This paper presents comparison of two measurement techniques for ultra wideband (UWB) off-body radio channel characterization. A measurement campaign was performed in indoor environment using UWB wireless active tags and reader installed with the tag antenna and same set of measurement was repeated in the frequency domain using Vector Network Analyser (VNA) and cable connecting two standalone tag antennas for comparison/with a view to finding out the cable effects. Nine different off-body radio channels were experimentally investigated. Comparison of path loss parameters and path loss model for nine different off-body radio channels for the propagation in indoor environment both measurement cases are shown and analyzed. Results show that measurement taken by VNA connecting two standalone antennas through cables experiences lower path loss value for all nine different off-body channels. Least square fit technique is obtained to extract the path loss exponent. Increase of 12.96% path loss exponent is noticed when measurements are made using UWB tags and reader, i.e., without cable measurement scenario.

In this paper, a polarization-independent wide-angle planar metamaterial absorber exhibiting dual directional absorption is proposed. Measurement results indicate that the planar metamaterial absorber achieves absorptivities of 86.87% and 91.48% to the normally incident electromagnetic waves propagating in forward (+z) and backward (-z) directions, respectively. Due to geometry's fourfold rotational symmetry, the absorber is polarization-independent. Additionally, the absorber works well for a wide range of incident angles for both transverse electric and transverse magnetic polarizations. Besides its impressing performance, this planar metamaterial absorber is also extremely thin that it's thickness is approximately 1/32 of the working wavelength.

We present the design, fabrication and measurment of a dual-resonant broadband terahertz (THz) matamterial based on a modified split-ring resonator (MSRR) structure. The proposed MSRR is constructed by connecting the inner split ring with the outer split ring of adjacent cell. Transmission and reflection characteristics of the proposed structure are simulated using Ansoft HFSS, and the permittivities show negative values in 0.492-0.693 THz and 0.727-0.811 THz bands. The designed sample is fabricated on a gallium arsenide layer, and experiments are performed in Terahertz Time-Domain Spectroscopy. Measured transmission characteristics agree well with the simulations.

In this paper, the Raindrop Size Distribution (DSD) modeling and analysis are presented. Drop sizes are classified into different rain types, namely: drizzle, widespread, shower and thunderstorm. The gamma and Lognormal distribution models are employed using the method of moments estimator, considering the third, fourth and sixth order moments. The results are compared with the existing raindrop size distribution models such as the three parameter lognormal distribution proposed by Ajayi and his colleagues and Singapore's modified gamma and Lognormal models. This is then followed by the implementation of the proposed raindrop size distribution models on the computation of the specific rain attenuation. Finally, the paper suggests a suitable raindrop size distribution model for the region with its expressions. The proposed models are very useful for the determination of rain attenuation for terrestrial and satellite systems.

|In this paper, a careful study is made of the magnetostatic potential and eld of a magnetic dipole embedded in, and with dipole moment parallel to, the interface between two magnetic regions. Unlike the case of a magnetic dipole perpendicular to the interface, the detailed position of the current of the dipole relative to the location of the interface has a profound effect on the value of the field produced away from the dipole. As a consequence, the question of dening and determining the magnetic polarizability of a superconducting object partially embedded in a magnetic interface is examined. The results of this paper are important for the proper modeling of arrays of scatterers embedded in an interface, such as frequency-selective surfaces (FSSs) and metalms.

A class E power amplifier including coupling coils is proposed for application in a wireless power transfer system using magnetic coupling. The proposed amplifier is directly connected to the coils with no discrete components for harmonic filtering and dc feeding, which could cause efficiency degradation of the amplifier. The system with the differential amplifier shows 6.95 W of transmitted power and 44.6% transmission efficiency at 6.8 MHz with 14-cm distant coils. The power-added efficiency of the amplifier is 92.1% with a 14 V supply voltage, excluding the coupling efficiency of the wireless power transfer network.

In this paper, we will present a quasi-elliptic bandstop filter using asynchronously tuned resonators. To demonstrate this technique, a novel broadband microstrip bandstop filter is also proposed using distributed resonators. To achieve wide bandwidth using distributed resonators, strong couplings are required. This is achieved using tap coupled to avoid very narrow gaps which are costly to manufacture. The filter exhibits a factional bandwidth of approximately 35%. A simple practical transformation technique for transforming Chebyshev bandstop filter to asynchronously tuned quasi-elliptic bandstop filter will be presented.

Design of a composite dipole antenna array with direct feed is presented. In the form of printed-circuit antennas, the structure of the design consists of a doublet antenna and an elliptic loaded monopole antenna with a skirted dipole. As the load of the antenna array, this elliptic monopole provides wider bandwidth. Therefore, with the load possessing a radiation characteristic, it contributes to enhancing efficiency of the antenna array and hence the omni-directional radiation gain. A good agreement between simulated results by CST Microwave Studio^® and tested results suggests that the reflection coefficient for the frequency range between 4.35 GHz to 5.0 GHz is lower than -10 dB. The out-of-roundness on H-plane is lower than 2dB and the maximum gain is higher than 6dB for the frequency range from 4.6 to 5.0 GHz. What's more, the gain per wavelength is about 4 dB, showing the antenna's excellence in miniaturization.

