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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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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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A Study on Adaptive Linear MMSE Detector for DS-CDMA Reverse Link in Rayleigh Fading Environment
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 131~140
MAI(Multi-Access Interference) and fast channel variation due to the fading environment are the major problems in the mobile CDMA communication systems. Recently, interest has been increasing in applying the Adaptive Linear MMSE Detector to MAI cancellation in the CDMA reverse link. In this paper, we propose a modified Adaptive Linear MMSE Detector structure which can be used in Long-duration code CDMA system in the presence of independent Rayleigh fading. We use independent multiple tap-weight vector structure to cope with the variation of spreading sequence pattern between neighbor symbols because of the Long-duration code. In this case, more exact channel parameter estimation is required. To solve this problem, we use coherent CDMA structure which can track the channel parameters like amplitude and phase by employing the low power pilot channel in the CDMA reverse link.
Modified Transmission Line Type Antennal for the Beam Tilt
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 141~148
For developing a beam shaping antenna, the circumference and the length of the vertical and horizontal elements of the Modified Transmission Line type Antenna(MTLA) are varied. The vertical radiation pattern of MTLA which has various shape was analyzed by the moment method in order to verify the beam tilt characteristics. From the analysis, it is confirmed that the condition of the maximum beam tilt is determined by the length of the vertical elements of the antenna. The antennal with the maximum beam tilt was designed and its input impedance and the radiation pattern was calculated theoretically and measured experimentally.
Comparison with SAR Patterns of Biological Objects Contacted with Coaxial Waveguide Antenna Using MUR and GPML ABCs in the FDTD Method
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 149~158
The SAR patterns of biological objects contacted with coaxial waveguide antennal has been investigated, in which the biological object was modeled by a homogeneous and four-layered lossy human body. We derived the finite-difference time-domain(FDTD) algorithm and equation of MUR and generalized perfectly matched layer(GPML) ABCs in cylindrical coordination. The coupling between coaxial waveguide antenna and a biological object was analyzed by use of MUR and GPML ABCs in the FDTD method to obtain the absorbed power patterns in the media. The specific absorption rates (SAR) distribution which was corresponding to the temperature distribution was calculated in each region by use of the steady-state response in the FDTD method. The SAR patterns of the FDTD method using MUR absorbing boundary conditions(ABCs) was compared with those of the FDTD method using GPML ABCs. The comparison exhibits that the penetration depth of the SAR patterns using MUR ABCs is deeper than that of the SAR patterns using GPML ABCs because of loss in free space. However, the spread in the lateral directions of the SAR patterns using GPML ABCs is smaller than of the SAR patterns using MUR ABCs.
Measurements and Statistical Modeling of Man-made Noise
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 159~170
Man-made noise in PCS frequency range are measured using the three axis antennal with common port and the measured data are statistically treated for modeling. The can optimal parameters of the measured APD curves can be calculated fast by using the Composite Approximation Algorithm. The calculated APD parameters can reduce the EM-environments Data Base memory and also be applied to determine the output and sensitivity margin of the transmitter and the receiver.
A Study on the Design of Microwave Oscillator Output Matching Circuit Using 3-dB Coupler Tuner
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 171~178
Generally, the output matching circuit has the most influence to the output power of oscillator and existing method for output matching has difficulty for making the optimum output matching circuit because the matching has to be done nearby the infinite impedance area of the Smith Chart. In this paper, it is studied for the output matching circuit of the microwave oscillator to get the maximum output power. The maximum output point can be found by adjusting the position of moving short in the Tuner while the oscillator is operating after connect the 3-dB coupler Tuner to the oscillator without output matching circuit. To design the oscillator for the maximum output power can be done easily with the microstrip line which is realized from the measured S-parameters of Tuner. In compare the oscillator by the existing method with another one by the suggested method in this paper, the first one has 6.45 dBm output power and second one has 9.71 dBm which is 3.26 dBm higher than the first one at the oscillation frequency 1.0338 GHz.
Transmission performance Improvement of Wireless ATM Cell in Fading Channel
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 179~190
One of the most important topics of recent years is that a multimedia technology such as wireless ATM has been introduced in radio systems for video, voice and data transmission. A major problem in such systems is the occurrence of errors due to multipath fading or interference. To combat this problem, forward error correction (FEC) coding is commonly used as a means of eliminating these errors. This paper has analyzed theoretically the effect of fading to design effective wireless ATM system. The BER, CLR, and CER of wireless ATM system adopting FEC coding and diversity reception techniques have been derived in fading environment. Also, simulations of BER and CLR have been carried out and compared with the above theoretical results.
Performance Analysis of Diversity Received DS-CDMA/MDPSK Signals in m-distribution and Rician Fading Environments
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 191~198
The error are equation of DC-CDMA/MDPSK signal has been derived in m-distribution and Rician fading channels. Predeteception multipath MRC(Maximal Ratio Combining) diversity technique is employed for improving the bit error rate performance. The suitability of modeling a Rician fading environment by properly chosen m-distribution model is examined. Using the derived equation the error performance has been evaluated and shown in figures as a function of PN code sequence length(N), user number(U), multipath number(P), fading index(m), Rician factor(K), number of diversity branches(L) and (
). The results show that the error performance in Rician fading agrees well with that in m-distribution fading as fading becomes weak and as user number(U) increases and as multipath number(P) increases and diversity number(L) increases.
