bluuebunny/crossref_metadata_2025 huggingface dataset:
Electromagnetic modelling of surfaces using method of moments with calculated phase mesh
Authors: Sawitzki Axel
Published: August 2015

An alternative method of moments (MoM) solution for the radiation and scattering of surfaces is presented. One limit of MoM is the high number of basis functions needed, for the segmentation of electrically large surfaces. In this study, a conventional MoM solution is defined with quadrilateral surface patches and at least eight rooftop basis functions per wavelength. Galerkin testing is applied. This conventional MoM is extended with a new approach for the surface segmentation, called the calculated phase mesh (CPM). Efficient basis functions are chosen, and their positions on the surface are calculated with the incident field. In the theory part, the number of unknowns for scatterers with electrically large dimensions is reduced by 50%, compared with conventional MoM meshes with eight functions per wavelength. The incident field on surfaces is calculated numerically. This allows the application of CPM on scattering bodies with a variety of field sources, for example, both the near and the far field of antennas. The valid frequency range for the meshes is described. Three numerical examples are presented. In one example, the number of basis functions was reduced to 69.3%, compared with conventional MoM. The third example shows the application on three‐dimensional scattering bodies.
Mechanically pattern reconfigurable antenna using metasurface
Authors: Zhu Hai Liang , Cheung Sing Wai , Yuk Tong Ip
Published: August 2015

A radiation pattern reconfigurable antenna designed using metasurface (MS) is proposed in this study. The pattern reconfigurable metasurfaced (PaRMS) antenna is composed of a planar semi‐circular MS placed directly atop of a planar circular patch antenna with a diameter of 70 mm (1.2λ0), making it compact and low profile. The main‐beam direction of the antenna has an angle of 32° from the boresight direction. By rotating the MS around the centre of the patch antenna, the antenna beam can be steered continuously. The PaRMS antenna is studied and designed to operate at around 5.5 GHz. To verify the results of simulation, the PaRMS antenna is fabricated and measured. Results show that the antenna has an operating bandwidth from 5.4 to 5.6 GHz and measured peak realised gain of 7.2 dBi.
Dispersion analysis of a fishnet metamaterial based on the rotated transmission‐line matrix method
Authors: Xiong Ying , Russer Johannes A. , Che Wenquan , Shen Guangxu , Han Ye , Russer Peter
Published: August 2015

A novel three‐dimensional (3D) lumped circuit‐based metamaterial topology to model a 2D fishnet structure is proposed. The rotated transmission‐line matrix (RTLM) unit cell, obtained as one independent half cell from the typical TLM unit cell by rotating the polarisations on each TLM unit port by 45°, saves computation time and decreases the cost in processing data when a structure is analysed, especially when some specific components of the structure are processed. Here, an RTLM unit cell is used to construct the lumped circuit of a fishnet structure. The dispersion characteristics of the lumped fishnet circuit are obtained and used to analyse the eigenmode and the propagation coefficient and Bloch impedance are investigated to explain the frequency characteristics. At the frequency region considered, the same left‐handed frequency behaviour of the lumped fishnet circuit is achieved by the proposed compact fishnet RTLM model, agreeing well with the simulation results.
Tunable band‐pass filter with wide stopband and high selectivity using centre‐loaded coupled structure
Authors: Zhu He , Abbosh Amin
Published: August 2015

A tunable band‐pass filter using a coupled structure that is centrally tapped with a resonator is proposed for wideband applications. The utilised resonator includes parallel‐coupled lines loaded with a short‐ended varactor. The resonator enables the independent tunability of two transmission zeroes (TZs), which define the passband of the filter. Moreover, the structure creates multiple TZs in upper stopband which enable realising a wide spurious‐free stopband. A thorough theoretical analysis is used to verify the performance and calculate the initial design parameters. To validate the proposed design procedure, a prototype is designed, fabricated and tested. The simulated and measured results agree with the derived theory, and indicate a tuning range for the 3 dB bandwidth from 47.8 to 105.7% with <1.4 dB of insertion loss and more than 12 dB of return loss. It also has more than 18 dB of attenuation across a stopband extending to around four times the centre frequency.
Predicting total tropospheric attenuation on monthly basis
Authors: Luini Lorenzo , Capsoni Carlo , Riva Carlo , Emiliani Luis David
Published: August 2015

This contribution presents a comprehensive methodology for the global prediction of monthly total tropospheric attenuation statistics. This goal is achieved by combining the outputs of physically‐based models for the estimation of the attenuation induced by each relevant atmospheric constituent (gases, clouds and rain). To evaluate the model's accuracy, worst month total attenuation statistics are first derived from the monthly attenuation predictions, and tests are performed against the measurements included in the global DBSG3 database of International Telecommunication Union‐Radiocommunication Sector. Results show a good prediction accuracy, which corroborates the use of the proposed physical model to aid engineers in planning future high‐frequency satellite communication systems on the basis of the worst month concept.
Resonator switching techniques for notched ultra‐wideband antenna in wireless applications
Authors: Abdalla Mahmoud Abdelrahman , Ibrahim Ahmed A. , Boutejdar Ahmed
Published: August 2015

