bluuebunny/crossref_metadata_2025 huggingface dataset:
Consensus of nonlinear multi‐agent systems with adaptive protocols
Authors: Wang Lei , Feng Wei‐jie , Chen Michael Z.Q. , Wang Qing‐guo
Published: July 2014

This study is concerned with the problem of dynamical distributed consensus for multi‐agent systems with nonlinear dynamics. Following the nearest neighbour rule, an adaptive consensus protocol is designed for such systems without using any global information, where the coupling weight of an agent from its neighbours adaptively updates according to the differences from the mean activity of the agent and its neighbours. The analysis shows that, under some mild assumptions, the adaptive law can achieve local and global consensus for any network with connected communication graph. Numerical simulations, illustrated by a common second‐order consensus example, are performed to demonstrate the effectiveness of the presented results.
A nonmonotonically decreasing relaxation approach of Lyapunov functions to guaranteed cost control for discrete fuzzy systems
Authors: Chen Ying‐Jen , Tanaka Motoyasu , Inoue Kohei , Ohtake Hiroshi , Tanaka Kazuo , Guerra Thierry Marie , Kruszewski Alexandre , Wang Hua O.
Published: July 2014

This study presents a nonmonotonically decreasing relaxation approach of Lyapunov functions to guaranteed cost control for discrete Takagi–Sugeno (T–S) fuzzy systems. First, the authors summarise the previous results on a relaxation of nonmonotonically decreasing of Lyapunov functions, and newly derive one lemma based on the previous results. Based on the newly derived lemma, they propose guaranteed cost control design for discrete T–S fuzzy systems. The design conditions can be represented in terms of linear matrix inequalities and provide more relaxed results than the existing approach. A design example is included to demonstrate the relaxation effectiveness of the proposed approach in guaranteed cost control.
Finite‐time boundedness of switched delay systems: the reciprocally convex approach
Authors: Wang Yijing , Liu Yuhua , Zuo Zhiqiang
Published: July 2014

This study is concerned with the problem of finite‐time boundedness analysis for switched delay systems with the average dwell time. By combining the Jensen inequality and the reciprocally convex approach, a sufficient condition is derived to guarantee the finite‐time boundedness of switched linear systems subject to time‐varying delays. It is shown that the obtained result can achieve better performance comparing with the previous ones. Finally, simulation examples are provided to demonstrate the theoretical results.
Review of person re‐identification techniques
Authors: Saghafi Mohammad Ali , Hussain Aini , Zaman Halimah Badioze , Saad Mohamad Hanif Md.
Published: July 2014

Person re‐identification across different surveillance cameras with disjoint fields of view has become one of the most interesting and challenging subjects in the area of intelligent video surveillance. Although several methods have been developed and proposed, certain limitations and unresolved issues remain. In all of the existing re‐identification approaches, feature vectors are extracted from segmented still images or video frames. Different similarity or dissimilarity measures have been applied to these vectors. Some methods have used simple constant metrics, whereas others have utilised models to obtain optimised metrics. Some have created models based on local colour or texture information, and others have built models based on the gait of people. In general, the main objective of all these approaches is to achieve a higher‐accuracy rate and lower‐computational costs. This study summarises several developments in recent literature and discusses the various available methods used in person re‐identification. Specifically, their advantages and disadvantages are mentioned and compared.
Face recognition: handling data misalignments implicitly by fusion of sparse representations
Authors: Proença Hugo , Neves João , Briceño Juan
Published: July 2014

Sparse representations for classification (SRC) are considered a relevant advance to the biometrics field, but are particularly sensitive to data misalignments. In previous studies, such misalignments were compensated for by finding appropriate geometric transforms between the elements in the dictionary and the query image, which is costly in terms of computational burden. This study describes an algorithm that compensates for data misalignments in SRC in an implicit way, that is, without finding/applying any geometric transform at every recognition attempt. The authors' study is based on three concepts: (i) sparse representations; (ii) projections on orthogonal subspaces; and (iii) discriminant locality preserving with maximum margin projections. When compared with the classical SRC algorithm, apart from providing slightly better performance, the proposed method is much more robust against global/local data misalignments. In addition, it attains performance close to the state‐of‐the‐art algorithms at a much lower computational cost, offering a potential solution for real‐time scenarios and large‐scale applications.
Multifractal based return interval approach for short‐term electricity price volatility risk estimation
Authors: Liu Weijia , Chung Chi Yung , Wen Fushuan
Published: July 2014

