• Journal of the Institute of Electronics Engineers of Korea TC
• /
• 제40권2호
• /
• pp.47-55
• /
• 2003

In this paper, the performance of DS-CDMA system with smart antenna is analyzed for different bandwidths (1.25MHz,5MHz) and different channel environments (rural, urban) in wideband multipath channel. For the analysis of smart antenna system, the vector channel having the spatio-temporal correlation is modeled as a time-variant linear filter in time, and each multipath is assumed as a reflective wave from only one direction (only one cluster) in space. Several multipath is within one chip are distingushed into each one and the strongest signal is selected, DS-CDMA system with smart antenna using wider bandwidth present better performance than that using narrow bandwidth. It is shown that the smart antenna is more effective in urban area when using 2D-RAKE receiver.

• Journal of Navigation and Port Research
• /
• 제26권5호
• /
• pp.525-528
• /
• 2002

The proposed EMC filter composed with feed-through capacitors and ferrite beads of high permeability was prepared which satisfy the EMC standard for a wide-band noise signal in the frequence of 10 MHz to 1.5 GHz in power supply line. The optimum structure of ferrite bead was found by calculating the load effect of ferrite beads. As a result, the filter showed excellent differential- and common-mode noises filtering characteristics above 30dB in the frequency band from 10 MHz to 1.5 GHz. The immunity characteristics are improved more than 10 to 30 dB over the frequency band from DC to 1.8GHz.

• Journal of Satellite, Information and Communications
• /
• 제6권2호
• /
• pp.72-77
• /
• 2011

Spectrum sensing is a critical functionality of CR network; it allow secondary user to detect spectral holes and to opportunistically use under-utilized frequency bands without causing harmful interference to primary use. Recently, wideband service has been increase for processing abundance of data traffic. So CR network needs a realizable implementation design of spectrum sensing for wideband. To get high resolution performance of wideband sensing must precede algorithm processing for reliability signal detection. By the way, the performance of spectrum sensing can be degraded due to fading and shadowing. In order to overcome this problem, we propose system model of wideband sensing scheme on energy detected collaborative technique. we divide wideband into narrowbands and use narrowbands to detect signal excepting some narrowbands including bad channel through the CSI. And we simulate and analyze in terms of detection probability with various SNR.

• The Journal of the Acoustical Society of Korea
• /
• 제38권2호
• /
• pp.145-153
• /
• 2019

Adaptive beamforming methods are known to suppress sidelobes and improve detection performance of weak signal by constructing weight vectors depending on the received signal itself. A standard adaptive beamforming like the MVDR (Minimum Variance Distortionless Response) is very sensitive to mismatches between weight vectors and actual signal steering vectors. Also, a large computational complexity for estimating a stable covariance matrix is required when wideband beamforming for a large-scale array is used. In this paper, we exploit the WBRCB (Wideband Robust Capon Beamforming) method for stable and robust wideband adaptive beamforming of a passive large uniform line array sonar. To improve robustness of adaptive beamforming performance in the presence of mismatches, we extract a optimum mismatch parameter. WBRCB with extracted mismatch parameter shows performance improvement in beamforming using synthetic and experimental passive sonar signals.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• 제17권1호
• /
• pp.59-66
• /
• 2024

In this paper, the method to design the antenna, which is suitable for an impulse-like waveform radiation, is presented. In general, the impulse-like waveform has its spectrum of around sub GHz bandwidth and the antenna should be properly designed for not only operating wide-bandwidth also reflecting the time domain characteristics for near-zone impulse radar applications. In this regard, Vivaldi antenna has been designed and characterized in terms of short-pulse radiating aspects in the time domain and verified by measured results. The designed antenna has shown to be operating within wide-bandwidth and to be stable for the input impedance from 1.8 to more than 10GHz. The far-zone radiating waveform has been investigated on each plane at the interval of 30degree and the designed antenna has shown to be a directive characteristic. It can be seen that those results proposed are widely applicable to the near area sensing applications such as ground-penetrating radar.

