• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.8
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• pp.913-919
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• 2008

A new design and its experimental results of a microstrip-fed ultra-wideband tapered slot antenna(TSA) for millimeter-wave systems are presented. By utilizing the ultra-wideband microstrip-to-CPS transition(balun), ultra-wideband characteristics of the inherent TSA are retrieved. Also, the design procedure of the TSA is simplified by performing simple impedance matching between balun and antenna. The proposed TSA is shaped by using the Fermi-Dirac tapering function and corrugated at the outer edge. The implemented antenna demonstrates ultra-wideband performance for frequency ranges from 23 to over 58 GHz with the relatively high and flat antenna gain of 12 to 14 dBi and low sidelobe levels. In addition, a 4-element linear antenna array for phased-array systems and mm-wave sensor applications is also presented.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2002.11a
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• pp.407-411
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• 2002

Ternary sequences are digital codes consisting of discrete values -1, 0, and 1 only. They are advantageous in that the correlation can be carried out using additions only Also, they feature an ideal circular autocorrelation function, but in channel characterization tasks, the usual requirement is that the linear autocorrelation function be ideal, i.e., a Kronecker delta function. In this article, we consider two approaches to improving their linear autocorrelation or crosscorrelation properties: one is an inverse filtering method with theresholding and the other is a singular value decomposition (SVD) method. Both methods are simulated under noisy circumstances. The inverse filtering method resulted in an improvement in peak sidelobe level of about 1㏈ at an SNR of 30㏈, and the SVD method showed similar performances, albeit more sensitive to noise depending on the singular value selection strategy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1354-1362
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• 2015

Heterogeneous network technology is expected to be a core technology for 5G mobile communications. 5G mobile network would be composed of many base stations even have mobility, then the operator should connect base stations through the wireless backhaul technology. This paper presents Ultra Wide Area Wireless Backhaul Network System with massive array antenna. We conducted link budget analysis for Ultra Wide Area Wireless Backhaul Network and performance analysis of massive array antenna system through the transmission simulator based on beamforming technology. In wide area ($10km^2$) wireless backhaul system composed of massive antenna, we achieved 5 bps/Hz average spectral efficiency with 1 W transmission power per beam.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1121-1126
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• 2017

Various studies such as INS(: Inertial Navigation System) are conducting to estimate the position of UAV, because the GPS information of UAV is at risk like the GPS jamming. The position estimation using DoA and RTT are used to apply many radar systems, and that process can be applied in datalink of UAV. The general monopulse feed in UAV datalink is Multi-horn, because of the wide BW(: Band Width) and frequency range. And it needs wide SNR range of tracking because of the limited transmit power of airborne unit. The estimation error of position increase at low SNR, and the DoA is valid in only 3dB beam width but high SNR causes false of mainlobe detection because of large sidelobe. In this paper, We propose the method to achieve higher accuracy of DoA estimation on low SNR and review some idea that able to detect mainlobe.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.217-222
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• 2014

This paper discusses about the beam pattern distortion caused by the failures of some antenna modules in the active array antenna and analyses the possibility of improvement through applying the beam pattern compensation method previously studied. The beam pattern distortion which is mostly represented as an increase of the sidelobe level, can be suppressed through re-synthesizing each module's magnitude and phase. This method was applied to the prototype of active array antenna system, and the results of antenna pattern distortion and compensation were analyzed and measured in the Near Field Chamber. Array failures are generally divided into random TR module failures and TRU(TR Unit: combination of TR modules, Beam Computation module, Power supply module) failures. The results of beam pattern compensation were analyzed in each failure and compared to the results of the simulation. The beam pattern compensation results applied to the real active antenna array system showed the similar to the simulation results. Consequently, it was verified the beam pattern could be compensated with the magnitude and phase adjustment of other normal antenna modules.

• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.452-465
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• 2016

In this study, the structure of a concave annular array transducer was optimized to generate high intensity focused ultrasound for medical therapeutic application. The transducer has a phased array structure composed of several concentric channels that have 40 mm as the radius of curvature. We derived theoretical equations to analyze the sound field of the transducer and verified the validity of the equations by comparing the results calculated by the equations with those from finite element analyses. We also checked the possibility of dynamic focusing at around the geometric focal point. Further, the level of a grating lobe occurring at an unwanted position in the transducer sound field was confirmed to be reducible through the relation between the number of channels and the frequency of the transducer. Hence, the structure of the transducer was optimized to place the main lobe within a specific range from the zenith while systematically reducing the level of the maximum sidelobe including the grating lobe. The designed structure showed the performance better than that targeted at all the focal points.

• The Journal of the Acoustical Society of Korea
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• v.16 no.1
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• pp.47-53
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• 1997

This paper concerns an efficient approach to forming a beam pattern of a microphone array to deal with broadband signals such as speech in a teleconference. A numerical method is proposed to find updated location of sidelobes for equalizaing the sidelobes via perturbation of array parameters such as array weight or microphone spacing. Thus the microphone array is optimized in a Dolph-Chebyshev sense such that directional or background noises incident in an array visual range are eliminated efficiently. It is shown that perturbation of microphone spacing yields an optimum pattern more appropriate for dealing with broadband signals than that of array weight. Also, a novel method is proposed to find a beam pattern which is robust with respect to sidelobe in a scanning situation. Computer simulation results are presented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1A
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• pp.34-40
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• 2009

In this paper, we derive the average received beampattern at each receive node which is randomly distributed within a disk when considering a collaborative beanforming between transmission nodes which are randomly distributed within another disk for ad hoc sensor network. Numerical results show that the radius of disk at the transmitter determines the beamwidth of mainbeam, and the sidebeam is affected by the number of transmitter nodes. We also consider K receive groups and divide the transmit sensor modes into K groups to support each receive group using beamforming, and derive the SINR at each receive node. Finally, we investigate the effects of beampattern and interference on total sum capacity among all receive node, and numerically determine the number of transmit nodes for each group which can achieve the maximal sum capacity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.6A
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• pp.642-647
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• 2007

HAP(High Altitude Platform) systems have been proposed due to their unique advantages over terrestrial and satellite systems as the alternative wireless communication system to deliver the third generation IMT-2000 wireless services. It has been required to study for the power control in W-CDMA HAP system as well as the terrestrial mobile system in order to mitigate interference and increase the capacity. In this paper, a new power control has been proposed for HAP system considering the interference profile into the DB(distributed balancing) SIR(signal to interference ratio)-based algorithm which has been considered in terrestrial system, and estimated by the outage performance of the proposed DB algorithm is better remarkably than DBPA(distance-based power allocation) which is proposed for HAP system, and it is the same regardless of the antenna maximum gain and its sidelobe characteristics.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.1
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• pp.27-35
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• 1998

In this paper, we propose a novel spectral-chopping model of Class-II$(1+D)^2$ -PRS system which reveals improved spectral efficiency. We build up the model having spectrum chopped by the amount of Nyquist over-rate, and then compare its characteristics with the conventional model in both the time-domain and the frequency-domain. When the transmission system operates above the Nyquist rate, the new model has better performance than the conventional PRS using its inherent speed-tolerance. According to our investigations, Class-II PRS shows more excellent effect in the spectral-chopping method than Class- I and W types analyzed previously. We ascertain that the over-rate of 26.675 obtained by the inherent speed-tolerance could be improved upto 40% using spectrum-truncation. These effects come from the fact that the raised-cosine spectrum of Class-II PRS has smaller Boss of frequency component and energy than any other types for the same amount of truncation. In order to validate these theoretical results, we present their sidelobe-trends confirming cancellation effects at the sampling instants and some experimental results showing their patterns of eye-openings and spectra.