With the ever‐increasing penetration level of renewable energy generation in a power system, more uncertainties are introduced and hence risk management in the electricity market associated is becoming a more difficult issue for a market participant in the context of optimising his/her portfolio. Among a lot of risk factors in the competitive electricity market environment, the highly volatile electricity price contributes most to the financial risk of the power portfolio, especially in a short‐term risk management scenario such as the spot market and real‐time balancing market. Some research work has shown that the fluctuations of electricity prices exhibit multifractal characteristics, but less work has been done on the price volatility risk evaluation based on the multifractal theory. This study hence examines the feasibility of applying the multifractal theory to analyse the electricity price fluctuation, and applies the multifractal theory for evaluating the financial risk caused by electricity price volatility. A modified return interval approach considering the parameters of multifractal characteristics is employed to estimate the value‐at‐risk (VaR) of the electricity price. The fluctuant electricity price data series in the Pennsylvania‐New Jersey‐Maryland energy market are employed to demonstrate the effectiveness of the proposed VaR estimation method for short‐term electricity price volatility risk evaluation.
Fast security and risk constrained probabilistic unit commitment method using triangular approximate distribution model of wind generators
Authors: Yu Peng , Venkatesh Bala
Published: July 2014

Wind energy is intermittent and uncertain. This uncertainty creates additional risk in the day‐ahead 24‐h dispatch schedule. Wind speed can be forecasted for the next 24‐h and hourly power forecasts can be best described using probabilistic models. Security and risk constrained probabilistic unit commitment (SRCPUC) algorithms considering probabilistic forecast models of wind power can be used to optimally schedule conventional and wind generation to minimise the total cost and minimise risk. However, inclusion of non‐linear probabilistic forecast models in a SRCPUC algorithm is computationally very challenging. In this study, the proposed SRCPUC algorithm uses a triangular approximate distribution (TAD) model to probabilistically represent power output of wind generator. The TAD model quantifies hourly potential risk because of expected energy not served (EENS) from uncertain wind power. Reserves are optimally scheduled to counter EENS. Total energy cost, reserve cost and risk from EENS are minimised in the proposed SRCPUC algorithm. The proposed algorithm is implemented on 6‐bus and 118‐bus IEEE systems. The results are compared with classical enumeration technique. Significant benefits in computing time (more than 500 times faster) are seen while the numerical results are observed to be highly accurate.
Energy management and operation modelling of hybrid AC–DC microgrid
Authors: Teimourzadeh Baboli Payam , Shahparasti Mahdi , Parsa Moghaddam Mohsen , Haghifam Mahmoud Reza , Mohamadian Mustafa
Published: July 2014

Hybrid AC–DC microgrid is introduced as the future distribution network to utilise both benefits of alternative and direct currents. In such hybrid microgrid, AC and DC loads, renewable‐based distributed generators (DGs), controllable DGs and energy storage systems are connected through separate AC and DC links. An up–down operation model of such hybrid microgrid is proposed which consists of system‐ and device‐level. In the system‐level, a mixed integer linear model is suggested to balance the generation and load considering the interconnection of AC and DC subgrids for minimising total operating cost of the system in a 24‐hour period. In the device‐level, a controller is suggested for power converter‐based resources (i.e. intergrid inverter and battery) for controlling the voltage variations in AC and DC subgrids. The effectiveness of the proposed up–down operation model is demonstrated through simulation studies on a test hybrid microgrid.
Research on size and location of distributed generation with vulnerable node identification in the active distribution network
Authors: Zhao Yuanyuan , An Yiran , Ai Qian
Published: July 2014

This study aims to solve for the optimal location and capacity of distributed generation (DG), taking vulnerable node identification into consideration, in active distribution networks (ADN). Vulnerable nodes exist in the distribution network. Considering that the power fluctuations of those vulnerable nodes will have a significant impact on other nodes, the allocations of the DGs should avoid such nodes. Therefore vulnerable node identification and removal from the network can greatly limit the siting range of DGs. In this study, the vulnerable nodes are identified based on the small‐world network theory, which is used as the preliminary location of the DG. Then, a genetic algorithm (GA) is proposed to finally address the optimal location and capacity for grid‐connected DG. A GA with voltage boundary constraints is utilised to effectively prevent the bus voltage from reaching its boundary. This method improves the calculation efficiency greatly and is therefore suitable for flexible distribution network topology in ADN. According to the change of the distribution network topology, the corresponding optimal location and capacity limit for the DG can be quickly calculated. Some examples validate the algorithm and prove that it has fast convergence.
Adaptive load shedding scheme to preserve the power system stability following large disturbances
Authors: Abedini Moein , Sanaye‐Pasand Majid , Azizi Sadegh
Published: July 2014

Following large disturbances, the conventional under frequency load shedding (UFLS) relays may not operate properly, as they are designed to merely preserve the frequency stability of the system, independent of its voltage stability. In this study, an adaptive load shedding scheme is proposed to maintain the power system stability when the conventional scheme fails. In doing so, the frequency and its falling rate along with a properly defined voltage falling rate are exploited to determine closeness to the disturbance area and its severity. Accordingly, a proper amount of load is shed from the locations with the highest influence on the system stability. The proposed scheme exclusively utilises locally measured quantities and does not require a communication link. The associated logic is practical and can be easily appended to the existing UFLS relays to enhance their performance. To demonstrate the efficiency of the proposed UFLS scheme, it is applied to two large‐scale power systems where the exact load model is taken into account. The obtained results verify that a large number of blackouts because of inappropriate operation of conventional UFLS relays can be prevented using the proposed scheme.
Unlocking the benefits of real‐time thermal ratings through probabilistic power network planning
Authors: Greenwood David Michael , Taylor Philip Charles
Published: July 2014