Two fusion strategies for target recognition using multi-aspect synthetic aperture radar (SAR) images are presented for recognizing ground vehicles in MSTAR database. Due to radar cross-section variability, the ability to discriminate between targets varies greatly with target aspect. Multi-aspect images of a given target are used to support recognition. In this paper, two fusion strategies for target recognition using multi-aspect SAR images are proposed, which are data fusion strategy and decision fusion strategy. The recognition performance sensitivity to the number of images and the aspect separations is analyzed for those two target recognition strategies. The two strategies are also compared with each other in probability of correct classification and operating efficiency. The experimental results indicate that if we have a small number of multi-aspect images of a target and the aspect separations between those images are proper, the probability of correct classification obtained by the two proposed strategies can be advanced significantly compared with that obtained by the method using single image.

The time-harmonic electromagnetic scattering problem from a random inhomogeneous dielectric medium (here a turbulent plasma wake created by the atmospheric reentry of a vehicle) is considered. The electronic density of the plasma, that gives rise to its dielectric permittivity, has a fluctuating part ε_f (r), the variance and correlation function of which are known a priori. Because the electrical dimensions of the wake can be very large, the numerical solution of Maxwell's equations via a full-wave calculation performed with a boundary element and finite element method is prohibitive when statistical quantities such as the mean Radar Cross Section (RCS) and its variance are required, that necessitate a large number of random realizations. To remedy this difficulty, two approximations are considered and illustrated for a 2D scattering problem. First, a Mie series approach is adopted where the medium is discretized with small disks, thus reducing considerably the number of unknowns for a given random realization of ε_f (r), and a domain decomposition method is proposed to further reduce the complexity of the numerical solution of the corresponding system. Second, the statistical mean and the variance of the RCS are derived in closed-form from the Born approximation and yield accurate results when, as expected, the statistical mean of the relative dielectric permittivity is close to unity and |ε_f (r)| is small. Conversely, it is shown how these expressions can be used to validate the results obtained with the Mie series approximation. Numerical examples are presented that illustrate the potentialities of these techniques.

The arrays of compound-slots (inclined and displaced from waveguide centre) are not so common in the literature and the existing systematic method of design does not take into account the presence of surrounding elements. For this kind of slots, the reasons why the Elliott's procedure cannot be applied are physically explained. A new method based on circuit theory and scattering matrices connection to include the effects of the external mutual coupling in compound slots arrays is presented in this paper. To certify the validity of the complete technique, the performance of various designed arrays are compared to the results given by full-wave commercial solvers.

Liao's absorbing boundary condition (ABC) is a classic ABC algorithm. It has the advantages of better absorption effect, easy programming and needless to split field. However its numerical stability is poor, especially for the higher-order ones, which greatly limits the scope of its application. To solve this problem, a weighting method for improving the stability of Liao's higher-order ABC is presented in this paper. This method is simple and effective, and it can be implemented easily compared with other improvement methods before. It improves the stability of Liao's higher-order ABC remarkably, and extends its application range.

This paper addresses the application of measurement on goodness-of-fit (GoF) for amplitudes of radar clutter sample data against reference/theoretic parameterized probability density function (PDF). In general, various existing methods for this problem highly depend on empirical PDF parameters. This makes GoF assessments with these methods less perceivable and their accuracies are hard to control. A new method based on chi-squared type of measurement is proposed to overcome these difficulties. This method evaluates GoF by estimating the distance between the true PDF of the clutter data amplitude and the reference PDF. Hence the distance is statistically approximately independent with empirical PDF parameters. The new method has higher accuracy and symmetric property. It is especially useful for GoF comparison over multiple radar clutter data sets.

Conventional Far-field decomposition of the scattered electromagnetic (EM) field in the [EH] plane in terms of the horizontal and vertical components (i.e., h, v), introduces ambiguity for multi-static, multi-platform and/or scene-centric polarimetric synthetic aperture radar (SAR) image exploitation. This is due to the fact that a 2-dimensional (2D) vector field can not constitute a complete space capable of modeling 3-dimensional (3D) field transformations. To address this, extension of the Stokes vector, target scattering vectors and coherency parameters' analytic descriptions to 3D is explored and presented. The results are also applicable to compact polarimetry (CP) where mathematically consistent 3D Stokes parameters can be defined.

