This paper proposes a new propagation model based on the most widely used Hata model. The proposed model is developed by extrapolating Hata model to be suitable microcells. The main equation of Hata urban model is modified by substituting the suburban correction factor with a terrain roughness parameter. This parameter uses a quadratic regression estimator of the standard deviation, σ, of the terrain irregularities along the measuring path, in west of Amman, Jordan. It is shown that RMSE between the predicted and measured data for the new proposed, is improved by up to 3 dB compared to Hata suburban model in most areas under study. Furthermore, the improvement in RMSE increases as σ increases. These results clarify the robustness of the proposed model.

The distribution of fields travelling in the laminated structure with assumed values for the tangential components of the magnetic field intensities on the top and bottom surfaces of the structure, has been obtained using linear electromagnetic field theory. The treatment takes cognizance of interlaminar capacitance inherently present in a laminated structure. Analysis presented in this paper assumes identical field distribution in each lamination and a given current sheet as the source for the travelling electromagnetic fields. It has been concluded that convection currents are developed at the interface between iron and insulator regions.

A novel approach to Radar Cross-Section reduction using a thin Artificial Magnetic Conductor (AMC) structure is presented. The novel AMC structure combines two unit-cell metallization sizes and so it presents two resonant frequencies. RCS reduction is based on destructive interference of two partial reflections. Taking as starting point a previous work showing significant RCS reduction based on the combination of two AMC surfaces with overlapped AMC operation bandwidths (so that they have similar reflection coefficient amplitude) without a 180º-phaseshift, the key point of this contribution is to analyze the influence of the degree of the aforementioned overlapping on RCS reduction and to show that this achievement is based on coupling phenomena. A comparison of the achieved RCS reduction when combining two AMCs whose AMC operation bandwidth overlaps, two AMCs with non-overlapped AMC operation bandwidths, and PEC-AMC is presented. Prototypes of these three combinations have been manufactured (having them the same size) and their RCS has been measured in an anechoic chamber.

Temperature variations in tissues inside the body have been measured using microwave radiometry for more than three decades in a variety of passive body monitoring applications. In this paper we study a non-invasive prototype system for passive intracranial monitoring using microwave radiometry. It comprises one or two (two-element array) L-notch microstrip patch antennas in conjunction with a sensitive multiband receiver for detection. The particular design characteristics of the antenna are its conformality and a special L cut on its upper left edge, features that make it suitable for human biomedical applications and lead to its multiband operation in the frequency range of 2-3 GHz. The theoretical electromagnetic study indicates that the radiometric contact system in question operates well at two frequencies, with satisfying detection depths and adequate portability (small dimensions). In order to verify the findings of these simulations, experimental measurements with phantoms and various setups were carried out, resulting in the definition of the actual temperature detection level and the spatial resolution of the system. Theoretical and experimental results conclude that with the appropriate combination of conformal patch antennas and microwave receiver it is possible to monitor areas of interest inside human head models with a variety of temperature resolutions and detection depths.

Second-order scattering induced reflection divergence and nonlinear depolarization on randomly sub-wavelength corrugated semiconductor nano-pillar surface is observed, which explains the nonlinear transverse electric (TE)/transverse magnetic (TM) mode transformation of the nano-pillar surface reflection with diminishing Brewster angle. The reflected polarization ratios are degraded from 97.5% to 53% and from 96.8% to 40% under TM- and TE-mode incidences by increasing Si nano-pillar height from 30 to 240 nm. A small-perturbation modeling corroborates the scattering induced second-order polarization transformation to depolarize the reflection from highly corrugated Si nano-pillar surface. The lower polarization ratio at TE-mode reflection caused by a severer inhomogeneous Si nano-pillars oriented in parallel with surface normal is concluded. With field polarization ratio under TM-mode incidence, the angular dependent reflectance spectra with a gradually diminished and shifted Brewster angle from 74^o to 45^o can be simulated. The nano-roughened surface induced second-order scattering model correlates the diminishing Brewster angle with the surface depolarized reflection.

The estimation of d- and q-axis parameters is highly desirable, because they are fundamental parameters to many vector control algorithms in the d-q reference frame for fast and accurate responses. Using the finite element method (FEM) for the determination of the interior permanent magnet synchronous motor (IPM) reactance provides an accurate means of determining the field distribution. However, this method might be time consuming. The magnetic circuit modelling approach has been successfully used to model a variety of electrical machine such as IPM motors. This paper deals with the inverse problem methodology for the identification of d- and q-axis synchronous reactance of an IPM motor. The proposed method uses a measured electromotive force (EMF) to compute the objective function. The machine parameters identified by the proposed approach are compared to experimental results.

This paper presents a novel dual-band circularly polarized CPW-fed circular slot antenna with two open-ground rings. The proposed antenna is constructed with two opened-ground rings facing in opposite directions and embedded in the circular slot, and the enhanced feed strip of CPW. By way of adjusting the relevant parameters, we can obtain the dual-band at 1.57 GHz and 2.46 GHz respectively. A smaller frequency ratio of 1.56 is presented. The measured -10 dB return loss impedance bandwidth are 380 MHz (24.68%) for 1.57 GHz band and 210 MHz (8.33%) for 2.46 GHz band. The measured -3 dB axial ratio bandwidth for 1.57 GHz and 2.46 GHz bands are 13.38% and 8.13%, the polarization of radiation patterns are RHCP and LHCP for each band and the antenna gain are 3.72 and 3.21 dBic respectively.

