A novel green phase shifter system is proposed in this research. The system is developed by a combination of reconfigurable beam steering antennas and data acquisition (DAQ) boards. A combination of two reconfigurable beam steering antennas, located side-by-side, forms a spatial configuration structure with a fabricated `green' element plank of rice husk placed in between. The concept of a spatial configuration technique has been `mutated' by shifting the structure of spiral feed line and aperture slots of first beam steering antenna by as much as 45º. The PIN diode switches connected to the DAQ boards enable the intelligent capability of the spatial antennas. The activation of certain degree radiation patterns of either the first beam steering antenna or the second beam steering antenna depends on the memory of the DAQ boards --- Beam Manager. When an intruder comes from the cardinal angles of 0º/360º, 90º, 180º, or 270º, its range and angles' location will be automatically detected by the first antenna through the output ports of the 1st DAQ: P1.0, P1.1, P1.2, and P1.3. The second antenna is then activated by the output ports of the 2nd DAQ: P2.0 up to P2.3, to adaptively maneuver the beam towards four different ordinal directions of 45º, 135º, 225º, and 315º. As a result, this system collectively contributes to the development of eight angles of radiation patterns, which can be rotated in 45º steps within 0.01 ms and successfully cover 360º without any uncovered and overlapped angle; 0°/360°, 45º, 90°, 135º, 180°, 225º, 270°, and 315º. Moreover, a mutual coupling effect generated by the spatial configuration of both antennas is alleviated by the element plank of rice husk, whose width, length, and thickness are 45 mm, 150 mm, and 10 mm, respectively. Possessing the characteristics of an adaptive new phase shifter concept and assisted by the green element of a rice husk, this system is potentially an effective way to decrease the number of drop outs and lost connections, and provides larger coverage. It is a promising candidate for installation with a WiMAX application.

A simulation technique based on Finite-Difference Time-Domain (FDTD) is used to analyze mutual coupling effects in reflectarray environment. The neighbouring element method has the ability to analyze actual non-identical reflectarray unit-cell accurately compared to the traditional Floquet simulation which assumes all unit-cell is identical. It is also found that the nearest neighbouring unit-cell located in E-plane has a larger mutual coupling effects compared to the neighbouring unit-cell in H-plane. A good agreement is shown between simulation and measurement results. This technique presents a new prediction method for the radiation pattern of reflectarray antenna.

The use of Radio Frequency IDentification (RFID) technology in a large array of contexts is a matter of fact. In many cases, such as in robotic applications, the RFID tags should satisfy specific requisites so that read range, platform robustness, radiation properties, cost, and size must be properly taken into account during the design phase. In this work, the specific requirements of tags for RFID-assisted localization and navigation of mobile robots are highlighted and discussed. On such basis, an ad-hoc platform-robust RFID tag is designed, realized and exhaustively tested through both simulations and measurements. The achieved results are impressive and demonstrate the appropriateness of the proposed tag to operate in application scenarios where performance stability is mandatory.

This paper presents an efficient technique for fast generation of sparse systems of linear equations arising in computational electromagnetics in a finite element method using higher order elements. The proposed approach employs a graphics processing unit (GPU) for both numerical integration and matrix assembly. The performance results obtained on a test platform consisting of a Fermi GPU (1x Tesla C2075) and a CPU (2x twelve-core Opterons), indicate that the GPU implementation of the matrix generation allows one to achieve speedups by a factor of 81 and 19 over the optimized single-and multi-threaded CPU-only implementations, respectively.

Reinforced concrete structures (RCS) have potential application in civil engineering and with the advent of nuclear engineering RCS to be capable enough to withstanding a variety of adverse environmental conditions. However, failures/loss of durability of designed structures due to premature reinforcement corrosion of rebar is a major constrain. Growing concern of safety of structure due to pre-mature deterioration has led to a great demand for development of non-destructive and non-contact testing techniques for monitoring and assessing health of RCS. This paper presents an experimental investigation of rebar corrosion by non-stationary thermal wave imaging. Experimental results have been proven, proposed approach is an effective technique for identification of corrosion in rebar in the concrete samples.