The Characteristic Analysis of Wave Propagation for ICO Communication Satellite
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 199~210
It is very important to analyze and predict the propagation characteristics of LEO communication satellite at the service area using computer simulation. In this paper, the propagation characteristics of a satellite communication system are analyzed using ray tracing technique. We predicted the receiving environment and obtain the delay profile and total received power at each position using ray tracing method by changing both the azimuth and elevation angles after establishing the imaginary receiving space. The final goal of this paper is to analyze and understand the wave propagation characteristics of the satellite communication network about 2 GHz frequency band. The prediction method presented in this paper may help us to design satellite transceiver system and to construct a satellite communication network.
Analysis of Errors in Prediction Results of Ray Tracing Propagation Model for Microcellular Environments
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 211~218
In this paper, we analyze various errors in prediction results of ray tracing propagation model for microcellular environments. It is shown that improper electrical parameters of building materials and limitations of diffraction orders can cause high errors in prediction results. Especially, the effect of errors in building database on prediction results is considered in detail. It is also shown that the prediction error increases as the resolution of building map data is getting worse, and the error is analyzed depending on LOS and NLOS domains. Based on the results obtained by the analysis developed in this paper, 5 m resolution is suitable for the building map data if the maximum prediction error is required to be below 6 dB.
Design and Implementation of Voltage-controlled Oscillator for 380 MHz TRS Handset
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 219~225
A voltage controlled oscillator for the local oscillator in 380 MHz TRS handset is designed and fabricated. To improve the phase noise characteristics, the NEC's 2SC4226 transistor with NF=1.2 at 1 GHz and Toshiba's 1SV229 varactor diode with Q=70 are used. And an inductor of VCO is realized by microstrip line. At the bias condition of 5 V and 10 mA, the output power and phase noise in the operating frequency range of 357∼387 MHz are above 3.7 dBm and 111 dBc/Hz at 12.5KHz offset from the carrier, respectively. And FM sensitivity deviation are within ±0.4 KHz. This VCO is well suited for TRS handset.
Performance Improvement of Spread Spectrum Satellite Communication System in the Presence of Jamming Interference
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 226~237
In recent SATCOM systems, transparent transponders are widely used. The transponder is, however, the most vulnerable part in SATCOM systems against jamming interference. All signals within the transponder bandwidth are frequency-converted and retransmitted with IM(intermodulation) products. In this paper, the method is proposed that makes the SJR(Signal-to-Jammer ratio) better. The bandwidth spreading of the user signal can reduce the jammers effects. The geostationary satellite system is modeled to simulate and to certificate the capability of suppression of jammers by DSSS. If signal is partially-overlapped by jammer and PG(processing gain) is 16.9 [dB] for 2ASK jammer and about 16.8 [dB] for QPSK jammer, when BER is
Diffraction Anomalies on the Periodic Strip Grating over a Grounded Dielectric Layer in Case of Oblique Incidence and Arbitrary Polarization
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 238~252
Diffraction anomalies in the periodic strip grating over a grounded dielectric layer are investigated for the plane wave incidence case of both arbitrary(oblique) incidence angle and arbitrary polarization by use of the spectral domain method combined with the sampling theorem. Some numerical results for the Bragg and Off-Bragg blazing phenomena for the cases of arbitrary incidence angle and polarization as well as TE and TM polarization are presented along with discussions on those phenomena.
Design of Directional Couplers in Bilevel Microstrip Using the Least Squares Residual Method
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 253~264
In this paper, a design method for directional couplers using bilevel microstrip substrates is proposed. This kind of broadside-coupled coupler provides large coupling factors and broadband characteristics which can not be provided by conventional edge-coupled couplers. Physical dimensions needed for design are obtained by numerical analysis of characteristic parameters of the coupler using the least squares residual method, a kind of variational method, and an eigenvalue problem analysis method. A 3[dB] directional coupler is designed by the proposed method at the center frequency of 1 GHz, built, and tested. The validation and accuracy of the method are confirmed by comparing the numerical results with the experimental results.
A Study of Broadband Propagation Characteristics for The Future Mobile Communications(I) - Broadband Propagation Characteristics Measurements on Indoor
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 9, issue 2, 1998, Pages 265~277
In this paper, to investigate the possibility of fading reduction effect and high transmission rate in indoor multipath propagation environment, we measured and analyzed broadband signal conducting by frequency sweeping method in LOS(Line-of-Sight) environment. In measuring, we used vertically polarized, horizonatally polarized and circularly polarized and circularly polarized antenna to compare the fading reduction effect and the characteristic of bandwidth amplitude fluctuation between each broadband signals. As a result, it can be seen that the circularly polarized antenna can reduce the amplitude deviation of the broadband signal because it can remove the odd-times reflected wave in LOS environment. And also, It was found that the best effective diversity reception method is to use polarization branches, which install a circularly polarized antenna at the transmitting end and compose the vertical and horizontal antenna at the receiving end.