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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of electromagnetic engineering and science
Journal Basic Information
Journal DOI :
The Korean Institute of Electromagnetic Engineering and Science
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Volume & Issues
Volume 7, Issue 4 - Dec 2007
Volume 7, Issue 3 - Sep 2007
Volume 7, Issue 2 - Jun 2007
Volume 7, Issue 1 - Mar 2007
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Analog Predistortion High Power Amplifier Using Novel Low Memory Matching Topology
Kim, Jang-Heon ; Woo, Young-Yun ; Cha, Jeong-Hyeon ; Hong, Sung-Chul ; Kim, Il-Du ; Moon, Jung-Hwan ; Kim, Jung-Joon ; Kim, Bum-Man ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 147~153
DOI : 10.5515/JKIEES.2007.7.4.147
This paper represents an analog predistortion linearizer for the high power amplifier with low memory effect. The high power amplifier is implemented using a 90-W peak envelope power(PEP) LDMOSFET at 2.14-GHz and an envelope short matching topology is applied at the active ports to minimize the memory effect. The analog predistortion circuit comprises the fundamental path and the cuber and quintic generating circuits, whose amplitudes and phases can be controlled independently. The predistortion circuit is tested for two-tone and wide-band code division multiple access(WCDMA) 4FA signals. For the WCDMA signal, the adjacent channel leakage ratios(ACLRs) at 5 MHz offset are improved by 12.4 dB at average output powers of 36 dBm and 42 dBm.
Reconfigurable Multi-Band Mixer for SDR System
Kim, Jeong-Pyo ; Choi, Jae-Hoon ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 154~160
DOI : 10.5515/JKIEES.2007.7.4.154
A reconfigurable multi-band mixer for the SDR system is proposed. The proposed reconfigurable mixer is operated between
, which includes all commercial mobile communication service. Because the varactor diodes are used to select a specific frequency and to adjust the impedance characteristic of the selected frequency band, the proposed reconfigurable mixer can be achieved to similar performance across all of the tuning range. In addition, the designed reconfigurable mixer is applicable for the SDR system since it has a single signal path for the multi-band signals and wide band tuning range.
A Multi-Channel Correlative Vector Direction Finding System Using Active Dipole Antenna Array for Mobile Direction Finding Applications
Choi, Jun-Ho ; Park, Cheol-Sun ; Nah, Sun-Phil ; Jang, Won ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 161~168
DOI : 10.5515/JKIEES.2007.7.4.161
A fast correlative vector direction finding(CVDF) system using active dipole antenna array for mobile direction finding(DF) applications is presented. To develop the CVDF system, the main elements such as active dipole antenna, multi-channel direction finder, and search receiver are designed and analyzed. The active antenna is designed as composite structure to improve the filed strength sensitivity over the wide frequency range, and the multi-channel direction finder and search receiver are designed using DDS-based PLL with settling time of below 35 us to achieve short signal processing time. This system provides the capabilities of the high DF sensitivity over the wide frequency range and allows for high probability of intercept and accurate angle of arrival(AOA) estimation for agile signals. The design and performance analysis according to the external noise and modulation schemes of the CVDF system with five-element circular array are presented in detail.
An Orthogonal Phase-Superimposed Peak-to-Average Power Ratio Reduction Technique
Han, Tae-Young ; Kim, Nam ; Choi, Jung-Hun ; Lee, Jae-Hwan ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 169~174
DOI : 10.5515/JKIEES.2007.7.4.169
This paper presents a method of superimposing the rotation phases over the pilot and data symbols in order to reduce the peak-to-average power ratio(PAPR) in orthogonal frequency division multiplexing(OFDM). The phases of the rotation vector are added to those of the pilot symbols and those of the data symbols by interlaying them between any two pilot symbols. The receiver restores the data symbols by utilizing the channel estimation of the pilot symbols. Therefore, the bandwidth efficiency is improved by not using the subcarriers that are assigned for the reduction of the PAPR. Also, the enormous increase of the bit error rate which would be caused by incorrectly receiving the side information, i.e. the phases of the rotation vector, is prevented. The simulation results of the bit error rate performance for the BPSK are given using the COST-207 channel model.