Linear double-layered feature extraction (DFE) technique has recently appeared in radar automatic target recognition (RATR). This paper develops this technique to a nonlinear field via parallelizing a series of kernel Fisher discriminant (KFD) units, and proposes a novel kernel-based DFE algorithm, namely, multi-KFD-based linear discriminant analysis (MKFD-LDA). In the proposed method, a multi-KFD (MKFD) parallel algorithm is constructed for feature extraction, and then the projection features on the MKFD subspace are further processed by LDA. Experimental results on radar HRRP databases indicate that, compared with some classical kernel-based methods, the proposed MKFD-LDA not only performs better and more harmonious recognition, but also keeps higher robustness to kernel parameters, lower training computational cost, and competitive noise immunity.

The impact of wireless channel modelling on exposure to electromagnetic radiation is studied. Two methods are developed in order to assess the statistical properties of whole body Specific Absorption Rate for exposure estimation in indoor environment. The body model is exposed to a bundle of waves, named cluster, following the wireless channel modelling approach. The first method is analytical and based on the Uncorrelated Scattering Assumption of the incident waves. The second method is a classical stochastic method. The point is to identify the parameters of Wireless Channel which led to significant SAR's variation.

In this paper, two dimensional multi-port method is used to analyze substrate integrated waveguide by using Green's function approach to obtain the impedance matrix of equivalent planar structure. Modes propagation constant of substrate integrated waveguide, as a periodic structure, is calculated by applying Floquet's theorem on the impedance matrix of a unit cell. Field distribution of the propagating mode is obtained by this method. Results obtained by this method are verified, in a broad range of dimensions, by comparing with published results and also those calculated by commercial electromagnetic simulator, HFSS. Electromagnetic band gaps and mode conversion phenomenon as properties of periodic structures are also observed and investigated. Mode conversion in SIW is reported for the first time by our proposed method.

Magnetic heating used for inducing hyperthermia and thermal ablation is particularly promising in the treatment of cancer provided that the therapeutic temperature is kept constant during the treatment time throughout the targeted tissue and the healthy surrounding tissues are maintained at a safe temperature. The present study shows the temperature increment produced by different concentrations of magnetic nanoparticles (ferrofluid and magnetoliposomes) inside a phantom, after irradiating tissue-mimicking materials (phantoms) with a minimally invasive coaxial antenna working at a frequency of 2.45 GHz. This frequency was chosen because maximum dielectric loss of water molecules begins at 2.4 GHz and because this is an ISM (industrial, scientific and medical) frequency. Temperature sensors were placed inside and outside the tumor phantom to assess the focusing effect of heat produced by nanoparticles. Results have shown that the temperature increments depend on the nanoparticles concentration. In this way, a temperature increment of more than 56 ºC was obtained with a ferrofluid concentration of 13.2 mg/mL, whereas the increment in the reference phantom was only of ≈ 21 ºC. Concerning the magnetoliposomes, the temperature achieved was similar to that obtained with the ferrofluid but at a lesser concentration of nanoparticles. These results demonstrate that it is possible to achieve higher temperatures and to focus energy where the nanoparticles are located.

Benefitting from the simultaneous utilization of quarter-wave (λ/4) and half-wave (λ/2) microstrip resonators, a via-free balanced bandpass filter (BPF) with direct-coupled scheme is presented in this study. In the beginning, a single-ended filter with transmission zeros (TZs) is newly proposed and the mechanism of creating two TZs around the passband without necessitating cross couplings is adopted. The TZs can be made structure-inherent based on the coexisted out-of-phase couplings among a coupled-resonator pair. On the foundation of the presented single-ended filter, a balanced filter featuring extended differential-mode (DM) stopband, good common-mode (CM) suppression, and improved passband selectivity has been designed and implemented. The DM stopband extension is achieved by misaligning the higher-order harmonic frequencies of each resonator in the DM bisected circuit while the CM suppression is accomplished by both harmonic misalignment and careful designed coupled structure in the CM bisected circuit. Eventually, a demonstrated balanced filter centering at 1.5 GHz possesses DM stopband extended up to 8f^d₀, where f^d₀ denotes the DM operation frequency, and its CM rejection ratio (CMRR) within DM passband better than 51.9 dB is attained. For measurement convenience, the DM characterizations have been accomplished by 2-port network analyzer with simple rat-race baluns and are found relatively accurate within the -15dB bandwidth of the utilized baluns.

