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      • Low-profile antenna for millimetre-wave chip-to-chip communication

        IET 2016 IET microwaves, antennas & propagation Vol.10 No.12

        <P>Here, the authors report a low-profile antenna for millimetre-wave chip-to-chip communication. The height of the proposed antenna is limited to 0.18 mm, 1/20 wavelength at 80 GHz. To realise such a low profile, a zeroth-order resonator antenna with a periodic array of four unit cells was employed, and its geometry was optimised using a full-wave simulation tool to cover an 8 GHz bandwidth from 76 to 84 GHz. With this, the antenna was capable of radiating in the end-fire direction parallel to the board length despite the short distance between the ground and the radiator. Simulation and measurement results showed that the optimised design had low reflection coefficients and consistent radiation patterns throughout the target bandwidth.</P>

      • Design of patch loaded with metallic posts inside dielectric resonator antenna

        Kim, Tae-Wan,Aziz, Rao Shahid,Park, Seong-Ook IET 2017 IET microwaves, antennas & propagation Vol.11 No.10

        <P>A new hybrid-antenna that is capable of wide-bandwidth operation and is small size is presented. The structure of the proposed antenna consists of a cylindrical dielectric resonator, metallic posts that are embedded in the resonator, and a rectangular patch. The proposed design generates three resonances: the full-cylindrical HE11, half-HE11-like mode, and radiation by the patch antenna. An electromagnetic analysis using a finite integration method (CST microwave studio) was performed to investigate the resonances. Furthermore, a prototype of antenna has fabricated for the experimental verification. The simulation results are in close agreement with the experimental findings. The proposed antenna offers a fractional bandwidth of 16.5% at the centre frequency of 9.27GHz and a peak gain is >4.56dBi in the matching band.</P>

      • Simplified log likelihood ratio calculation in soft ordered successive interference cancellation for multiple-input multiple-output digital video broadcasting-second generation terrestrial receivers

        In-Woong Kang,Young-Jun Lee,Youngmin Kim,Jae Hyun Seo,Heung Mook Kim,Hyoung-Nam Kim IET 2014 IET COMMUNICATIONS Vol.8 No.18

        <P>This study proposes a soft ordered successive interference cancellation (OSIC) receiver accompanied by a simplified log-likelihood ratio calculation method for a dual-polarised multiple-input multiple-output (MIMO) digital video broadcasting-second generation terrestrial system. The future terrestrial transmission systems will be required to provide high data rates for ultra-high definition television service. For this purpose, dual-polarised MIMO techniques with a little cross-antenna interference and high-order modulation schemes have been considered. As the cross-antenna interference needs to be removed, a soft OSIC receiver can be used effectively. However, the receiver has to endure high computational complexity for calculating soft values. To reduce it, the authors simplified the calculation based on the decision threshold (DT) method. The main contribution of this study is to extend the conventional DT method, which is restricted to only low-order modulations, to an algorithmic process applicable to any modulation order. The proposed soft OSIC receiver has about 1 dB degradation from the soft OSIC receiver with the maximum-likelihood calculation of soft values. The degradation can be fully rewarded by the significantly reduced computational complexity. Furthermore, this study presents an additional possibility of improving the decoding performance by modelling the OSIC equaliser as a biased estimator.</P>

      • Model predictive control method for CHB multi-level inverter with reduced calculation complexity and fast dynamics

        Kim, Igim,Chan, Roh,Kwak, Sangshin IET 2017 IET electric power applications Vol.11 No.5

        <P>Finite control set model predictive control (MPC) method needs calculations corresponding to the total number of voltage vectors made by power converters. This operating principle of the MPC leads to an increase in the computational load and number of calculations, which dramatically increase proportional to the increase in the level of cascaded H-bridge (CHB) inverters. However, it is difficult to consider all voltage vectors to find the optimal vector for high-level CHB inverters because of the short sampling time. This study proposes a new MPC algorithm to reduce the number of calculations for multi-level CHB inverters, in which only three voltage vectors are considered as optimal vectors regardless of the level of CHB inverters. Consequently, compared with the conventional MPC method for CHB inverters, the proposed MPC method requires fewer calculations and reduces the computational load without affecting the system performance and dynamic response.</P>

      • Relay selection Algorithm for wireless cooperative networks: a learning-based approach

        Jadoon, Muhammad Awais,Kim, Sunghwan IET 2017 IET COMMUNICATIONS Vol.11 No.7

        <P>Relay selection in cooperative communication is a crucial task for achieving the spatial diversity since the improper relay selection can decrease the overall capacity of the network. In this study, the authors use a reinforcement learning technique, called as Q-learning (QL), to solve the relay selection problem. They propose a 'QL-based relay selection algorithm' (QL-RSA) for wireless cooperative networks that maximises the total capacity of the network. QL-RSA receives the reward (feedback) in terms of the capacity by learning a multi-node amplify-and-forward cooperative environment with time-varying Rayleigh fading channels. The advantages of QL-RSA are that it is less complex, requires less channel feedback information and it is distributed in a multiple-sources environment as it provides each source a self-learning capability to find the optimal relay without exchanging information with other source nodes.</P>

