In this work two model selection criteria, i.e., Akaike's information criterion (AIC) and minimum description length (MDL), are applied to measurements in a RC with Rayleigh, Rician, Nakagami, Bessel K, and Weibull distributions as the distribution candidate set. In spite of small differences of the AIC and MDL tests (due to their different penalty terms on distribution parameters), both criteria result in similar conclusions. Results show that the Rayleigh distribution provides the overall good fit to the Cartesian field amplitude, especially for an overmoded RC, and that the Weibull distribution provides good fit to the Cartesian field amplitude in an undermoded or loaded RC. In addition, it is found that both the Rician and Weibull distributions provide improved approximations of the Cartesian field amplitude in a loaded RC with non-negligible unstirred components and that the transition from undermoded RC to overmoded RC depends not only on the operating frequency and mode-stirrer efficiency (as it is commonly believed) but also on source stirring and RC loading.

The fundamental limits of the gain and efficiency of an antenna are explored. These are very important quantities for e.g., superdirective arrays. The antenna is in this paper confined in a sphere and all of the currents are assumed to run in a material with a given conductivity. It is shown that one can find the current distribution in the sphere that optimizes the gain, given the frequency and the radius of the sphere. The results indicate the distribution of antenna elements in an antenna array in order to maximize gain, or efficiency. The analysis is based on the expansion of the electromagnetic fields in terms of vector spherical harmonics. Explicit expressions for the limits of gain and efficiency, and the corresponding current densities, are derived for different types of antennas.

Based on Time-Domain Reflectometry (TDR) technique, a novel method which could locate faults on the coaxial cable distribution network by using Support Vector Machine (SVM) is proposed in this paper. This approach allows the faulty network to be reconstructed by estimating the lengths of branches. A State-transition Matrix model is employed to simulate the TDR response at any port and evaluate the transfer function between two points. SVM is used to solve the inversion problem through training datasets created by the State-transition matrix model. Compared to the existing reflectometry methods, our proposed method can tackle multiple faults in the complex cable networks. Numerical and experimental results pointing out the performance of the SVM model in locating faults are reported.

A three-dimensional (3-D) source localization algorithm of joint elevation, azimuth angles and range estimation for the mixed near-field (NF) and far-field (FF) sources is presented in this paper. We first estimate the elevation angles of all mixed sources by using the generalized ESPRIT method. With the elevation angle estimates, the range parameters of all mixed sources are obtained, and then both the NF and FF sources are distinguished. Finally, with the elevation angle and range estimates, the azimuth angles of all mixed sources are acquired based on the conventional high-resolution MUSIC method. The proposed algorithm avoids parameter match operation, and requires neither a multidimensional search nor high-order statistics (HOS). Simulation and experiment results show the performance of the proposed algorithm in this paper.

This paper presents an evaluation of measurement uncertainty for complex-valued quantities in microwave applications, mainly focusing on the non-linear transformation of measurement uncertainty from rectangular coordinate to polar coordinate. Based on the law of propagation of uncertainty in matrix form, general expressions of the covariance matrix for the magnitude and phase uncertainties in polar coordinate have been derived, and several different application scenarios have been analyzed and evaluated with numerical simulations. This is followed by some recommendations on the coordinate transformations in practical microwave measurements.

Presently, the simulated Delay Doppler Maps (DDMs) of oil slicked sea are limited to simplified scenarios which have the elevation angle of 90° (nadir reflection). In this paper, the detailed simulation process to generate GNSS-R DDMs of oil slicked sea surfaces under general scenarios is presented. The DDM of oil slicked sea surface under general scenarios are generated by combining the mean-square slope model for oil slicked/clean surfaces and the GNSSR Zavorotny-Voronovich (Z-V) scattering model. The coordinate system transformation appropriate for general-elevation-angle scenarios are also incorporated. To validate the proposed approach, a comparison is made between the DDMs of a simplified scenario and a general scenario, which are generated based on the oil slick distribution of the Deepwater Horizon oil spill accident. Theoretical analysis reveals that oil slick may be detected within a 100 km radius coverage area around the specular point for a GNSS-R receiver under the general scenario with elevation angles of 72°.