In this paper we estimate the uncertainty in complex permittivity measurements performed in a shielded dielectric resonator, by using the Monte Carlo method. We selected this approach since the theoretical expressions required to interpret the experimental results are highly non-linear. Furthermore the resonant frequency of the system and its quality factor are highly correlated. Thus we propose a model for the measurement process which considers the major sources of uncertainty previously reported in published experimental results. The proposed model combined with the Monte Carlo method was used to propagate the probability distributions of each uncertainty contribution, obtaining a) the approximate probability density function for the measured complex permittivity, and b) the estimated expanded uncertainty for the mode TE₀₁₁. The results show that this procedure leads to small uncertainty intervals for the real part of the dielectric permittivity, while it is not very reliable in the loss tangent measurement. Additionally, for each input quantity, we calculated the standard deviation in the experimental results produced independently by each uncertainty contribution.

In this paper, we present a novel class of microstrip bandpass filters with improved upper rejection band. The proposed filters are composed of two half-wavelength resonators and two shortended microstrip feed lines for input and output. Using voltagewave analysis, we examine the resonance and coupling properties at harmonic frequencies. It is found that different combinations of the feed line and the resonator with proper selection of the coupling regions can suppress spurious responses. Benefiting from this approach, two single-band and one dual-band bandpass filters are designed, fabricated and measured. Simulated and measured results indicate that the upper rejection bands of the proposed filters are increased up to near thirdand fifth-order harmonics, respectively. And the rejection level during the stop-bands is kept below 20 dB.

This paper links the constrained trilinear tensor model into array signal processing. The structure properties of baseband signal, such as the Constant-Modulus (CM) and Finite Alphabet (FA) structures which are already known in the receiving array, are exploited in trilinear decomposition. Two novel algorithms for constrained trilinear decomposition are proposed and applied to array signal processing. The distinguishing features of the proposed model and algorithms compared to the traditional trilinear signal processing methods are: (i)~the proposed model has a better performance and lower computation complexity. (ii)~it can still work well even if degeneracy of factors are involved in the data model, which is not valid in traditional algorithms. Simulation results are presented to illustrate the application of the constrained trilinear decomposition to array signal processing and evaluate the performance of the proposed algorithms in DOAs estimation.

A parallel implementation of a quasi-static Partial Element Equivalent Circuit (PEEC)-based solver that can handle electromagnetic problems with non-orthogonal structures is presented in this paper. The solver has been written in C++ and employs GMM++ and ScaLAPACK computational libraries to make the solver fast, efficient, and adaptable to current parallel computer systems. The parallel PEEC-based solver has been tested and studied on high performance computing clusters and the correctness of the solver has been verified by doing comparisons between results from orthogonal routines and also another type of electromagnetic solver, namely FEKO. Two non-orthogonal numerical test cases have been analysed in the time and frequency domain. The results are given for solution time and memory consumption while bottlenecks are pointed out and discussed. The benchmarks show a good speedup which gets improved as the problem size is increased. With the capability of the presented solver, the non-orthogonal PEEC formulation is a viable tool for modelling geometrically complex problems.

In this paper, novel composite right/left-handed (CRLH) leaky-wave antennas based on folded substrate-integrated-waveguide (FSIW) structures are proposed. The proposed leaky-wave antennas were realized by periodically loading the radiating slots on the top metallization of the FSIW-based CRLH transmission lines. The structural advantages of the FSIW combined with the unique dispersion characteristics of the CRLH transmission line enable the proposed leaky-wave antennas to present continuous beam-scanning capability from backfire to endfire directions, occupy smaller footprint size, and provide more design flexibility than the conventional CRLH leaky-wave antennas. Two of such CRLH leaky-wave antennas were developed. In addition to the continuous beam scanning, it is found that the radiation efficiency and polarization of the FSIW-based leaky-wave antennas can be easily tuned by means of the slot size and slot orientation, respectively, indicating their potential for versatile applications. Calculated and experimental results are presented and compared. A good agreement is obtained. To the best of our knowledge, it is the first time that the leaky-wave antenna exploits both of the dispersion behavior of the CRLH transmission lines and the structural benefits of the FSIW configuration.

A circuit model for vertical transitions between different coplanar waveguide systems using via-holes is presented. The model is directly extracted from the geometry of the transition using closed expressions. Additionally, it can be used to find suitable initial dimensions for the transition in a circuit simulator, thereby greatly reducing the effort spent on subsequent electromagnetic simulations. To test the validity of the developed model, it is applied to a variety of situations involving a wide range of stack heights, dielectric constants, and transmission line geometry values. These situations cover most of the relevant broadband vertical transitions used in practical PCB and LTCC designs. Comparative analysis of the circuit model and electromagnetic simulations yields good agreement in all analyzed situations. Experimental assessment of the model is also provided for some of the transitions that were built and characterized in a back-to-back configuration.