Real‐time thermal ratings (RTTRs) is an emerging technique used to calculate the rating of electrical conductors based on local, real‐time weather conditions; this leads to an increased rating with respect to conventional approaches the majority of the time, and can be used to increase the energy yield of distributed generators, support the network during outages and defer network reinforcement. Unfortunately it is not presently recognised in network planning, design and security of supply standards. This represents a barrier to utilising RTTRs in power networks, and must be addressed. This study presents a new, probabilistic method for accounting for the variable ratings during network planning. This is coupled with an analysis of the risk of being unable to supply customers in a network adopting variable ratings, compared with the risk in the same network using conventional ratings; hence the method proposed in this study allows additional load to be connected to the network at a quantified level of risk. Finally, this method could be applied to other emerging network technologies and techniques such as demand side management or energy storage.
Max–min fair Financial Transmission Rights payment‐based AC optimal power flow locational marginal price decomposition
Authors: Bharatwaj V. Naren , Abhyankar Abhijit R.
Published: July 2014

The decomposition of locational marginal price obtained from AC optimal power flow is disputable because of its dependency on the choice of energy reference. The dispute arises because the difference of congestion component, on which the Financial Transmission Rights (FTR) payments are made, is not constant and depends on the energy reference. Prior art aimed at obtaining reference‐independent decomposition. The authors look at this dispute as a fairness issue and formulate the decomposition as a fairness problem. The fairness issue is addressed by invoking max–min fairness criteria which ensures that the FTR payment (FP) received (made) is not at the expense of other ill‐positioned FTR holders. Max–min fairness algorithm is used to arrive at an energy reference choice that aims at maximising the FP of each FTR. This in turn ensures that revenue received (payment made) is the maximum (minimum) possible under the set of constraints, without adversely affecting the FP of other FTR holders. Results on PJM 5 bus and IEEE 30 bus systems indicate that a fair solution is indeed possible.
Hyperbolic tangent function‐based least mean‐square control algorithm for distribution static compensator
Authors: Singh Bhim , Dube Sunil Kumar , Arya Sabha Raj
Published: July 2014

A variable learning rate least mean‐square (LMS) based on hyperbolic tangent function is used to enhance the rate of convergence and to suppress the existing noise in the system for the control of distribution static compensator (DSTATCOM) consisting of a three‐leg voltage source converter (VSC) with a zig‐zag transformer to eliminate the significant neutral current caused by non‐linear unbalanced loads in a three‐phase four‐wire supply system. Simulation is made for the proposed control algorithm in three‐phase four‐wire DSTATCOM system and its performance is compared with the conventional Adaline‐based LMS control algorithm. It is also shown that the convergence rate of the proposed control algorithm is quite faster in comparison with the conventional control algorithm. A prototype of DSTATCOM is developed and the real‐time implementation of the proposed control algorithm is performed on a digital signal processor. Test results have demonstrated the satisfactory performance of DSTATCOM with the proposed control algorithm under linear and non‐linear loads.
Texture and edge preserving multiframe super‐resolution
Authors: Turgay Emre , Akar Gozde B.
Published: July 2014

Super‐resolution (SR) image reconstruction refers to methods where a higher resolution image is reconstructed using a set of overlapping aliased low‐resolution observations of the same scene. Although edge preservation has been a widely explored topic in SR literature, texture‐specific regularisation has recently gained interest. In this study, texture‐specific regularisation is handled as a post‐processing step. A two stage method is proposed, comprising multiple SR reconstructions with different regularisation parameters followed by a restoration step for preserving edges and textures. In the first stage, two maximum‐a‐posteriori estimators with two different amounts of regularisation are employed. In the second stage, pixel‐to‐pixel difference between these two estimates is post‐processed to restore edges and textures. Frequency selective characteristics of discrete cosine transform and Gabor filters are utilised in the post‐processing step. Experiments on synthetically generated images and real experiments demonstrate that the proposed methods give better results compared with the state‐of‐the‐art SR methods especially on textures and edges.
Removing Gaussian noise for colour images by quaternion representation and optimisation of weights in non‐local means filter
Authors: Chen Beijing , Liu Quansheng , Sun Xingming , Li Xu , Shu Huazhong
Published: July 2014

In this study, a new quaternion filter for removal of Gaussian noise in colour images is presented. It is based on the quaternion representation of colour images and the optimisation of a tight bound of the quaternion mean‐square error between the restored colour image and the original one, together with the essential idea of the non‐local means filter. The optimal weights are obtained by using the method of Lagrange multipliers. The authors' quaternion optimal weights non‐local means filter is given by the weighted means of the observed quaternion representation using the optimal weights. Experiments on commonly used images are provided to illustrate the efficiency of the proposed filter.
Robust registration of partially overlapping point sets via genetic algorithm with growth operator
Authors: Zhu Jihua , Meng Deyu , Li Zhongyu , Du Shaoyi , Yuan Zejian
Published: July 2014