This study presents the design of switching techniques for dual‐notched ultra‐wideband antenna. The dual band‐notched frequencies are achieved by using switched defected microstrip structure band stop filter inserted in the microstrip feed line and a switched meandered slot etched in the radiation patch. The switching reconfiguration is accomplished by combining the two ideal switches to introduce a notch filter response to prevent the interference to the primary users operating in the middle and upper WiMAX wireless local area network bands. The proposed structure has four modes by controlling the two switches on and off. The proposed antenna has good matched impedance from 2.5 to 12 GHz with two notched bands from 3.3 to 3.8 GHz (middle WiMAX applications) and from 5.1 to 5.9 GHz (upper WiMAX applications). The antenna is fabricated and tested. Good agreement is achieved between the simulated and measured results.
Polarisation diverse multiple input–multiple output antenna with enhanced isolation
Authors: Sarma Aswathy K. , Arun Henridass , Kanagasabai Malathi , Velan Sangeetha , Raviteja Chinnambeti , Alsath M. Gulam Nabi
Published: August 2015

In this article, two‐element monopole multiple input–multiple output (MIMO) antenna with polarisation diversity for 4G and other applications has been presented. The designed antenna covers 16% (1701–2001 MHz) of bandwidth around the design frequency (1850 MHz) which includes both DCS‐1800 and DCS‐1900 bands. The two antennas are placed orthogonally and symmetrically with edge‐to‐edge spacing of 5.5 mm (λ0/30). With the placement of interconnected swastika‐shaped resonator between the two monopole antennas, there is an isolation enhancement of 60 dB thus reducing the envelope correlation coefficient value ranging from 0.016 to 6.12 × 10−10 and improving the diversity gain ranging from 9.9 to 10 dB within the −10 dB bandwidth. A prototype has been fabricated and validated using measurements.
Millimetre wavelength variable focusing antenna for power beaming and active denial systems
Authors: Danieli Erez , Abramovich Amir , Pinhasi Yosef
Published: August 2015

A design of a millimetre wavelength antenna with adjustable focal length is demonstrated in this study. This antenna is designed to operate in the near field regime, and has the ability to change the focal plane position. The structure of the antenna is based on a Cassegrain configuration in order to deliver maximum power density to a pre‐defined focal plane. Possible applications are radioactive power beaming and active denial systems. The analysis and development of this antenna were carried‐out using the Gaussian beam model and the ABCD matrix method in order to find the focus position and spot size as a function of the axial distance. The development of the quasi‐optical components of the Cassegrain antenna, simulation results and experimental results are described in this work.
Large‐signal analytical approach to a disc‐loaded gyro‐TWT amplifier
Authors: Singh Rajiv Kumar
Published: August 2015

In the present study, large‐signal analysis of a disc‐loaded gyro‐travelling wave tube amplifier has been presented. For this purpose, analytical theory for non‐linear analysis of an arbitrary‐shaped interaction structure has been extended for a disc‐loaded interaction structure. Power profile results of the present theory, taking waveguide disc‐hole radius equal to waveguide‐wall radius where the structure becomes a smooth wall circular waveguide, closely matches with the published results of a circular waveguide. Comparison of already published small‐signal theory results and the present large‐signal theory has been done and a fair agreement (within 4%) has been achieved. Spatial power and efficiency profile for a disc‐loaded gyro‐traveling wave tube with structure parameters rD/rW = 0.6, L/rW = 0.4 and T/rW = 0.1 operating in TE02‐mode at 91.4 GHz has been presented.
Analysis and synthesis of supershaped dielectric lens antennas
Authors: Bia Pietro , Caratelli Diego , Mescia Luciano , Gielis Johan
Published: August 2015

A novel class of supershaped dielectric lens antennas, whose geometry is described by the three‐dimensional (3D) Gielis’ formula, is introduced and analysed. To this end, a hybrid modelling approach based on geometrical and physical optics is adopted in order to efficiently analyse the multiple wave reflections occurring within the lens and to evaluate the relevant impact on the radiation properties of the antenna under analysis. The developed modelling procedure has been validated by comparison with numerical results already reported in the literature and, afterwards, applied to the electromagnetic characterisation of Gielis’ dielectric lens antennas with shaped radiation pattern. Furthermore, a dedicated optimisation algorithm based on quantum particle swarm optimisation has been developed for the synthesis of 3D supershaped lens antennas with single feed, as well as with beamforming capabilities.
Compact printed ultra‐wideband diversity monopole antenna with slant inverted tree‐shaped stub
Authors: Kumar Raj , Pazare Neha
Published: August 2015

A compact two‐port diversity antenna is proposed and experimentally investigated. One of the ports is connected to a microstrip feed, whereas the other port to a coplanar waveguide feed. The radiating elements are semi‐circular disc‐shaped monopoles rotated around their centres. By shaping the common ground plane, ultra‐wide impedance bandwidth is achieved. The measured bandwidths are 2–12 GHz at port 1 and 2.3–10.2 GHz at port 2. To obtain good isolation between the ports, a slant inverted tree‐shaped structure is attached at the corner of the ground plane. The measured isolation is about 20 dB throughout the band. The antenna has omni‐directional radiation patterns with a moderate peak gain of 2–7 dBi. To evaluate the diversity performance, the envelope correlation coefficient, diversity gain and capacity loss are calculated. A modified design with impedance bandwidth at port 2 extending beyond 11 GHz is also presented. The proposed diversity antenna is an attractive candidate to provide polarisation diversity and enhance channel capacity in a rich scattering environment.
Bandwidth and radiation specifications enhancement of monopole antennas loaded with split ring resonators
Authors: Alibakhshi‐Kenari Mohammad , Naser‐Moghadasi Mohammad , Sadeghzadeh R.A.
Published: August 2015