In this research, a compact printed antenna design operating on ultra-wideband (UWB) and three extra wireless communication bands is proposed. An ellipse-shaped monopole is utilized to realize UWB application (3.1-10.6 GHz). The modified ground employs three folded Capacitive Loaded Line Resonators (CLLRs) to obtain triple relatively lower communication bands, including parts of global System for Mobile Communications (GSM) band at the centre frequency of 1.78 GHz, Wideband Code Division Multiple Access (WCDMA) band at the centre frequency of 2.15 GHz, and Wireless Local Area Networks (WLAN) band at the centre frequency of 2.4 GHz. The CLLRs are designed with quarter-wavelength to control the corresponding frequencies independently. Good agreement is achieved between the simulation and measurement to verify our presented design. The basic, dual-, triple-band UWB antennas are also simulated and good results are obtained. Small group delay variations across UWB frequencies are obtained for the presented antenna and reference antennas, with some level of distortion observed.

The emerging field of compressed sensing provides sparse reconstruction, which has demonstrated promising results in the areas of signal processing and pattern recognition. In this paper, a new approach for synthetic aperture radar (SAR) target classification is proposed based on Bayesian compressive sensing (BCS) with scattering centers features. Scattering centers features are extracted as a l₁-norm sparse problem on the basis of the SAR observation physical model, which can improve discrimination ability compared with original SAR image. Using an overcomplete dictionary constructed of training samples, BCS is utilized to design targets classifier. For target classification performance evaluation, the proposed method is compared with several state-of-art methods through experiments on Moving and Stationary Target Acquisition and Recognition (MSTAR) public release database. Experimental results illustrate the effectiveness and robustness of the proposed approach.

In recent years, particle probability hypothesis density (PHD) filtering has become an active research topic for multiple targets tracking in dense clutter scenarios. However, it is highly required to improve the real-time performance of particle PHD filtering because it is a kind of Monte Carlo approach and the computational complexity is very high. One of major difficulties to improve the real-time performance of particle PHD filtering lies in that, resampling, which is usually a sequential process, is crucial to the fully-parallel implementation of particle PHD filter. To overcome this difficulty, this paper presents a novel threshold-based resampling scheme for the particle PHD filter, in which the particle weights are all set below a proper threshold. This specific threshold is determined using a distinguishing feature of the particle PHD filters: The weight sum of all particles in weight update is equal to the total target number in the current iteration. This proposed resampling scheme allows the use of fully-pipelined architecture in the hardware design of particle PHD filter. Theoretical analysis indicates that the particle PHD filter employing the proposed resampling technique can reduce the time complexity by 33% around in a typical multi-target tracking (MTT) scenario compared with that employing the traditional systematic resampling technique, while simulation results show that it can maintain the almost same performance of estimation accuracy.

This paper presents the design and analysis of an inside-out axial-flux permanent-magnet (AFPM) synchronous machine optimized by genetic algorithm (GA) based sizing equation, finite element analysis (FEA) and finite volume analysis (FVA). The preliminary design is a 2-pole-pair slotted TORUS AFPM machine. The designed motor comprises sinusoidal back-EMF waveforms, maximum power density and the best heat removal. The GA is used to optimize the dimensions of the machine in order to achieve the highest power density. Electromagnetic field analysis of the candidate machines from GA with various dimensions is then put through FEA in order to obtain various motor characteristics. Based on the results from GA and FEA, new candidates are introduced and then put through FVA for thermal behavior evaluation of the designed motors. Techniques like modifying the winding configuration and skewing the permanent magnets are also investigated to attain the most sinusoidal back-EMF waveform and reduced cogging torque. The performance of the designed 1 kW, 3-phase, 50 Hz, 4-pole AFPM synchronous machine is tested in simulation using FEA software. It is found that the simulation results fully agree with the designed technical specifications. It is also found from FVA results that the motor temperature reaches at highest temperature to 90°C at the rated speed and full load under steady state condition.