Recently, genetic algorithm (GA) has been introduced as an effective method to solve the registration problem. It maintains a population of candidate solutions for the problem and evolves by iteratively applying a set of stochastic operators. Accordingly, a key question is how to reduce the population size. In this study, the authors present two techniques for reducing the population size in the GA for registration of partially overlapping point sets. Based on the trimmed iterative closest point algorithm, they introduce a growth operator into the GA. The growth operator, which is also inspired by the biological evolution, can improve the GA efficiency for registration. Furthermore, they present a technique called centre alignment to confirm the value range of all the registration parameters, which can reduce the search space and allow the well‐designed GA to directly solve the registration problem. Experimental results carried out with the m‐dimensional point sets illustrate its advantages over previous approaches.
Synthetic aperture radar image segmentation using fuzzy label field‐based triplet Markov fields model
Authors: Wang Fan , Wu Yan , Fan Jianwei , Zhang Xue , Zhang Qiang , Li Ming
Published: July 2014

The recently proposed triplet Markov random fields (TMF) model is very suitable for dealing with non‐stationary image segmentation. However, influenced by multiplicative speckle noise, synthetic aperture radar image (SAR) is dim and blurred in the boundaries of different areas, making it difficult to locate boundary accurately in the segmentation process. Thus, in this study, the authors propose a new segmentation algorithm using fuzzy label field‐based TMF model for SAR images. In the proposed algorithm, the value of each site in the label field is extended from a finite discrete set in the classical TMF model to a continuous one, in order to describe the memberships of each pixel to different classes. A fuzzy energy function is constructed to describe the joint prior distribution of the fuzzy label field and the auxiliary field. The construction of fuzzy energy function also takes into account four direction information and degree of difference between neighbouring pixels. Iterative conditional estimation method and maximum posterior mode criterion are applied to implement parameter estimation and segmentation. Experimental results on simulated data and real SAR images demonstrate the effectiveness of the proposed algorithm.
Multi‐model direct generalised predictive control for automatic train operation system
Authors: Wen Shuhuan , Yang Jingwei , Rad Ahmad B. , Hao Pengcheng
Published: July 2014

The authors propose a novel multi‐model direct generalised predictive control based on predictive function control (PFC) algorithm for automatic train operation system. The proposed method facilitates autonomous driving of a train through a given guidance trajectory. Firstly, they present a multi‐model architecture based on fuzzy c‐means clustering algorithm. In order to obtain the optimal number of sub‐linear models, they apply Xie–Beni cluster validity index. In this regards, the multi‐model set is established off‐line. Secondly, the proper sub‐linear model is selected as the predictive model by using switching performance index at each time slot. The control variables are calculated by direct generalised predictive controller based on PFC. The control algorithm is simple, and can reduce the on‐line computation time by directly identifies the unknown parameters in the controller. It can avoid recursively solving the Diophantine equations. The calculation of compensation value becomes simple by introducing PFC. Finally, simulation results are provided to show the effectiveness of the proposed scheme.
Short‐term forecasting of available parking space using wavelet neural network model
Authors: Ji Yanjie , Tang Dounan , Blythe Phil , Guo Weihong , Wang Wei
Published: July 2014

The technique to forecast available parking spaces (APSs) is the foundation theory of parking guidance information systems (PGISs). This study utilises data collected on parking availability at several off‐street parking garages in Newcastle upon Tyne, England, to investigate the changing characteristics of APS. Using these baseline data the research reported here aims to build up a short‐term APS forecasting model and applies the wavelet neural network (WNN) method to the PGIS problem. After selecting optimal preferences, including training set size, delay time and embedding dimension, the APS short‐term forecasting model based on WNN is built and tested using the real‐world dataset. By experimental tests conducted using the same dataset, WNN's prediction performance is compared with the largest Lyapunov exponents (LEs) method in the aspects of accuracy, efficiency and robustness. It is found that WNN prevails through a more efficient structure and employs, barely half of the computational cost compared to the largest LEs method, which could be significant if applied to real‐time operation. Moreover, WNN enjoys a more accurate performance, for its prediction average mean square error (MSE) is 6.4 ± 3.1 (in a parking building with 492 parking lots) for workdays and 8.5 ± 6.2 for weekends, compared to the MSE of largest LEs method, 18.7 and 29.0, respectively.
Generalised asymptotic boundary conditions and their application to composite right/left‐handed rectangular waveguide with double‐ridge corrugations
Authors: Kord Ahmed M. , Eshrah Islam A.
Published: July 2014

A generalised form of the asymptotic corrugation boundary conditions (ACBCs) is presented and employed to analyse a composite right/left‐handed rectangular waveguide loaded with double‐ridge stubs. Enforcing the ACBCs yields the dispersion relation as well as the field distribution in the main waveguide without the need for any sophisticated modal analysis. The asymptotic solution proves to provide accurate results within a wide frequency band. The effect of the various geometrical parameters and the aspect ratios is investigated to determine the range of validity of the ACBCs. The results compared with the full‐wave simulations exhibit very good agreement.
Design and characterisation model for a linearly polarised patch array fed by serial rectangular waveguide network
Authors: Casas‐Olmedo Sergio , Masa‐Campos Jose Luis , Sánchez‐Olivares Pablo
Published: July 2014