New broadband antennas loaded with split ring resonators (SRR) are proposed and investigated. The results illustrate that by loading the conventional monopole antennas with an asymmetrical meander lines SRR, a lower resonance frequency mode can be excited. The dimensions of the SRR have been selected to provide a resonance close the resonance of the monopole antennas. The results illustrate that when both resonance coincide the antennas bandwidths and radiation properties can be enhanced. The length and width of the antennas are 25 × 10−2λ0 × 11 × 10−2λ0 and 25 × 10−2λ0 × 21 × 10−2λ0 at 4 GHz for monopole antennas, and 29 × 10−2λ0 × 21 × 10−2λ0 at 2.9 GHz for both monopole antennas loaded with SRR. For antennas without SRR loading, maximum of measured gains and efficiencies are 3.6 dBi and 78.5% for F‐antenna, and 3.9 dBi and 80.2% for T‐antenna, hence they appear at 5 GHz. For antennas with SRR loading, these parameters are 4 dBi and 81.2% for F‐antenna, and 4.4 dBi and ∼83% for T‐antenna, which appeared at 6 GHz. By implementing the meander lines SRR as a matching load on the monopole antennas, the resulted antennas cover the measured frequency bandwidths of 2.9–6.41 GHz and 2.6–6.6 GHz (75.4 and ∼87% fractional bandwidths), which are ∼2.4 and 2.11 times more than monopole antennas with an approximately same in size.
Four‐element quad‐band multiple‐input–multiple‐output antenna employing split‐ring resonator and inter‐digital capacitor
Authors: Sarkar Debdeep , Singh Aditya , Saurav Kushmanda , Srivastava Kumar Vaibhav
Published: August 2015

In this study, a novel four‐element multiple‐input–multiple‐output (MIMO) antenna having quad‐band characteristics is proposed. A coplanar waveguide‐fed monopole is loaded with a split‐ring resonator and an inter‐digital capacitor to achieve miniaturisation and quad‐band operation. These quad‐band elements are arranged properly to implement a four‐element MIMO configuration which provides both spatial and pattern diversities. The achieved isolation performance is better than 20 dB. Measurement results confirm that the proposed MIMO antenna operates at 1.95, 2.39, 2.64 and 3.27 GHz with impedance bandwidths of 2.66, 6.57, 8.8 and 4.09%, respectively. The proposed antenna exhibits quasi‐monopolar radiation pattern and measured envelope correlation coefficient <0.01 is obtained in all the operating bands. The proposed antenna can be useful for MIMO applications in global system of mobile/Bluetooth/wireless local area network/worldwide interoperability for microwave access operating bands.
Impact of the antenna directivity on path loss for different propagation environments
Authors: Azevedo Joaquim Amandio , Santos Filipe Edgar , Sousa Tony Andres , Agrela Jenny Manuela
Published: August 2015

Log‐normal is a very common propagation model used to estimate the path loss introduced by a given environment. However, in most cases the parameters of the model are antenna specific. In this work, it is shown that the path loss exponent is highly dependent on the antenna pair used in the communication system. Large errors are introduced in the prediction of the path loss if the antennas are different from those used to obtain the parameters of the propagation model. An improved model is developed for the 2.4 GHz industrial, scientific and medical band to estimate the path loss exponent for different antenna directivities knowing the path loss exponent of a reference antenna. The model uses the antenna beamwidth and the antenna gain to obtain a parameter related to the path loss.
Frequency reconfigurable antenna for hand‐held wireless devices
Authors: Bhellar Benazeer , Tahir Farooq A.
Published: August 2015

In this communication, a balanced frequency‐reconfigurable antenna for nine‐band operation covering GSM 850/900/1800/1900/UMTS2100/LTE700/2300/2500 /WLAN2400 bands for multiradio mobile platforms is presented. The antenna consists of simple planar geometry with size of 60 × 15 mm2 that is quite practical for implementation on current consumer‐type multiradio mobile platforms. The design comprises of a feeding strip and an electromagnetically coupled parasitic shorted strip whose effective length is electronically controlled through a single PIN diode. By combining both ON and OFF states of the PIN diode, four resonance modes are achieved covering nine bands of LTE/WWAN/WLAN operation. The proposed antenna is successfully simulated, fabricated and measured. It has excellent radiation efficiency and positive gains over all nine bands of operation.
Balanced dual‐segment cylindrical dielectric resonator antennas for ultra‐wideband applications
Authors: Majeed Asmaa H. , Abdullah Abdulkareem S. , Sayidmarie Khalil Hassan , Abd‐Alhameed Raed A. , Elmegri Fauzi , Noras James M.
Published: August 2015