• Journal of the Institute of Convergence Signal Processing
• /
• 제6권2호
• /
• pp.100-106
• /
• 2005

OFDM is one of the promising modulation candidates for a fourth generation broadband mobile communication system because of its robustness against inter-symbol inteference(ISI). The OFDM transmission technique has the inherent flexibility to adapt the modulation scheme on each subcarrier according to the signal-to-noise ratio(SNR). In this paper, the adaptive modulation scheme of OFDM system is proposed in broadband mobile channel. The proposed algorithm allocates initially the number of bits in each subcarrier using the threshold SNR according to the target BER and controls the total number of target bits using the well-known algorithm of Chow et al. In addition, the subcarriers of the proposed algorithm are clustered in blocks, that the signalling overhead can be reduced for the bit allocation of subcarriers. For the simulated experiments, this paper presents an evaluation for the effects of target BER, the various numbers of subcarriers in the subband block, and Doppler frequency on the performance of adaptive OFDM in broadband mobile channel.

• The Journal of the Korea institute of electronic communication sciences
• /
• 제4권3호
• /
• pp.183-189
• /
• 2009

In this paper, we propose RF front-end architecture using hybrid conversion method to receive broadband signal. The validity is verified by design, fabrication and experiment. The proposed RF front-end architecture due to up-conversion block improves the deficiency of performance deterioration to be generated through harmonic signal and image signal conversion in the conventional RF front-end, and improves the deficiency of the complexity that is from to adopt a multiple local oscillators for the generation of wideband LO signal in the conventional RF front-end by applying the principle that tuning bandwidth is multiplied at sub-harmonic mixer. Manufactured circuits satisfy the deduced design specification and target standard with gain above 80 dB, noise figure below 6.0 dB and IIP3 performance above -5.0 dBm for the condition of the minimum gain in RF front-end.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• 제21권11호
• /
• pp.2206-2212
• /
• 2017

When it comes to naval surface warfare, the probability of detection is an important factor in survivability and the Radar Cross Section(RCS) is a major parameter. In this paper, the RCS reduction technology of the Radar Absorbing Material(RAM) method is carried out for the general frequency range for naval warfare. We set the analysis model with the simplified ship model and the wide band metamaterial which is high-tech radar absorbing materials is selected for the RAM method. The modeling of the wide band metamaterial composed of an MIK surface which has the wide band resonant properties and flexible substance and the electromagnetic absorptions and reflections of the wide band metamaterial has been simulated to explore the performance. Also, the wide band metamaterial is compared with the paint absorber to analyze RCS reduction in terms of RCS values.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• 제12권7호
• /
• pp.1160-1164
• /
• 2008

This paper presents an wideband stripline balun. And, the proposed balun is composed of one power divider and two phase converters on stripline substrate. The target characteristics of the proposed balun is the combination loss of below -0.05 dB, an amplitude imbalance of ${\pm}0.5\;dB$ and a phase imbalance of $180{\pm}10$ degrees, with the reflection coefficient(S11) of below -10 dB over frequencies ranging from 500 to 1500 MHz. The fabricated balun occupies the area of $12(W){\times}220(L){\times}2.3(T)\;mm3$. Experimental measurement shows that the fabricated balun has an amplitude imbalance of ${\pm}0.7\;dB$, a phase imbalance of $180{\pm}8$ degrees and an insertion loss of about -2 dB with the reflection coefficient(S11) of below -10 dB over frequencies ranging from 500 to 1,500 MHz.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제35권6A호
• /
• pp.611-621
• /
• 2010

When an enemy platforms transmit electronic jamming or tracking interference signal to a friendly ship's radar, the radar have to avoid the jamming and to track targets continually without losing the targets with the electronic protection techniques. Electronic protection is an essential key for a platform to survive in electronic warfare, for this purpose, jamming simulator was developed to provide electronic warfare environments for the test and evaluate the effectiveness of radar's electronic protection techniques. Jamming simulator has ability to generate a variety of deception and noise jamming signals using the DRFM which minimize phase distortions of 1GHz broadband radar signal with the phase sampling method. This paper presents the design contents of the jamming simulator to process the analysis of broadband radar signal and generate jamming signal, also proposes the algorithms of the deception and noise jamming and verifies the effectiveness of the simulator by field trial.