A novel method for considering radiating structures independently to their feeding networks is presented. The integration of both parts separately designed suffers a critical misalignment with the theoretical behaviour caused by the mutual coupling effects between adjacent elements. This method analyses radiated near E‐field monitors to adjust the whole antenna after joining both independently designed parts. A linearly polarised patch array fed by a rectangular waveguide with internal coupling patches for X band (11–12 GHz) has been designed to validate the method performance. A double stacked microstrip patch structure with an integrated phase compensation microstrip line has been used as radiating element. The coupling patches inside the waveguide are connected to the external radiating patches by means of metallic probes. The presented method requires changes in the feeding structure as in the radiating elements. Several prototypes have been manufactured and measured: the feeding waveguide structure connectorised, the radiating patches connectorised, the union of both with SMA transitions and the final integration into the complete antenna. 18.5 dBi gain and 85% efficiency peak values, as well as 6% usable bandwidth have been experimentally achieved.
Reflectarray antenna based on grounded loop‐wire miniaturised‐element frequency selective surfaces
Authors: Edalati Arezou , Sarabandi Kamal
Published: July 2014

A reflectarray antenna based on a metal‐backed co‐planar loop‐wire Miniaturized Element Frequency Selective Surface (MEFSS) is presented in this paper. Since the unit cells are small compared to the wavelength, an equivalent lumped‐element model can describe the spectral behaviour of the proposed MEFSS structure. It is shown that the proposed unit cell provides a wider and gentler phase variation as a function of the loop size compared to a metallic patch or loop element and that the phase response of the loop‐wire element has very low sensitivity to the angle of incidence. In addition, the response of the unit cell, to a great extent, depends on the geometric and electrical parameters of the cells themselves with minimum dependency on the neighbouring elements and therefore the reflected signal phase can be controlled locally. Three samples of the proposed MEFSS structure, each giving different reflection phase values, are fabricated and measured to validate the circuit model and the design procedure. A prototype MEFSS‐based reflectarray antenna at X‐band is fabricated and measured. The prototype (260 mm × 260 mm and F/D = 1.02) shows a maximum gain of 26.3 dBi with a 1 dB‐gain bandwidth of 17% and 3‐dB beamwidth of 6° in agreement with the design parameters.
Robust, electrically small, circular inverted‐F antenna for energy‐efficient wireless microsensors
Authors: Kakoyiannis Constantine G.
Published: July 2014

The size of wireless microsensors is fundamentally limited by the bulk of the antenna and the energy pool; total energy efficiency and battery size are determined by total antenna efficiency. A printed circular inverted‐F antenna (CIFA) is mirrored against a small, crescent‐like ground plane (GNDP). The CIFA is printed on a discoid substrate that conforms to the element, the GNDP and the circumscribing sphere. It is an electrically small element designed with only three parameters: two angles and a radius. The CIFA‐plus‐GNDP radiator is resonant and matched at 2.5 GHz, where numerical results indicate that it achieves a 3.4% fractional bandwidth (FBW) combined with over 90% of efficiency, exhibits a near‐isotropic gain pattern (8 dB deviation), and approaches Thal's limit on minimum Q‐factor within 43%. The prototype CIFA achieves the required half‐radian size while scoring FBW = 3.1% (55% deviation from minimum Q) and 89.5–91.5% efficiency. Two problems pertinent to the design of small antennas for miniature portable devices are also discussed. First, an upper bound on achievable directivity is proposed, which facilitates quick assessment of antenna feasibility as a function of specified electrical size. Then, a forecast model for the prediction of minimum required operating frequency is developed based on the properties of the equivalent circuit at antenna input.
On‐chip miniaturised wideband rat‐race coupler using integrated passive device technology
Authors: Tseng Ying‐Cheng , Ma Tzyh‐Ghuang
Published: July 2014

In this study, a miniaturised wideband rat‐race coupler using glass integrated passive device (GIPD) technology is studied. The circuit miniaturisation is achieved using slow‐wave synthesised coplanar waveguides (CPWs). For wideband operation, a compact CPW phase inverter is developed and integrated. At the centre frequency, 12 GHz, the proposed rat‐race coupler is only 6.5% the size of a conventional 1.5‐λg ring coupler with the same GIPD technology; the fractional bandwidths, on the other hand, reach 65 and 32%, respectively, at the sum and difference ports. The coupler shows good amplitude and phase balances, with the transmission loss around 0.7–1.1 dB at the centre frequency.
Overlapped subarray decomposition method for an effective simulation of electrically large planar arrays of antennas
Authors: Chou Hsi‐Tseng , Lu Kung‐Yu , Chen Yu‐Chia
Published: July 2014