This study reports on balanced dual‐segment cylindrical dielectric antennas with ultra‐wideband (UWB) operation. A T‐shaped slot and L‐shaped microstrip feeding line was suggested to furnish a balanced coupling mechanism for feeding two DRAs, and then the performance of the proposed antenna was analysed and optimised against the target frequency band. The proposed antenna was then modified by adding a C‐shaped strip to increase the gain. The performances of both balanced antennas were characterised and optimised in terms of antenna reflection coefficient, radiation pattern, and gain. The antennas cover the frequency range from 6.4 to 11.736 GHz, which is 58.7% bandwidth. A maximum gain of 2.66 dB was achieved at a frequency of 7 GHz with the first antenna, with a further 2.25 dB increase in maximum gain attained by adding the C‐shaped strip. For validation, prototypes of the two antennas were fabricated and tested. The predicted and measured results showed reasonable agreement and the results confirmed good impedance bandwidth characteristics for UWB operation from both proposed balanced antennas.
Transmission of the maximum number of signals through a multiconductor transmission line without crosstalk or return loss: theory and simulation
Authors: Vulfin Vladimir , Ianconescu Reuven
Published: August 2015

Multiconductor communication is widely used in electronic applications for fast data transfer between different devices. The most common multiconductor transmission media are Cat 6 Ethernet cables, flat cables, and backplanes. In all applications, the data is transferred differentially between pairs of conductors, so that roughly the number of transmitted signals is half the number of conductors. Physically, between N + 1 conductors it is possible to transmit N signals and the reason for not doing so is the huge crosstalk and return loss that would arise when transmitting so many signals. The current work suggests an algorithm for transmitting the maximum number of possible signals without crosstalk or return loss.
Input impedance and radiation pattern of a resonant dipole embedded in a two‐dimensional periodic leaky‐wave structure
Authors: Bakhtafrouz Ahmad , Borji Amir
Published: August 2015

Array scanning method (ASM) is employed to study the input impedance and radiation pattern of a two‐dimensional periodic leaky‐wave antenna (LWA). The antenna consists of a narrow horizontal strip dipole of arbitrary length underneath a two‐dimensional (2D) periodic screen of metallic patches, which acts as a partially reflective surface (PRS), and backed by a ground plane. First, the Green's function in the presence of the 2D array of metallic patches is calculated by means of the ASM and then the current distribution and input impedance of the source dipole are calculated through the electric field integral equation and method of moments. The far‐field pattern is computed using the reciprocity theorem. Compared to the Hertzian dipole, which is the only type of source that has been considered in the literature, the resonant dipole substantially improves the performance of periodic LWA in terms of radiated power, efficiency and bandwidth. Numerical results are given for a resonant dipole over the frequency range of 60–70 GHz and compared with those obtained from commercial softwares, FEKO® and Ansys HFSS®, showing an excellent agreement with considerable improvement in terms of memory usage and computational speed.
Evaluation of a communication‐based fault ride‐through scheme for offshore wind farms connected through high‐voltage DC links based on voltage source converter
Authors: Nanou Sotirios , Papathanassiou Stavros
Published: August 2015

Offshore wind farms connected to the mainland through high‐voltage DC links based on voltage source converters (VSC‐HVDC) are subject to grid code requirements, such as fault ride‐through (FRT) capability and dynamic voltage support. To address the challenge of FRT capability, sophisticated control strategies are required, capable of handling the power imbalance between the two interconnection ends during onshore grid faults. Τhis study proposes an FRT method which combines a de‐loading control strategy for the offshore wind turbines, utilising the communication infrastructure of the VSC‐HVDC system, with a DC chopper to dissipate the power surplus that cannot be effectively curtailed via the communication link. The impact of communication system latency on the expected FRT response and the required rating of the DC chopper is investigated using a linearised small‐signal model introduced in this study, whose results are validated against time‐domain simulations using detailed electromagnetic transient‐type models for the entire system. It is concluded that the required rating of chopper resistors can be substantially reduced when existing communication capabilities are exploited, even in the presence of relatively high communication delays.
Wind turbine reliability estimation for different assemblies and failure severity categories
Authors: Kaidis Christos , Uzunoglu Bahri , Amoiralis Filippos
Published: August 2015

This study discusses the life‐cycle analysis of wind turbines through the processing of operational data from three modern European wind farms. A methodology for supervisory control and data acquisition data processing has been developed combining previous research findings and experience from operational wind farms followed by statistical analysis of the results. The analysis was performed by dividing the wind turbine into assemblies and the failures events in severity categories. Depending on the failure severity category a different statistical methodology was applied, examining the reliability growth and the applicability of the ‘bathtub curve’ concept for wind turbine reliability analysis.
Measurement fusion using maximum‐likelihood estimation of ballistic trajectories
Authors: Janczak Dariusz , Sankowski Miroslaw , Grishin Yuri
Published: August 2015

