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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 8, Issue 6 - Dec 1997
Volume 8, Issue 5 - Oct 1997
Volume 8, Issue 4 - Aug 1997
Volume 8, Issue 3 - Jun 1997
Volume 8, Issue 2 - Apr 1997
Volume 8, Issue 1 - Mar 1997
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High Effciency Balanced Power Amplifier
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 323~331
In this paper, the high efficiency balanced amplifier is presented as high efficiency power amplifier. This amplifier is basically composed of two FETs, an input power divider, output power combiner, input matching circuits, output matching circuits, second harmonic interconnection circuit and lowpass filter. The second harmonic interconnection circuit is composed of second harmonic frequency bandpass filter and transmission line. This circuit is inserted between the output terminals of the two FEF's output matching circuit, there is a second harmonic standing wave generated between two FET outputs. The electric wall termination is equivalent to the short circuit termination. As a result, the FET output termination condition needed to attain high efficiency is realized. Experimental high efficiency balanced amplifier is constructed to determine its practically attainable efficiency. The input VSWR is 1.27, and the output VSWR is 1.18. Power added efficiency of 75% is attained at 1.75 GHz band about 3W to balanced amplifier.
Performance Analysis of Adaptive System Model using MPSK and MQAM for Frequency Nonselective Channel
Jae-Kyoung Moon ;
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 332~341
In this paper, we propose an adaptive trellis-coded Multipe Quadrature Amplitude Modulation (ATCMQAM) for slowly varying Rayleigh fading channels. The proposed system adaptively controls the coding rate combined with modulation level of pargmatic approach to trellis-coded modulation according to the instantaneous fading channel conditions, and employs MQAM as modulation scheme. Results by computer simulation show that the proposed adaptive model using MQAM can realize higher quality transmission with the improvement more than 0.5~1 bit in average bit rate, and there is a coding gain of 2~5 dB, depending on the high SNR value, compared with the conventional adaptive model employing MPSK.
Performance Evaluation of Hybrid DS/SFH-CDMA Noncoherent MFSK Signal with Channel Coding and MRC Diversity Techniques in Mobile Communication Nakagami Fading Channels
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 342~353
This paper presents an analytical evaluation of a hybrid direct-sequence/slow frequencyhopped code division multiple-access (DS/SFH-CDMA) system employing noncoherent M-ary frequency shift keying(MFSK) modulation in a multiple Nakagami fading (m) environment. Multipath interference (MPI) and multi-access interference (MAI) is taken into account and the spectral efficiency is calculated for uncoded as well as channel coding systems. Predetection multipath maximal ratio combining (MRC) diversity in conjunction with interleaved channel coding (Hamming(7,4) code, BCH(15, 7) code and RS (7, 4), (15, 9)) code ) is employed for improving the bit error rate (BER) performance. The BER of noncoherent hybrid system is obtained using a Gaussian interference approximation.
A Microstrip Antenna with a Small Loop
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 354~362
In this paper, a microstrip antenna with a small loop consisting of the left and right parallel plate to load a capacitor is proposed. It is obtained the improved high gain and bandwidth than the antenna consisting of the right parallel plate to load a capacitor on QMSA (Quarter-Wavelength Mi- crostrip Antenna). Also, the designed and manufactured antenna can receive both vertically and horizontally polarised waves to operating frequency of 1.5 GHz; therefore this is available as a small antenna for wireless telephones and will be quite useful for indoor communication.
Development of an UHF CW/FM Proximity Sensor System
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 363~372
We have developed the UHF CW/FM proximity sensor system. The UHF CW/FM Proximity Sensor is the system which recognizes the distance from the antenna to the target using the UHF band signal. To adjust sensing distance, we must change modulation frequency parameter or modulation index parameter. When we select the modulation frequency paramter for adjusting sensing distance, new modulation frequency generator and new band pass filter will be required. It is so inefficient that we choose modulation index parameters for adjusting sensing distance. In this paper, theoretical principles of the UHF CW/FM Proximity Sensor are analyzed and doppler signals for the distance from the antenna to the target are measured as the modulation index(
) being changed. Three systems of which moduation indices are 38, 50, and 61 are made. We concluded that the sensing distance will decrease as the modulation index(
) increases. It is in accord with the theory of this UHF CW/FM Proximity Sensor System.
A Study on the Design of Variable Reference Tap Position Equalizer for Synchronous Microwave Tansmission Systems
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 373~381
Digital microwave transmission systems are equipped with equalizer against fading during multipath fading. In this paper, we proposed variable reference tap position equalizer that varies the reference tap according to fading type to archive better performance. We got the performance improvement about 4~5 dB in MP condition and 2~3 dB in NMP condition from simulation results.
A Stydy on the Development of 800 MHz band Pass Fiters using Polycrystal AIN Film
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 382~389
We present the results on the applicability of the polycrystalline AIN thin films for a surface acoustic wave filter operating at 800 MHz frequency. The films show the FWHM of 3 .deg. from th X-ray rocking curve, which indicates that the c-axis of the films is pre- ferentially oriented along the growth direction. The fabricated band pass filters exhibit the center frequency of 865 MHz with 3dB band-width of 45 MHz. From the measured frequency response, the electro-mechanical coupling constant of 0.8% and the SAW velocity of 5,709 m/s are obtained. Thus, we conclude that the sputtered AIN films are feasible for the fabrication of uper UHF band SAW filters.
Measurements and Statistical Modeling of Ignition Noise from Vehicle
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 390~402
The ignition noises from the vehicle are measured and the measurement data are statistically treated for modeling. The low-noise amplifier and band-pass filter are added between the receiver and the three axes antenna for low noise level measurement and the APD and PSD are measured in 800 MHz frequency range. The measured APD curves can be expressed in terms of sensitivity study of each model through 3(class A) or 6(Class B) parameters variation, and these optimal parameter can easily be calculated by using the Composite Approximation Algorithm. The selected APD parameter can be used for making the Data Base EM-environments and also applied to determine the output and sensitivity margin for the transmitter and receiver. 'Digital microwave transmission systems are equipped with equalizer against fading during multipath fading. In this paper, we proposed variable reference tap position equalizer that varies the reference tap according to fading type to archive better performance. We got the perf？mance improvement about 4~5 dB in MP condition and 2~3 dB in NMP condition from simulation results.
The Analysis of the Effect on the Wave Propagation of DBS Signal by the Space Debris for Satellite Communication
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 403~414
The distribution of the space debris caused by any source affects the DBS & FSS wave propagation for satellite communication. In this paper, the normalized expansion coefficients are evaluated with varying the volume distribution density of space debris and the operating frequency, and then the attenuation and phase shift are calculated by using the normalized expansion coefficients. Conclusively, the attenuation and phase shift are mostly affected with the real and imaginary part of the amplitude function, respectively, which represented by electric field component of the Bessel function. The results of this paper adapted for the design of the link budget for satellite communication system and the reconsideration of space environment as the space debris increses by geometric progression.
FH/GMSK System using DDS
The Journal of Korean Institute of Electromagnetic Engineering and Science, volume 8, issue 4, 1997, Pages 415~425
Although FHSS has many advantages over conventional digital radio communication system, field application has been so far hampered due to its complicated synchronization. In this paper, a new FHSS system is proposed which one FH signal modulated with GMSK and one chip delayed FH signal than former are sent from transmitter, and this is recovered by matching process at a heterodyne correlator in receiver; thus eliminates synchronization as a whole. Through analysis and experiment, we assure that there is possibility in this. The exper- imental result from 915~929 MHz bandwidth with 31 chips is investigated in the environment of AWGN.