This study presents an overlapped subarray decomposition method to effectively simulate electrically large planar array of antennas, where the extracted subarrays can be simulated in parallel by commercial codes in a distributed fashion. This method is relatively simple and allows one to obtain a reasonable result within the acceptable level of accuracy for the engineering purpose. A plug‐in code can be built up by using a commercial code as a computational engine. The characteristics of this method are investigated by considering the simulation of a dipole antenna array via the application of the method of moments (MoM). It is also validated by performing a realistic design of microstrip patch antennas. The comparisons with measurement results are performed and summarised.
Slot combined complementary split ring resonators for mutual coupling suppression in microstrip phased arrays
Authors: Qamar Zeeshan , Riaz Laeeq , Chongcheawchamnan Mitchai , Khan Shahid A. , Shafique Muhammad Farhan
Published: July 2014

This study presents a tailored metamaterial structure for mutual coupling suppression in the E coupled microstrip phased arrays. Configured slot combined complementary split ring resonator (SCCSRR) is proposed for decoupling. A detailed analysis of the suppression characteristics of SCCSRR is presented along with its design methodology and parametric analysis. The SCCSRR pairs have been integrated with the microstrip phased array on surface and in the ground plane without any added fabrication complexity. The proposed design offers additional coupling suppression of 19 dB as compared with non‐decoupled array of same dimension. The coupling suppression of −42 dB for 3.7 GHz array has been achieved successfully. The element separation is kept at 0.5 λo and the complete design with two radiating elements measures 84 × 44 mm2.
Single‐pin, single‐layer, dual‐band patch antenna for global positioning system and satellite digital audio radio system automotive applications
Authors: Ghafari Elias , Aloi Daniel N.
Published: July 2014

A low‐cost, reduced‐size, single‐feed, single‐layer microstrip patch antenna is presented that receives right‐hand circularly polarised satellite signals for the global positioning system's L1‐Band (1575.42 MHz) and left‐hand circularly polarised satellite signals and vertically linearly polarised terrestrial signals for the satellite digital audio radio system band (2320–2345 MHz). The proposed antenna is constructed of a main central patch and a ring surrounding it, both with truncated corners to achieve the desired circular polarisation characteristics. The two patches are connected to each other using four long and thin microstrip transmission lines. The design, simulation and measured results are presented. The effects of varying key antenna physical parameters were carefully examined and discussed in detail to characterise their effects on operational bandwidth.
Tunable millimetre‐wave phase shifting surfaces using piezoelectric actuators
Authors: Mavridou Marina , Feresidis Alex P. , Gardner Peter , Hall Peter S.
Published: July 2014

A novel technique for tuning periodic phase shifting surfaces at millimetre‐waves is presented. The proposed structure consists of a periodic surface placed over a ground plane creating an air cavity. The periodic surface is formed by a two‐dimensional array of metallic square loop elements printed on a 0.8 mm thick dielectric substrate. When excited by a plane wave, the structure is acting as an artificial impedance surface, reflecting the incident wave with a wide range of phase values within a specific frequency band. The tuning is achieved by means of a small number of piezoelectric actuators which support the periodic surface. The actuators are placed around the periodic surfaces thereby not interfering with the radiation performance and introducing no losses. They produce a displacement between the periodic surface and the ground plane when voltage is applied, which in turn changes the reflection phase response of the structure. Full wave periodic simulations have been carried out in three‐dimensional electromagnetic simulation software (CST Microwave StudioTM) to extract the reflection characteristics and evaluate the expected tuning range of the proposed structure. A prototype has been fabricated and measured validating the concept.
Wideband balanced out‐of‐phase network based on double‐sided parallel‐strip line
Authors: Chang Yumei , Che Wenquan , Wang Xiyao
Published: July 2014

A new wideband out‐of‐phase balanced power dividing/combining network is proposed in this study. Large bandwidth for the differential mode with broadband common mode suppression can be easily realised. Out‐of‐phase power division can be also achieved for Ports 2, 3 (Port 2′, 3′) by the double‐sided parallel‐strip line 180° swap. A planar wideband balanced out‐of‐phase network with bandwidth of 33% for the differential mode with wideband common mode suppression is designed and fabricated for demonstration. Good agreement is observed between simulated and measured performances, indicating the validity of the proposed design strategies.
Substrate integrated waveguide antenna subarray for broadband circularly polarised radiation
Authors: Djerafi Tarek , Youzkatli‐el‐Khatib Bassel , Wu Ke , Tatu Serioja‐Ovidiu
Published: July 2014

This study presents a compact circularly polarised array using tapered slot antenna fed by a substrate integrated waveguide (SIW) power divider. With the proposed topology, broadband circularly polarised property is achieved and total gain can be increased by controlling the element length, conserving the same footprint area. The different 2 × 2 cell configurations are investigated. Simple and integrated series–parallel SIW feed for the choose cell is presented. A 2 × 2 antenna array is designed and fabricated using SIW E‐plane power divider. The measured 10 dB return loss and 3 dB axial ratio bandwidths are 35.65 and 32.3%, respectively. The measured antenna gain is 14.4 dBi at 35 GHz.
Equal‐gain combining reception over Gamma–Gamma turbulence channels with pointing errors
Authors: Samimi Hossein
Published: July 2014