A novel method is proposed for asynchronous measurement fusion using maximum‐likelihood (ML) estimator. This method is applied to multiple radar tracking and reconstruction of ballistic trajectories. The performance and robustness of the ML measurement fusion technique are analysed using a generic simulation scenario involving multi‐sensor weapon locating in urban environment. Accuracies of firing point and impact point estimation of mortar grenades and artillery rockets are also evaluated taking into account different radars’ characteristics and geometries of the scenario. Immunity to glint noise, limited time of observation, and uncertainty of ballistic coefficient are also investigated. This study shows the effectiveness of the new method, advantages over track fusion approach, and reveals its practical value.
Global navigation satellite system interference tracking and mitigation based on an adaptive fading Kalman filter
Authors: Kang Chang Ho , Kim Sun Young , Park Chan Gook
Published: August 2015

A time‐domain signal tracking and mitigation algorithm is proposed to estimate the frequency of interference in a global navigation satellite system (GNSS) so as to classify different types of interference and to mitigate interference. The frequency of GNSS interference can be obtained using the properties of the trigonometric functions of received signal samples, but these values contain numerous errors caused by measurement noise and frequency changes associated with the interference. To reduce these errors, an adaptive fading Kalman filter is applied in the proposed algorithm. Furthermore, a low‐pass differentiator and a pattern enhancement algorithm are used to estimate the sweep period of chirp‐type interference, which is used to reset the filter parameter for estimating the frequency of the interference accurately. By estimating the sweep period, the interference identification logic is designed to select the proper system model of the Kalman filter. Finally, in order to mitigate the interference, the denoised frequency from the filter is used to design a notch filter which eliminates the interference in the received signal. The frequency tracking performance of the proposed algorithm is verified to compare with conventional algorithms and the mitigation performance of the proposed algorithm is evaluated by means of Monte Carlo simulations.
Histogram probabilistic multi‐hypothesis tracker with colour attributes
Authors: Davey Samuel J. , Vu Han X. , Arulampalam Sanjeev , Fletcher Fiona , Lim Cheng‐Chew
Published: August 2015

The histogram probabilistic multi‐hypothesis tracking (H‐PMHT) algorithm is a multi‐target track‐before‐detect method that has been demonstrated to be scalable and efficient and shows good performance on video imagery. However, its application has been limited to intensity‐only imagery. In practice, colour and information, such as texture, are often available and can be very helpful when targets are close together. This study compares two alternative methods that incorporate colour information in the H‐PMHT: an existing method referred to as spectral H‐PMHT and a new approach that treats the colour information as attribute data. The methods are compared with intensity‐only H‐PMHT on simulations and benchmark data from the VS‐PETS03 archive.
Design and performances evaluation of new Costas‐based radar waveforms with pulse coding diversity
Authors: Touati Nadjah , Tatkeu Charles , Chonavel Thierry , Rivenq Atika
Published: August 2015

Costas codes are a variant of pulse compression waveforms, largely studied for their attractive time–frequency properties. Their ‘thumbtack‐like’ ambiguity function (AF) makes them highly suitable for delay and Doppler estimation, in radar and sonar applications. However, this behaviour depends heavily on the length of the code: the improvement in delay–Doppler resolutions and AF sidelobes level needs an increase in the size of the code. In this study, designs that allow good performance without increasing the size of the code are proposed. They are based on a modification of Costas codes by widening frequency separation between hops and replacing rectangular pulses by other waveforms. This will lead to a removal of autocorrelation function grating lobes that normally appear when frequency separation is increased. The originality of the work lies in the proposal of diversified pulse waveforms, such as phase codes, Slepian sequences, and other Costas codes, to encode main Costas pulses. A performance comparison of the proposed approaches is supplied. Such waveforms could also be of interest for applications where waveform diversity is desired.
Fractal properties of autoregressive spectrum and its application on weak target detection in sea clutter background
Authors: Fan Yifei , Luo Feng , Li Ming , Hu Chong , Chen Shuailin
Published: August 2015

This study concerns the fractal properties of sea clutter in the power spectrum domain. To overcome the deficiencies of Fourier transform analysis, the power spectrum of the sea clutter is obtained by autoregressive (AR) spectrum estimation. The AR model is a linear predictive model, which estimates the power spectrum of sea clutter form its autocorrelation matrix and has a higher frequency resolution than Fourier analysis. This study concentrates on analysing the fractal property of the power spectrum based on AR spectral estimation and its application on weak target detection. First, fractional Brownian motion is taken as an example to prove the fractal property of the power spectrum. Then, real measured X‐band data is used to verify the fractal property of the power spectrum of sea clutter. Finally, a novel detection method based on AR Hurst exponent is proposed and the factors influencing the fractal properties of power spectrum are analysed. The results show that the Hurst exponent of AR spectrum is effective for weak target detection in sea clutter background. Compared with the existing fractal method and the traditional constant false alarm rate (CFAR) method, the proposed method has a better detection performance.
Recognition performance analysis of instantaneous phase and its transformed features for radar emitter identification
Authors: Ru Xiao‐Hu , Liu Zheng , Jiang Wen‐Li , Huang Zhi‐Tao
Published: August 2015