The coherence between the complex image pair from two channels is important for improving the capability of along-track interferometry (ATI) processing in synthetic aperture radar (SAR) ground moving target indication (GMTI). The along-track dual-channel low frequency SAR can be easily influenced by not only mismatch errors of the image pair but also the radio frequency interference (RFI). RFI has great impacts on the joint probability density function (PDF) of magnitude and phase in the interferometric image. However, little work has been done to investigate the coherence improvement under RFI. This study develops an algorithm to improve the coherence of the image pair for along-track dual-channel low frequency SAR, which can be used by ATI. After analyzing RFI imaging in detail, it is proposed that the along-track interferometric image in the range frequency and cross-range slow time domain can be used to detect RFI. Median filters are proposed to further suppress RFI. This suppression has the same implementations to the image pair without heavy computation load. Considering RFI suppression and mismatch errors compensation, a pre-processing flow is proposed to achieve high coherence of the interferometric image in low frequency SAR. It is shown that the coherence of the complex image pair can be improved greatly by using this pre-processing flow. The effectiveness of this algorithm is demonstrated with real data acquired by an airborne along-track dual-channel P-band SAR GMTI system.

This paper combines a hybrid implicit-explicit (HIE) method with spectral finite-difference time-domain (SFDTD) method for solving periodic structures at oblique incidence, resulting in a HIE-SFDTD method. The new method has the advantages of both HIE-FDTD and SFDTD methods, not only making the stability condition weaker, but also solving the oblique incident wave on periodic structures. Because the stability condition is determined only by two space discretizations in this method, it is extremely useful for periodic problems with very fine structures in one direction. The method replaces the conventional single-angle incident wave with a constant transverse wave-number (CTW) wave, so the fields have no delay in the transverse plane, as a result, the periodic boundary condition (PBC) can be implemented easily for both normal and oblique incident waves. Compared with the ADI-SFDTD method it only needs to solve two untridiagonal matrices when the PBC is applied to, other four equations can be updated directly, while four untridiagonal matrices, two tridiagonal matrices, and six explicit equations should be solved in the ADI-SFDTD method. Numerical examples are presented to demonstrate the efficiency and accuracy of the proposed algorithm. Results show the new algorithm has better accuracy and higher efficiency than that of the ADI-SFDTD method, especially for large time step sizes. The CPU running time for this method can be reduced to about 45% of the ADI-SFDTD method.

In this paper, a new decoupled Unitary ESPRIT algorithm for two-dimensional (2-D) direction-of-arrival (DOA) estimation is presented. By exploiting the centro-symmetric array configurations of two parallel uniform linear arrays (TP-ULAs) and utilizing the via rotational invariance techniques, the proposed algorithm has advantages as listed below. First, the algorithm enables decoupling the estimation problem into a two-step estimation problem and obtains the automatically matched 2-D DOAs. Second, employing the elements of the array fully, the algorithm can estimate 2-D DOAs up to 2(M−1), where 2M is the sensor number of the array. Besides, the computational complexity of the proposed algorithm is lower than other representative 2-D DOA estimation methods. Simulation results are presented to show the effectiveness of the proposed method.

A new accurate Volterra-based model is introduced for behavioral modeling and digital predistortion (DPD) of power amplifiers (PAs). This model extends the GMP model with specific cross terms, and these augmented terms significantly increase the model's performance. The proposed model's performance is assessed using a LDMOS Doherty PA driven by two modulated signals (a 4-carrier WCDMA signal and a single carrier 16QAM signal). The experimental results in both behavioral modeling and DPD applications demonstrate that the proposed model outperforms the hybrid memory polynomial-envelope memory polynomial (HME) model and generalized memory polynomial (GMP) model. Compared with the HME model, the proposed model shows an average normalized mean square error (NMSE) improvement of 2.2 dB in the behavioral modeling, average adjacent channel power ratio (ACPR) improvement of 2.8/2.5 dB in the DPD application, and 20% reduction in the number of coe±cients. In comparison with the GMP model, the proposed model achieves higher model accuracy and better DPD performance, but reduces approximately 40% of coefficients.