In this study, we investigate the performance of free‐space optical communication system employing equal‐gain combining receiver and operating over Gamma–Gamma turbulence channel with pointing errors. We derive the Bealieu series for the cumulative distribution function (CDF) and the probability density function (PDF) of the output signal‐to‐noise ratio (SNR), which is a function of the sum of the received irradiance of the individual receiver branches. We derive exact closed‐form expressions for the coefficients of the Bealieu series, which makes it possible to compute the CDF and the PDF of the output SNR for different channel conditions and for arbitrary values of diversity order. To give an example of the application of the derived analytical results, the outage performance of the considered system is investigated and the effects of the pointing error are studied. Numerically evaluated and computer simulation results are given that verify the accuracy of the proposed mathematical framework.
13.625 Gb/s real‐time dual‐band adaptive optical orthogonal frequency division multiplexing transmissions over 25 km standard single‐mode fibre intensity modulation and direct detection systems utilising strongly saturated reflective semiconductor optical amplifier intensity modulators
Authors: Zhang Qianwu , Hugues‐Salas Emilio , Giddings Roger P. , Zhang Junjie , Wang Min , Tang Jianming
Published: July 2014

Record‐high 13.625 Gb/s real‐time end‐to‐end dual‐band optical orthogonal frequency division multiplexing (OFDM) transmissions are experimentally demonstrated over intensity modulation and direct detection‐based 25 km standard single‐mode fibres utilising 1.125 GHz reflective semiconductor optical amplifier (RSOA) intensity modulators. The 7.375 Gb/s OFDM baseband (0–2 GHz) and 6.25 Gb/s OFDM passband (4.125–8.125 GHz) are adaptively modulated independently and sampled at 4 GS/s. Experimental results show that strongly saturated RSOAs can intensity‐modulate adaptive bit‐ and power‐loaded radio frequency (RF) OFDM signals having bandwidths approximately eight times higher than the 3 dB small‐signal modulation bandwidths of the RSOAs.
Analysis, design and performance of a zero‐current‐switching pulse‐width‐modulation interleaved boost dc/dc converter
Authors: Wang Chien‐Ming , Lin Chang‐Hua , Hsu Shih‐Yung , Lu Chien‐Min , Li Jyun‐Che
Published: July 2014

A novel interleaved boost dc/dc converter with zero‐current‐switching pulse‐width‐modulation (ZCS‐PWM) characteristic using a simple ZCS‐PWM auxiliary circuit is presented in this paper. The proposed converter combines the conventional PWM technique and ZCS technique to promote the circuit performance. The proposed converter uses dual boost converters which are operated at interleaved mode to increase the output power level. Thus, the proposed converter does not only decreases the current stress on main circuit devices but reduces the input ripple current and output capacitor size. Because the proposed converter establishes a common ZCS‐PWM auxiliary circuit on used dual boost converters, it can greatly reduce the size and cost. And, it can provide the ZCS characteristic on main switches and auxiliary switches with a wide range of load to improve the problem of switching losses and EMI. Thus, its topology is simple and compact. Besides operating at constant frequency and reducing commutation losses, the proposed converter has no additional current stress and conduction loss in the main switch compared with the conventional interleaved boost dc/dc converter. The principle of operation, theoretical analysis and experimental results of the proposed boost converter, rated 1 kW and operating at 40 kHz, are provided in this paper to verify the performance of this new family of converters.
Field‐programmable gate array‐based linear–non‐linear control with high‐resolution digital pulse width modulator and high‐speed embedded analogue‐to‐digital converter for multi‐phase voltage regulator modules
Authors: Sanz Marina , Quintero Jesús , Barrado Andrés , Fernández Cristina , Zumel Pablo , Lázaro Antonio
Published: July 2014

Power converters for applications with high switching frequency and tight output voltage regulation such as voltage regulator modules (VRM) for microprocessors power supplies require fast dynamic response to meet the specifications. An existing control technique known as linear–non‐linear (LnL) control strategy allows improving the transient converter response by means of an easy rule for the saturation of the duty cycle. The use of a digital implementation can optimise the transient response of the multi‐phase VRM with LnL. However, digital control leads to other problems derived from time discretisation and finite word length effects. The limited resolution and the sampling delay are critical issues for digital control implementation of multi‐phase VRM with LnL control. As a result, a high‐resolution digital pulse width modulator (DPWM) and high‐speed analogue‐to‐digital (A/D) converter are required to obtain proper performance of the converter. This study is focused on the digital implementation of the well‐known LnL control in a multi‐phase VRM taking advantage of low‐cost field‐programmable gate array resources. A detailed description of the digital implementation of the main converter control blocks, which are the A/D converter, the compensator and the DPWM, is provided in the paper.
Fast factorised backprojection algorithm in elliptical polar coordinate for one‐stationary bistatic very high frequency/ultrahigh frequency ultra‐wideband synthetic aperture radar with arbitrary motion
Authors: Xie Hongtu , An Daoxiang , Huang Xiaotao , Li Xiangyang , Zhou Zhimin
Published: July 2014