Time reversal imaging method based on full wave numerical technique for likely breast tumors biological tissue in the Microwave-Induced Thermo-Acoustic Tomography (MITAT) system is discussed. In this paper, the mechanism of microwave-induced thermo-acoustic is strictly described based on thermodynamics and thermo-diffusion principles; the equivalent relationship between the absorbed microwave energy distribution of the biological tissue and the induced thermo-acoustic source distribution is used as the basis of the imaging algorithm. Due to its unique noise suppression feature and the stability of the algorithm, the Time Reversal Method (TRM) based on the Pseudospectral Time-Domain (PSTD) technique is applied to image heterogeneous phantom tissues from low Signal-to-Noise-Ratio (SNR) thermo-acoustic signals. Thereafter, an integrated MITAT prototype system is presented to obtain the thermo-acoustic signals from some biologic tissue with millimeter scale. The proposed TRM method is based on PSTD technique produced two-dimensional images, presented to study the performances of the MITAT in terms of contrast and resolution. These images prove predominant advantages in both contrast and resolution compared with conventional microwave and ultrasound imaging systems for malignant tumor detection. Based on the current results, our TRM-PSTD MITAT system provides evidence to predict breast tumor in an early stage and millimeter scale.

Metal fiber content is often a measured parameter for electromagnetic shielding fabric (ESF). A commonly used method is combustion measuring, but measuring speed was slow and measured fabric damaged. This study proposes a new method based on computer image analysis for recognition of metal fiber content per unit area (MFCPUA) of the ESF, which aims at analyzing the MFCPUA without damage and providing a basis for the shielding performance evaluation of the ESF. Local region images of garment or fabric are obtained using high definition shooting system to build a gray matrix model which can describe the image. A recognition algorithm for fabric density based on gray extreme judgment is then given to construct a computation for the MFCPUA. The recognition results obtained with the proposed method is compared with the experimental results from manual combustion measuring, and the error reason and the application are also analyzed. Results of experiments and analyses show that the proposed method can identify the local fabric density with lossless and accurately calculate the MFCPUA, which provide a new method for electromagnetic shielding performance evaluation of the fabric and garment by computer technique.

A compact dual-band MIMO coupling element based antenna with high port isolation is proposed for the first time. The proposed antenna comprises four nonresonant coupling elements, the matching circuit, chassis of the mobile terminal, and de-coupling structures. The proposed antenna can cover two working bands of E-GSM900 and PCS1900. The measured results show that the isolation between the coupling elements operating at the same frequency is higher than 20 dB. The proposed structure can be applied to the MIMO system.

A new design of a wideband Wilkinson power divider using double-sided parallel strip line technique is presented in this paper. To obtain a good isolation value, the proposed design was integrated with three isolation resistors. The proposed power divider is designed for a wide range of frequencies between 2 GHz to 6 GHz with all the ports matched to 50 Ω. The conventional quarter wavelength arms are divided to three different widths to ensure wideband capabilities. Moreover, the novelty of the proposed design come from the double-sided parallel-strip line technique where proposed design is using similar structure at both the top and bottom layers to ensure balance of transmission. All dimensions for the transmission line section were optimized to achieve wideband operation and were integrated with a lumped element. This design can be used as a double-sided feeder for a microstrip antenna.