      • Empirical cross-correlation modelling of multiple-input–multiple-output channel considering outdoor building density

        Jeong, Won Ho,Jung, Myoung-won,Kim, Kyung-Seok IET 2017 IET COMMUNICATIONS Vol.11 No.11

        <P>This study presents cross-correlation of building density in outdoor environments for fifth generation mobile communications at 781MHz. To avoid interference from Korean digital television (DTV) broadcasting, the authors measured the radio characteristics on Jeju Island using a channel sounder and four-by-four antennas. They derived basic large-scale parameters (LSPs) such as path loss, delay spread, angular spread, and Rician K-factor from eight different sites. The real building standing area was estimated with a geographic information system database. They propose an empirical model from analysis of the correlations between LSPs and building density. This model indicates that building density is not determined by measurement scenario such as urban, suburban, and rural. The proposed model only reflects change in building density for an outdoor environment. Finally, they verify their model through ray-tracing simulation similar to a real environment. This model can be useful in the design of future mobile communications systems according to changes in building density.</P>

      • Power-aware floorplanning-based power through-silicon-via technology and bump minimisation for three-dimensional power delivery network

        Jang, Cheoljon,Chong, Jongwha,Kim, Jaehwan IET 2014 IET COMPUTERS AND DIGITAL TECHNIQUES Vol.8 No.5

        <P>Three-dimensional (3D) integrated circuits, which use a vertically stacked design of 2D planar chips in a 3D arrangement using through-silicon-via (TSV) technology have been developed to minimise chip footprint, enable higher integration density, decrease power consumption and reduce fabrication cost. Floorplanning without considering power can increase the number of power TSVs and bumps needed to solve IR drop constraint in 3D power delivery network. In this study, the authors propose a methodology for minimising the power TSVs and bumps based on power-aware floorplanning using specific power patterns to solve IR drop constraint on the 3D power delivery network. The authors' methodology moves high power-consuming blocks to the dedicated pattern area which is able to minimise the number of power TSVs and bumps while solving the IR drop constraint. The simulation results show that the proposed method can reduce the total number of power TSVs and bumps by 13.7 and 12.2%, respectively, after power-aware floorplanning while solving the IR drop constraint.</P>

      • Modified simultaneous iterative reconstruction technique for fast, high-quality CT reconstruction

        Bappy, D.M.,Jeon, Insu IET 2017 IET image processing Vol.11 No.9

        <P>Recent advances in computational power have made it possible to use iterative reconstruction (IR) algorithms in clinics for computed tomographic (CT) imaging. Many researchers prefer IR methods to analytical methods because they reduce radiation, image noise, and artefacts. Simultaneous Iterative Reconstruction Technique (SIRT) reduces the number of views needed for CT reconstruction. However, reconstructed images include ray artefacts that can make diagnosis difficult. This study proposes a modified IR algorithm for fast, high-quality CT reconstruction. The modified method incorporates geometric non-linear diffusion in the reconstruction estimate to minimise ray artefacts. This method also converges the algorithms into global minima much faster than other methods, using the minimum number of iterations. To meet the high computational demand of improved IR algorithms, a graphics processing unit was used in this study. The authors expect that the proposed technique can be used to reconstruct high-quality CT images faster and with minimal iterations.</P>

      • Combined shape and feature-based video analysis and its application to non-rigid object tracking

        Kim, T,Lee, S,Paik, J IET 2011 IET image processing Vol.5 No.1

        <P>Many video object tracking systems use block matching algorithm (BMA) because of its simple computational structure and robust performance. The BMA, however, exhibits fundamental limitations resulting from non-rigid shapes and similar patterns to the background. The authors propose a combined shape and feature-based non-rigid object tracking algorithm, which is tightly coupled with an adaptive background generation to overcome the limit of block matching. The proposed algorithm is robust to the object's sudden movement or the change of features. This becomes possible by tracking both feature points and their neighbouring regions. Combination of background and shape boundary information significantly improves the tracking performance because the target object and the corresponding feature points on the boundary can be easily found. The shape control points (SCPs) are regularly distributed on the contour of the object, and the authors compare and update the centroid during the tracking process, where straying SCPs are removed, and the tracking continues with only qualified SCPs. As a result, the proposed method becomes free from potential failing factors such as spatio-temporal similarity between object and background, object deformation and occlusion, to name a few. Experiments have been performed using several in-house video sequences including various objects such as a moving robot, swimming fish and walking people. In order to demonstrate the performance of the proposed tracking algorithm, a number of experiments have been performed under noisy and low-contrast environment. For more objective comparison, performance evaluation of tracking surveillance 2002 data sets were also used.</P>

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