The precise disposal of azimuth variance of range cell migrations and motion errors in the one‐stationary bistatic very high frequency/ultrahigh frequency ultra‐wideband synthetic aperture radar imaging is a real challenge for efficient frequency‐domain algorithms, but can be precisely managed by time‐domain approaches. In this study, a novel bistatic fast factorised backprojection (BFFBP) algorithm is presented, which can deal with these two effects accurately and achieve the computational performance in parity with frequency‐domain algorithms. First, the imaging geometry with arbitrary motion in elliptical polar coordinate is provided, and the analytical expression of the bistatic backprojection algorithm in this coordinate system is derived, which provides a theory basis for the proposed algorithm. Then, based on the subaperture imaging geometry, the sampling requirements considering motion errors is deduced, which offers the optimal tradeoff between the imaging quality and computational speed. The advantage of using elliptical polar coordinate system for implementing the BFFBP algorithm is analysed. Finally, the implementation and computational burden of the BFFBP algorithm are discussed. Simulation results are shown to prove the correctness of the theory analysis and validity of the proposed approach.
Improved method for synthetic aperture radar scattered wave deception jamming
Authors: Zhao Bo , Zhou Feng , Tao Mingliang , Zhang Zijing , Bao Zheng
Published: July 2014

This study presents an improved scattered wave jamming method for synthetic aperture radar (SAR). The jammer adjusts the time‐delay and the phase of the intercepted SAR signal. Then, a false scene is created to provide an effective protection for a certain area. It requires a lower jamming power than barrage jamming and has less computational complexity than direct‐path deception jamming. Based on the performance analysis of scattered wave jamming, pulse repetition intervals to delay retransmission, and a modulation centre shift are proposed as improvements to enlarge the jamming area.
Modelling of ionospheric time delay of Global Positioning System (GPS) signals using Taylor series expansion for GPS Aided Geo Augmented Navigation applications
Authors: Naveen Kumar Perumalla , Sarma Achanta D. , Supraja Reddy Ammana
Published: July 2014

The positional accuracy of Indian Global Positioning System Aided Geo Augmented Navigation (GAGAN) system is affected by many errors and among them the ionospheric time delay error is the predominant error. The Indian ionosphere is characterised by large gradients, intense irregularities and equatorial anomaly conditions and hence suitable ionospheric model is necessary for GAGAN. Compared with global and regional ionospheric models, not much significant work is reported on local ionospheric models for Indian region. In this study, using Indian Satellite Based Augmentation System data, a local ionospheric model based on Taylor series expansion (TSE) is used. Initially, a network of 17 GAGAN total electron content stations data are considered in the analysis for both quiet and disturbed days. The ionospheric time delay results of the TSE model indicate that the model is performing better for quiet days than the disturbed days. The delay because of the TSE model is compared with that of the delays because of Klobuchar and IRI‐2007 models and experimental GAGAN data. The obtained results shows that the TSE model is estimating delay more closely with respect to GAGAN data than that of the Klobuchar and IRI‐2007 models and may be considered for use in offline applications.
Intelligent stochastic framework to solve the reconfiguration problem from the reliability view
Authors: Kavousi‐Fard Abdollah , Niknam Taher , Khooban Mohammad Hassan
Published: July 2014

This study proposes a new method to employ the distribution feeder reconfiguration as a reinforcement strategy to enhance the reliability of the distribution systems. Also, several wind power sources are considered to assess their effects on the reliability indices. In order to make the final results more dependable, a stochastic framework based on the probabilistic power flow is utilised to consider the uncertainty of forecast/measurement error of the active and reactive loads, failure rate, repair rate and output generation of wind units, concurrently. The objective functions to be investigated are (i) system average interruption frequency index, (ii) average energy not supplied, (iii) active power losses and (iv) total cost. Moreover, a new modified optimisation method based on harmony search algorithm is proposed to improve the total ability of the algorithm to explore the problem search space globally. The effectiveness and efficiency of the proposed method are examined through two radial distribution test systems.
Two‐dimensional modelling of dielectric barrier discharges using charge simulation technique‐theory against experiment
Authors: Wedaa Hassan , Abdel‐salam Mazen , Ahmed Adel , Mizuno Akira
Published: July 2014

This study is aimed at calculating the discharge onset voltages and power loss of the AC discharge using the charge simulation technique in a wire‐cylinder reactor with a dielectric barrier at atmospheric pressure and room temperature. The calculation of the discharge onset voltages is based on the criterion of self‐sustained growth of onset streamers and Trichel pulses in positive and negative half cycles, respectively. The emission of ions (space charges) from the wire surface is assumed to take place when the magnitude of the surface charge exceeds the corresponding onset values based on pre‐defined discharge onset voltages for both positive and negative half cycles. The space charges are displaced by the prevailing electric field until accumulated on the glass surface. Discharge power loss corresponds to the energy required for the displacements of emitted space charges. The calculated values of the discharge onset voltage and power loss agreed reasonably with those measured experimentally.