This paper presents analysis results relative to an underground MIMO channel. Measurement campaigns were conducted in a former gold mine at a center frequency of 5.8 GHz under Line-Of-Sight (LOS) scenario. Extracted data have been processed to obtain the relevant statistical parameters of the channel. The resulting propagation behavior differs from frequently encountered in more typical indoor environments, such as offices and corridors. Indeed, the path loss exponent is less than 2 in MIMO configuration due to the large number of scatters that increase the received power when compared to the free-space case. Moreover, there has been a significant increase in spectral efficiency, when using MIMO technique. Hence, according to calculated statistical parameters, wireless link performance is improved through the use of the MIMO scheme. All in all, multi antenna systems present an ideal alternative for future underground communication systems.

This paper mainly deals with the detection problem of the target in the presence of the Compound-Gaussian (CG) distribution clutter with the unknown Power Spectral Density (PSD). Traditionally, the CG distributions, in particular the K distribution and the complex multivariate t distribution, are the widely used models for the clutter measurements from the High Resolution (HR) radars. Recently, the CG distribution with the Inverse Gaussian (IG) texture, the specific class of CG clutter, is represented as the IG-CG distribution and validated to provide the better fit with the recorded clutter data than the mentioned two competitors. Within the IG-CG framework, the detector is here proposed in terms of the two-step Generalized Likelihood Ratio Test (GLRT) criterion, and the empirical estimation method is resorted to estimate the unknown PSD in order to adapt the realistic scenario. The proposed detector is tested on the real-life IPIX radar data, in comparison with the existing Adaptive Normalized Matched Filter (ANMF) processor, and the detection results illustrate that it outperforms ANMF.

This paper deals with the application of a meta-heuristic optimization algorithm, namely the Cuckoo Search Algorithm in design of the Electromagnetic band gap (EBG) structures. These EBG structures are employed for the purpose of suppressing power/ground noise in printed circuit boards. A design example of 2D planar EBG structure in the specified frequency band is presented and implemented. The measured results are found to be in good agreement with the simulation as well as the analytical results.

In the ground moving target indication with synthetic aperture radar (SAR) community, algorithms used to estimate the velocity of a detected moving target are important because they are relative to the topics about refocusing and azimuth displacement correction. The velocity is regarded as a vector with two components, one in azimuth and one in range direction, and new algorithms aiming at estimating the two components are proposed and verified. The range velocity estimator transforms a detected patch containing a moving target to range Doppler domain by using the 1-D fast Fourier Transform in each range bin to achieve its range Doppler locus. The slope of the range Doppler locus is computed by using the Radon Transform on the range Doppler plane and the range velocity component is worked out according to radar system parameters and the slope value. Two estimators are proposed to compute the azimuth velocity component. One is based on symmetric defocusing in Doppler domain, the other is based on phase gradient in wave-number domain. Experiments confirm the effectiveness of the estimators by using simulated and field data.

Permanent magnet (PM) array affects flux field distribution of electromagnetic linear machine significantly. A novel dual Hal-bach array is proposed in this paper to enhance flux density in the air gap, and thus to improve output performance of linear machines. Magnetic field in the three-dimensional (3D) space of a tubular linear machine with dual Halbach array is formulated based on Laplace's and Poisson's equations. Numerical result from finite element method is employed to simulate and observe the flux distribution in the machine. A research prototype and a testbed are developed, and experiments are conducted to validate the analytical models. The study is useful for analysis and design optimization of electromagnetic linear machines.

We numerically analyze the optical response and nonlinear susceptibilities of fishnet metamaterials with the holes infiltrated by a third-order nonlinear dielectric. Through full-wave simulations and by employing a nonlinear parameter retrieval method, we confirm and quantify the enhanced nonlinearities, showing bulk third-order nonlinear susceptibilities that are up to two orders of magnitude larger than the nonlinear dielectric. We also use the retrieved parameters to calculate the material figure of merits and the conversion efficiencies, showing material figure of merits up to two orders of magnitude larger and conversion efficiencies up to four orders of magnitude larger than the nonlinear dielectric alone. Though these results are calculated using one-unit-cell thick structures, the large magnitude of the enhancement still makes these structures attractive, allowing reasonable conversion efficiencies supported by even subwavelength slabs.