method
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 499~505
This paper presents the method for an estimation of discharge current waveshapes in short gap discharge by a radiated electromagnetic field. The method of currentwaveform estimation described is using the one antenna method(single field method) with a measured electric or magnetic fields at given field point by a time domain antenna. In order to verify the availability of the estimated theory, the discharge current waveshape estimation was performed by one antenna method using the measured electric fields of Wilson & Ma and compared with experiments.
The Design and Fabrication of X-Band MMIC Low Noise Amplifier for Active antennal using P-HEMT
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 506~514
The design and fabrication of X-band(11.7~12 GHz) 2-stage monolithic microwave integrated circuit(MMIC) low noise amplifier (LNA) for active antenna are presented using
AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (P-HEMT). In each stage of the LNA, a series feedback by using a source inductor is used for both input matching and good stability. The measurement results are achieved as an input return loss under -17 dB, an output return loss under -15dB, a noise figure of 1.3dB, and a gain of 17 dB at X-band. This results almost concur with a design results except noise figure(NF). The chip size of the MMIC LNA is
A Study of Dual-Frequency Microstrip Patch Antenna
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 515~525
In this paper, for both transmission and reception with single antenna system of satellite communication, dual-frequency antennas which operate simultaneously at 12.5 GHz and at 14.25 GHz are designed, constructed and measured. Also by using dual feeding structure, the problems of single-fed dual-frequency antenna such as the separation of transmitting and receiving signals and single polarization, are solved. Microstrip patch as a radiation element of dual-fed dual-frequency antenna has width and length which are the resonance lengths of the corresponding frequencies for transmission and reception, respectively. The effects of the feed line on the other frequency feeding are minimized with the optimal matching scheme for the feed lines. For solving the space problems of dual-fed two-dimensional array antennas, microstrip-line and coaxial probe feedings are used for each frequency and a two-dimensional
array antenna was designed and measured their characteristics. The experimental results show that errors of resonance frequencies are less than 1.44%, the return losses are less than -21 dB and the isolations between two feeding ports are less than -21 dB. The characteristics of radiation patterns of dual frequency microstrip antenna are measured and evaluated. The directivities, sidelobe levels and cross polarizations are also measured and compared with the simulations. The results show some errors due to the misalignment of coaxial probe feeding.
Analysis of Cellular Phone대s Far-Field Pattern and Near-Field Using TLM Method
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 526~534
The electric near-fields from a cellular phone's antenna are calculated using TLM method. The cellular phones is assumed to be a conductive box and the frequency is set to be 900 [MHz] and the radiated power is set to be 0.6 [W]. The near-fields and far-field patterns are obtained for wire antennas of 1/4 and 1/2 wavelengths. For the same radiation power, (0.6 [W]), it is found out the near-field for antennal length of λ/2 is much weaker than that for λ/4 antenna. The maximum SAR calculated in a simple head model becomes 1.4[W/kg].
A Small Cavity Bandpass Filter using Triple-Mode Technique
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 535~541
A 2 stage 6-pole bandpass filter(BPF) is designed and implemented by using triple-mode cavity for satellite payload system. The BPF has an 100 MHz bandwidth at the center frequency of 14.5 GHz, Ku-band. The cavity filter uses two orthogonal
modes and one
mode. The intercavity coupling between the adjacent cavities results in a Chebyshev response and is accomplished by H-field component of TE modes. The size and location of intercavity slot are determined by the coupling equation from H-field of TE resonant modes in circular cavity. The measured filter response agrees well with the theoretical data.
A Study on Error Compensation for Quadrature Modulator in Frequency Direct Conversion Method
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 542~551
In this study, a method of error compensation for channel gain imbalance, phase imbalance and local oscillator leakage in the modulator of frequency direct conversion is suggested. The compensation of channel imbalance can be carried out by using the received power after transmitting test signal. By applying this method, the phase imbalance conversion with frequency can be easily compensated since this method is rarely affected by the transmission channel. It is confirmed that the algorithm proposed in this study(iteration coefficient=11) converges faster than conventional algorithm(iteration coefficient=43). From the numerical results, the DC-offset, channel gain, phase imbalance compensation coefficient and iteration number converges into(
=-0.0524, N=13) when the local oscillator leakage is not considered. However, it converges into(
=-0.0524, N=16) when the local oscillator leakage is considered.
A Study on the Design of Conducted Noise Separator for Power Line Noise
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 4, 1998, Pages 552~559
Conducted noise in power line contains both the common mode(CM) and differential mode(DM) noise. These two modes of noise are caused by different noise sources and paths. Therefore, CM/DM noise must be deal with individually in EMI filter. In this paper the technique to separate power line noise is presented, which can be used to measure both the CM and the DM noise from total generated noise. Also, noise-separator is designed and experimental results showed 30 dB above of separation performance in 10 kHz~10 MHz.