Instantaneous phase (IP) feature is a time‐varying curve describing the unintentional modulation on the phase. IP is a basic feature for identifying different radar emitters, and mostly other features can always be obtained from its transformations. Thus an important issue is to choose a suitable transformation of IP which can achieve the best recognition performance, more specifically, the highest recognition ratio. Heretofore, the recognition ratios of transformed IP features were derived basically through experiments, lacking theoretical calculation and analysis. In this study, the authors first extract the IP feature from a given radar pulse, and then propose a unified model for various transformations of IP. After that, they calculate the recognition ratio theoretically based on this model. Subsequently, they prove that any linear transformation, such as derivative, smoothing, and linear dimensionality reduction cannot improve the recognition performance compared to the original IP. They also find the essentially mathematical reasons of the seemingly unimaginable results. Finally, they validate the analysis results through both computer simulations and experiments on measured data collected from 120 radar emitters in the real environment. This work provides a theoretical basis for feature extraction and feature assessment in radar emitter identification.
High manoeuvre target tracking in coordinated turns
Authors: Zhu Lihua , Cheng Xianghong
Published: August 2015

In target tracking, most tracking algorithms are model based, and serious errors can arise when the models fail to fit the physical target motions, especially during coordinated turns. To address this problem, a two‐step tracking algorithm is proposed. First, considering the diversity of the target manoeuvres, five elemental Singer models with carefully designed parameter α interact with each other in an interacting multiple model (IMM) algorithm to accomplish the tracking and estimate the target's kinematic parameters. Second, if a turn motion occurs, then it discriminates the turn motion into a horizontal turn or a three‐dimensional (3D) turn; and the real‐time turn rate is calculated to refine the corresponding model for tracking. Since the filtering stage is important in estimating the kinematic parameters, sparse‐grid quadrature Kalman filter is employed to improve the filtering capability. The proposed algorithm is exemplified by simulation tests and data tests in 3D, and is compared with that of an IMM algorithm utilising constant velocity, constant acceleration and 3D coordinated turn models. All of the test results demonstrate that the proposed algorithm is effective and has higher accuracy.
Fast two‐dimensional sparse Bayesian learning with application to pulse Doppler multiple‐input–multiple‐output radars
Authors: Jabbarian‐Jahromi Mohammad , Shahbazi Nafiseh , Kahaei Mohammad Hossein , Abbasfar Aliazam
Published: August 2015

Sparse Bayesian learning (SBL) for multiple‐input–multiple‐output (MIMO) radars can achieve significant performance in target localisation by exploring sparsity in the target space. In this study, the authors develop a fast two‐dimensional (2D) SBL algorithm using Laplace priors (2D SBL‐LPs) by deriving two auxiliary algorithms. The proposed algorithm is implemented for pulse Doppler MIMO radars in order to estimate the target parameters in three dimensions of angle, Doppler, and range. Simulation results show that the 2D SBL‐LP compared with famous Bayesian compressed sensing algorithm not only drastically reduces the computational complexity, but has better performance in targets parameters estimation. Furthermore, in estimation of range‐angle‐Doppler parameters, the 2D SBL‐LP outperforms the matched filter, 2D smoothed L0, 2D iterative adaptive approach, fast orthogonal matching pursuit (FOMP), and spectral projected gradient for l1‐norm minimisation algorithms.
Sparse representation based two‐dimensional direction‐of‐arrival estimation method with L‐shaped array
Authors: Cheng ZengFei , Zhao Yongbo , Zhu YuTang , Shui Penglang , Li Hui
Published: August 2015

In this study, a new two‐dimensional (2D) direction‐of‐arrival (DOA) estimation method with L‐shaped array is proposed based on the sparse representation framework. The basic idea is to transform the 2D DOA estimation problem into two one‐dimensional DOA estimation problems by introducing a new compound electric angle. The compound electric and elevation angles are estimated through solving two sparse recovery problems subsequently. Then the azimuth angle estimation and the angle pairing process are completed simultaneously based on the relationship between the estimated elevation and compound electric angles. Owing to the exploitations of the sparse representation technique and the cross correlation information of the incident signals, the proposed method exhibits a superior performance, including higher angle resolution ability and improved robustness against low signal‐to‐noise ratio or small number of snapshots, as well as not requiring the knowledge of the source number. Numerical simulations are performed to verify its effectiveness.
Evaluation of rodents’ respiratory activity using a bioradar
Authors: Anishchenko Lesya , Gennarelli Gianluca , Tataraidze Alexander , Gaysina Ekatherina , Soldovieri Francesco , Ivashov Sergey
Published: August 2015

The estimation of breathing activity of laboratory animals after drug administration attracts considerable interest in the context of the pharmacological experimentation. So far, this task has been mostly accomplished by means of expensive and cumbersome procedures requiring the application of sensors on the animal body. In this study, the authors present a feasibility study on the possible usage of bioradar devices for contactless monitoring the respiratory rhythm of living rodents. Experiments are performed in laboratory conditions on sleeping rats by using a continuous wave Doppler radar operating at 13.8 GHz. The recorded signals are processed by means of a data processing strategy, based on a novel motion artefacts filtering procedure, with the final aim to characterise the breathing pattern variability during the sleep phases. The achieved results are consistent with biological information available from the literature confirming the potential application of bioradiolocation instead of standard on‐body monitoring methods.
Passive multistatic radar experiment using WiMAX signals of opportunity. Part 1: Signal processing
Authors: Higgins Thomas , Webster Tegan , Mokole Eric L.
Published: August 2015