Design of Reflector Type Frequency Doubler for Undesired Harmonic Suppression Using Harmonic Load Pull Simulation Technique
Jang, Jae-Woong ; Kim, Yong-Hoon ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 175~182
DOI : 10.5515/JKIEES.2007.7.4.175
In this paper, a study on the reflector type frequency doubler, to suppress the undesired harmonics, is presented. A 12 to 24 GHz reflective frequency doubler is simulated and experimented. Design procedure of the frequency doubler with reflector is provided and the frequency doubler with good spectral purity is fabricated successfully. It has harmonic suppression of the
harmonic and the
harmonic with no additional filter. And, it has conversion gain with the input power of 0 dBm over bandwidth of 500 MHz. A NEC's ne71300(N) GaAs FET is used and the nonlinear model(EEFET3) using IC-CAP program is extracted for harmonic load pull simulation. Good agreement between simulated and measured results has been achieved.
New Evaluation on the Selective Diversity Systems for the Detection of M-ary PSK & DPSK Signals over Rayleigh Fading Channels
Kim, Chang-Hwan ; Kim, Hyeong-Kyo ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 183~189
DOI : 10.5515/JKIEES.2007.7.4.183
When the M-ary signal experiences the Rayleigh fading, the diversity schemes can reduce the effect of fading since the probability that all the signals components will fade simultaneously is reduced considerably. The symbol error probabilities for various M-ary signals, such as MDPSK(M-ary DPSK) and MPSK(M-ary PSK), are mathematically derived for the Selection Combining 2(SC-2) and Selection Combining 3(SC-3) demodulation system which requires a less complex receiver than maximum ratio combining(MRC). The propagation model used in this paper is the frequency-nonselective slow Rayleigh fading channel corrupted by the additive white gaussian noise(AWGN). The numerical results presented in this paper are expected to provide information for the design of radio system using M-ary modulation method for above mentioned channel environment.
Cross-Coupled Microstrip Combline Bandpass Filter Using Stepped-Impedance Resonators
Cho, Young-Ho ; Choi, Seung-Un ; Yun, Sang-Won ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 190~194
DOI : 10.5515/JKIEES.2007.7.4.190
In this paper, a cross-coupled microstrip combline bandpass filter using stepped-impedance resonators(SIRs) is proposed. In order to improve the selectivity as well as the insertion loss, the SIR configuration is used. The cross coupling is also introduced to enhance the selectivity. The improvement of the insertion loss is demonstrated not only by deriving the quality factor of the SIR but through the measured performances. Both the proposed and the conventional combline bandpass filter with 5 % of fractional bandwidth at 2 GHz were fabricated and tested. Compared to the conventional combline bandpass filter, the proposed one exhibits the improved selectivity as well as the lower insertion loss characteristics.
Low Pilot Ratio Channel Estimation for OFDM Systems Based on GCE-BEM
Wang, Lidong ; Lim, Dong-Min ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 195~200
DOI : 10.5515/JKIEES.2007.7.4.195
Doubly-selective channel estimator for orthogonal frequency division multiplexing(OFDM) systems is proposed in this paper. Based on the generalized complex exponential basis expansion model(GCE-BEM), we describe the time-variant channel with time-invariant coefficients over multiple OFDM blocks. The time variation of the channel destroys the orthogonality between subcarriers, and the resulting channel matrix in the frequency domain is no longer diagonal, but the main interference comes from the near subcarriers. Based on this, we propose a channel estimator with low pilot ratio. We first develop a least-square(LS) estimator under the assumption that only the maximum Doppler frequency and the channel order are known at the receiver, and then verify that the correlation matrix of inter-channel interference(ICI) is a scaled identity matrix based on which we derive an optimal pilot insertion scheme for the LS estimator in the sense of minimum mean square error. The proposed estimator has the advantages of low pilot ratio and robustness against inter-carrier interference.
Analysis on SC-2 Diversity Systems for the Reception of M-ary Signals over Rayleigh Fading Channels
Kim, Chang-Hwan ; Kim, Hyeong-Kyo ;
Journal of electromagnetic engineering and science, volume 7, issue 4, 2007, Pages 201~206
DOI : 10.5515/JKIEES.2007.7.4.201
When the M-ary signal experiences the Rayleigh fading, the diversity schemes can reduce the effects of fading since the probability that all the signals components will fade simultaneously are reduced considerably. The symbol error probabilities for various M-ary signals, such as MDPSK, MPSK and MQAM, are mathematically derived for the SC-2(Selection Combining 2) demodulation system, whereby the two signals with the two largest amplitudes are coherently combined among the L branches. On the other hand, maximum ratio combining(MRC) requires the individual signals from each path to be time-aligned, cophased, optimally weighted by their own fading amplitude, and then summed. The propagation model used in this paper is the frequency-nonselective slow Rayleigh fading channel corrupted by the Additive White Gaussian Noise(AWGN). The numerical results presented in this paper are expected to provide information for the design of radio system using M-ary modulation method for above mentioned channel environment.