A dual-band dual-element multiple-input-multiple-output (MIMO) antenna system with enhanced isolation is proposed. The MIMO antenna system is based on printed 4-shaped antenna elements. Dual band isolation is achieved by using an array of printed capacitively loaded loops (CLLs) on the top side of the board for high band isolation improvement and a complementary CLL structure on the GND plane of the antenna for lower band isolation improvement. The lower band of operation covers 827-853 MHz and the higher band covers 2.3-2.98 GHz. Two prototypes were investigated to access the effect of the isolation mechanism. Measured isolation improvement of 10 dBs was observed in the lower operating band while the improvement in the higher band was approximately 2.5 dBs. The isolation improvement was at the expense of 5% reduction in efficiency. The measured gain patterns as well MIMO figures of merits such as the correlation factor, TARC and MEG were investigated as well.

Asymptotic limits of Negative Group Delay (NGD) in linear causal media satisfying Kramers-Kronig relations are investigated. Even though there is no limit on the NGD-bandwidth product of a linear medium, it is shown that the out-of-band to center frequency amplitude ratio, or out-of-band gain, increases with the NGD-bandwidth product, and is proportional to the amplitude of undesired transients when waveforms with defined "turn on/off" times propagate in the media. The optimal causal dispersion characteristic exhibiting NGD is obtained through Kramers-Kronig relations, which maximizes the NGD-bandwidth product as a function of the out-of-band gain. It is shown that the NGD-bandwidth product has an upper asymptotic limit proportional to the square root of the logarithm of the maximum out-of-band gain. The derived NGD-bandwidth upper asymptotic limit of the optimally engineered causal dispersion characteristic is validated with two examples of physical media, a Lorentzian dielectric medium, and an artificially fabricated loaded transmission line medium.

A despeckling technique based on multiple image reconstruction and selective 3-dimensional filtering is proposed. Multiple SAR images are reconstructed from a single SAR image by employing compressive sensing (CS) theory. In order to obtain multiple images from single SAR image, multiple subsets of pixels are selected from input SAR image by imposing restriction that each subset has at least 20% different pixels than any other subset. These subsets are taken as measurement vectors in CS framework to obtain multiple SAR images. A despeckled image is obtained by employing selective 3-dimensional filtering to multiple reconstructed SAR image. The proposed technique is tested on single look complex TerraSAT-X data set, and experimental results exhibit that the proposed technique outperformed benchmark despekling methods in terms of visual quality and despeckling quality metrics.

In this paper, we propose a new approach to generate quadrupling-frequency optical millimeter-wave (mm-wave) signal with carrier suppression by using two parallel Mach-Zehnder modulators (MZMs) in Radio-over-fiber (RoF) system. Among the numerous properties of this approach, the most important is that a filterless optical mm-wave at 60 GHz with an optical sideband suppression ratio (OSSR) as high as 40 dB can be obtained when the extinction ratio of the MZM is 25 dB. Simplicity and cost-effectiveness have made this approach a compelling candidate for future wave-division-multiplexing RoF systems. Theoretical analysis is conducted to suppress the undesired optical sidebands for the high-quality generation of frequency quadrupling mm-wave signal. The simulation results show that a 60 GHz mm-wave is generated from a 15 GHz radio frequency (RF) oscillator with an OSSR as high as 40 dB and an radio frequency spurious suppression ratio (RFSSR) exceeding 35 dB without any optical or electrical filter when the extinction ratio of the MZM is 25 dB. Furthermore, the effect of the non-ideal RF-driven voltage as well as the phase difference of RF-driven signals applied to the two MZMs on OSSR and RFSSR is discussed and analyzed. Finally, we establish a RoF system through simulation to verify the transmission performance of the proposed scheme. The Q-factor performance and eye patterns are given.

A novel generalized design procedure of broadband planar baluns based on wire-bonded multiconductor transmission lines (MTL) is presented hereby based on analytical equations. The proposed balun consists of two parts. The first one is an in-phase power divider, which equally splits the input power through its two outputs. The later are two MTLs with wire bonding between alternate conductors configured to introduce +90 and -90 degrees phase shift respectively, so that the balanced output signal has a 180 degree phase difference. In that sense, new closed-form design equations in order to calculate the design parameters of both multiconductor elements are obtained. These equations allow the proper dimensions of both MTLs to be computed irrespective of both the number of conductors and the coupling factor, and therefore, to determine the performance of the balun. The design procedure for wire-bonded MTL baluns has been assessed by means of full-wave electromagnetic simulations and by experimental work. In addition, the very good agreement between the theoretical results and measurements makes possible to define a time-saving design methodology.

A scalar potential formulation for a uniaxial anisotropic medium is succinctly derived through the exclusive use of Helmholtz's theorem and subsequent identification of operator orthogonality. The resulting formulation is shown to be identical to prior published research, with the notable exception that certain scalar potential fields not considered in previous work are rigorously demonstrated to be unimportant in the field recovery process, thus ensuring uniqueness. In addition, it is revealed that both a physically expected and unexpected depolarizing dyad contribution appears in the development. Using a Green's function spectral domain analysis and subsequent careful application of Leibnitz's rule it is shown that, for an unbounded homogeneous uniaxial medium, the unexpected depolarizing dyad term is canceled, leading to a mathematically and physically consistent and correct theory.