Radio frequency (RF) spectrum crowding has resulted in the need for interoperability between radar and communications systems. Passive radar has been investigated as a means to exploit the proliferation of RF systems to perform functions such as detection and tracking of moving targets. Passive multistatic radar may alleviate spectral fratricide by replacing some active monostatic radar systems. Part 1 of this study presents results from a passive multistatic radar experiment that exploits worldwide interoperability for microwave access (WiMAX) communications waveforms to detect moving targets. Signal processing strategies for high‐duty cycle, low pulse repetition frequency (PRF) waveforms are discussed and validated on experimental data. Part 2 of this article attempts to address the outstanding research issue of combining data from multistatic radar systems to increase performance.
Passive multistatic radar experiment using WiMAX signals of opportunity. Part 2: Multistatic velocity backprojection
Authors: Webster Tegan , Higgins Thomas , Mokole Eric L.
Published: August 2015

Passive radar can reduce radio frequency (RF) spectrum crowding and facilitate RF system interoperability by eliminating the necessity to transmit. Part 1 of this study discussed a passive multistatic radar experiment using Worldwide Interoperability for Microwave Access (WiMAX) signals of opportunity and the accompanying signal processing techniques that were employed. Part 2 discusses the multistatic velocity backprojection technique for visualising multistatic radar data and applies this technique to simulated data and passive multistatic data from the experiment discussed in Part 1.
Non‐coherent pulse compression — aperiodic and periodic waveforms
Authors: Levanon Nadav , Cohen Itzik , Arbel Nadav , Zadok Avinoam
Published: August 2015

The growing interest in adopting pulse compression waveforms to non‐coherent radar and radar‐like systems (e.g. lidar) invites this update and review. The authors present different approaches of designing on–off {1, 0} coded envelopes of transmitted waveforms whose returns can be envelope detected and non‐coherently processed. Two approaches are discussed for the aperiodic case: (a) Manchester encoding and (b) mismatched reference. For the periodic case, on–off sequences are described, which produce perfect periodic cross‐correlation when cross‐correlated with one or more integer number of periods of a two‐valued reference sequence {1, −b}. This study provides comprehensive rules for designing periodic on–off waveforms and their references. The periodic waveform's high‐average duty cycle (over 50%) makes it a ‘quasi continuous wave (CW) non‐coherent waveform’, which avoids the pulse–train conflict between average power and unambiguous range. Good experimental results with a laser range finder are presented. Reports on other uses are quoted.
Examination of GPS/EGNOS integrity in north‐eastern Poland
Authors: Grunwald Grzegorz , Bakuła Mieczysław , Ciećko Adam , Kaźmierczak Rafał
Published: August 2015

Integrity of positioning is one of the key aspects of satellite based augmentation systems. This paper presents a study carried out in north‐eastern Poland, a region which is considered as a border of the operation of the European Geostationary Navigation Overlay Service (EGNOS) system. Detailed analyses concerning operational parameters of EGNOS were done during the 12‐hour and 24‐hour measurement sessions conducted at a fixed point. The study was focused on the role of ionospheric delays in the integrity model according to the Radio Technical Commission for Aeronautics guidelines. In determination of the accuracy and integrity of positioning, two variants of calculations were adopted: one based on a standard interpolation algorithm determining ionospheric delay by the EGNOS system, and the other based on the Klobuchar model. The research found that the first method is characterised by only slightly better accuracy results, while significant differences were obtained by examining the integrity of positioning. For both variants of the calculation design, the values of protection levels determined for the fixed point are much higher than the positioning accuracy, which meets the integrity requirements of the navigation system.
Overcoming polar‐format issues in synthetic aperture radar multichannel autofocus
Authors: Cho Hyun Jeong , Munson David C.
Published: August 2015

Multichannel autofocus (MCA) is a subspace‐based autofocus method for solving the defocusing problem in synthetic aperture radar. In addition to the one‐dimensional (1D) defocusing assumption, MCA assumes that the perfectly focused image has a low‐return region, which is naturally guaranteed by the spatially limited nature of the radar antenna footprint. In theory, MCA yields better or even perfect solutions compared to other autofocus methods. However, the authors have discovered that MCA is far more sensitive to violation of the 1D defocusing assumption compared to other methods; in fact, MCA is unsuitable for even fairly small data‐collection angles. Fortunately, this problem can be solved if they reverse the order of two steps in the image formation process and apply MCA in a domain where the defocusing effect is one dimensional. The distorted version of the image, obtained by inverse Fourier transforming the polar‐grid data without further interpolation, contains regions satisfying a low‐return assumption, but the region of low return must be carefully specified for best performance. They present simulation results of the proposed method, reversed‐step MCA, for various ranges of look angles and discuss the selection of low‐return constraints.
Non‐coherent adaptive detection in passive radar exploiting polarimetric and frequency diversity
Authors: Colone Fabiola , Lombardo Pierfrancesco
Published: August 2015

The joint exploitation of polarimetric and frequency diversity is considered in this study as a way to improve the target detection capability in a FM radio‐based passive radar. The authors resort to a generalised likelihood ratio test approach and derive a fully adaptive multi‐frequency polarimetric detector that optimally combines the signals simultaneously transmitted by a given illuminator of opportunity and received at different carrier frequencies by differently polarised surveillance antennas. The application of the proposed detection scheme to recorded live data demonstrates the effectiveness of the multi‐frequency polarimetric operation in typical scenarios, besides the expected improvement due to non‐coherent integration of target echoes received on multiple channels. In particular, it is shown to provide remarkable target discrimination capability against interfering sources as well as increased robustness with respect to the time‐varying characteristics of the exploited signals of opportunity.
Non‐cooperative identification of civil aircraft using a generalised mutual subspace method
Authors: López‐Rodríguez Patricia , Escot‐Bocanegra David , Fernández‐Recio Raúl , Bravo Ignacio
Published: August 2015

The subspace‐based methods are effectively applied to classify sets of feature vectors by modelling them as subspaces. However, their application to the field of non‐cooperative target identification of flying aircraft is barely seen in the literature. In these methods, setting the subspace dimensionality is always an issue. Here, it is demonstrated that a modified mutual subspace method, which uses softweights to set the importance of each subspace basis, is a promising classifier for identifying sets of range profiles coming from real in‐flight targets with no need to set the subspace dimensionality in advance. The assembly of a recognition database is also a challenging task. In this study, this database comprises predicted range profiles coming from electromagnetic simulations. Even though the predicted and actual profiles differ, the high recognition rates achieved reveal that the algorithm might be a good candidate for its application in an operational target recognition system.
On the design of staggered moving target indicator filters
Authors: Ispir Mehmet , Candan Cagatay
Published: August 2015

The problem of moving target indicator (MTI) filter design for radar systems with non‐uniform (staggered) pulse repetition intervals is examined. The goal is to realise and then utilise a trade‐off in the design of MTI filter between the conflicting requirements of high suppression of undesired signal (clutter echo) and minimal suppression of desired signal (target echo). To that aim, three design methodologies, namely, least squares, convex optimisation and min–max error, are studied. The numerical results indicate that the presented designs yield high‐performance MTI filters which are easily applicable to a variety of operational scenarios. A ready‐to‐use source code for the design of suggested filters is also provided.
Micro‐Doppler imaging for fast rotating targets using illuminators of opportunity
Authors: Xia P. , Wan X.R. , Yi J.X. , Tang H.
Published: August 2015

In recent years the use of illuminators of opportunity for target detection and tracking has received renewed interest. Most aerial targets have some forms of fast rotating structures that cause micro‐Doppler (m–D) effect and can be used to assist in the classification process. There is also a good potential to use m–D for imaging such rotating structure because they contain geometry characteristic information about the rotating structure. The imaging results are expected to provide richer information for classification purposes. Conventional inverse synthetic aperture radar requires small rotation angle as well as wideband waveform. Tomography provides an opportunity to image fast rotating targets for narrowband continuous wave radar using m–D information only. This study first introduces the foundations of m–D imaging. Then, the simulation results are presented. Finally, the field experiments are described, together with the illustration and analysis of typical experimental results. Both the simulations and experimental data validate the effectiveness of the method.
Evaluation of ultraviolet ageing, pollution and varistor degradation effects on harmonic contents of surge arrester leakage current
Authors: Khodsuz Masume , Mirzaie Mohammad
Published: August 2015

Metal‐oxide surge arresters are one of the most important equipments for power system protection against switching and lightning over‐voltages. Surge arresters leakage currents increase by the operating time. In this study, the important factors on leakage current variations such as surface contamination, ultraviolet ageing and varistor degradation have been studied. To accomplish this purpose, experimental tests have been performed on various polymer housed surge arresters. Fast Fourier transform analysis has been performed on measured leakage currents. Results show that ultraviolet radiation and varistor degradation affect resistive harmonic components, especially the third and fifth harmonics. Moreover, it is observed that surface contamination has influence on fundamental harmonic variation more than ultraviolet ageing. In addition, combination of ultraviolet radiation and pollution had more effect on leakage currents. The investigation and the discussion of the results can be used to easily analyse arresters condition leading to effective schedule maintenance.
Development of thermistor signal conditioning circuit using artificial neural networks
Authors: Naveen Kumar Vaegae , Lakshmi Narayana Komanapalli Venkata
Published: August 2015

Thermistor is most widely used sensor in the temperature measurement due to its high sensitivity and fast response. The non‐linearity of the thermistor gives rise to several difficulties for on‐chip interface, direct digital readout, wireless transmission and so on. Hence, an effective lineariser is needed to overcome the difficulties. In this study, an artificial neural network‐based lineariser has been developed for the thermistor connected in operational amplifier circuit. Operational amplifier‐based thermistor signal conditioning circuit exhibits a stable temperature–voltage relation over a range of 0–100°C with low linearity. A multilayer perceptron feed‐forward neural network is used for non‐linearity compensation of thermistor circuit to further improve the linearity. A linearity of ±0.3% is achieved over 0–100°C with high temperature stability. A notable feature of the proposed method is the non‐linearity error remains low over the entire dynamic range of the thermistor. The efficacy of the method is established through simulation studies and its practicality demonstrated with experimental results obtained on a prototype unit built and tested.