Based on the beamspace transform and the rank reduction theory (RARE), a fast direction of arrival (DOA) estimation algorithm in the presence of an unknown mutual coupling is proposed for uniform circular arrays (UCAs). Via relying on the circular symmetry and expand the mutual coupling into a limited number of phase modes, the azimuth estimates are able to be obtained without the exact knowledge of mutual coupling. Then, by using the special structure of mutual coupling matrix and the characteristic of mutual coupling coefficients, the elimination of spurious estimates and estimations of the mutual coupling coefficients are able to be handled simultaneously. The Propagator Method (PM) is used to avoid the eigenvalue decomposition and its corresponding RARE matrix allows decreasing the computation cost via using a well known identity for block matrices. Moreover, an implementation of rooting polynomial substitutes the one-dimension search. Therefore, the computation burden is greatly reduced. Numerical examples are presented to demonstrate the effectiveness of the proposed method.

Non-Cooperative Target Recognition (NCTR) of aircrafts from radar measurements is a formidable problem that has drawn the attention of engineers and scientists over the last years. NCTR techniques typically involve a database with a huge amount of information from different known targets and a reliable identification algorithm able to highlight the likeness between measured and stored data. This paper uses High Resolution Range Profiles produced with a high-frequency software tool to train Articial Neural Networks for distinguishing between different classes of aircrafts. Actual data from the ORFEO measurement campaign are used to assess the performance of the trained networks.

This paper proposes a hybrid higher order finite difference time domain (FDTD) scheme that combines the classical FDTD scheme and the higher order FDTD scheme with second order accuracy in time and fourth order accuracy in space for analyzing the three-dimensional electrically large scattering problems. The classical FDTD stencils were used as buffers in the scattered field region to make the higher order FDTD stencils not intrude inside the absorbing boundary condition's regions. The superior performance of the hybrid higher order FDTD scheme has been compared with the classical FDTD one. Numerical results demonstrate that the proposed scheme would improve the accuracy and save the computer resources significantly compared to the classical FDTD scheme involved in the radar cross section (RCS) calculation. The obtained computational efficiency allows this proposed scheme to model the RCS of electrically large targets using the number of higher order FDTD cells which are much less than that of the classical FDTD cells required by three-dimensional FDTD scheme.

Over the past ten years, Ultra Wideband (UWB) Radar has been widely investigated as a biomedical imaging modality, used to detect early-stage breast cancer and to continuously monitor vital signs using both wearable and contactless devices. The advantages of the technology in terms of low-power requirements and non-ionising radiation are well recognised, with the technology being applied to a range of non-invasive medical applications, from respiration to heart monitoring. Across all these applications, there is a strong necessity to efficiently manage the large quantities of UWB data which will be captured. For wearable devices in particular, the efficient compression of UWB data allows the monitoring system to conserve limited resources such as memory and battery capacity, by reducing data storage and in some cases transmission requirements. In contrast to lossless compression techniques, lossy compression algorithms can achieve higher compression ratios and consequently greater power savings, at the expense of a marginal degradation of the reconstructed signal. This paper compares the lossy JPEG2000 and Set Partitioning In Hierarchical Trees (SPIHT) algorithms for UWB signal compression. This study examines the effects of lossy signal compression on an UWB breast cancer classification algorithm. This particular application was chosen because the classification algorithm relies heavily on shape and surface texture detail embedded in the Radar Target Signature (RTS) of the tumour, and therefore will provide both a robust and easily quantifiable test platform for the compression algorithms. The study will evaluate the performance of the classification algorithm as a function of Compression Ratio (CR) and Percentage Root-mean-square Difference (PRD) between the original and reconstructed UWB signals.

As to low observable platform, one of the major contributing sources of target RCS is the scattering due to onboard antennas. So the research on RCS reduction of the antenna is important. In this paper, a holly-leaf-shaped monopole antenna with low RCS is designed. A square notch is etched to improve impedance matching and expand the bandwidth in the ground. The measured -10 dB bandwidth is from 2.1 to 15.4 GHz (only a little higher than -10 dB around 7.5 GHz). The radiation patterns retain symmetry and are relatively stable at 2.5, 8 and 11 GHz. The monostatic RCS performance in four different incident cases is studied to obtain some helpful conclusions for the RCS reduction of the UWB antenna. The RCS achieves effective reduction in comparison with that of the reference antenna. The largest reduction is 4.1, 19.8, 3.9dBsm in three different incident cases, respectively, while the largest loss of gain is only about -1.3 dB. The antenna suits the occasion of desiring UWB antenna with low RCS.

An iterative Time-Reversal Mirror (TRM) method is proposed to Detect and Image the buried target beneath ground surface. Unlike the conventional TRM methods which treat the information of the ground as clutters and directly delete them, the iterative TRM imaging method proposed in this paper utilizes the information of rough ground surface as a useful knowledge. The new approach is consisted of two TRM procedures. In the first TRM procedure, it aims to image the rough surface where the propagation environment for electromagnetic wave is free space. The second TRM procedure aims to image the buried target. In this step, the information of the rough surface estimated by the first TRM procedure will be treated as newly updated propagation environment. Then conventional TRM is applied to image the buried target. By applying this iterative TRM method, the information of the rough ground can be well considered in the whole TRM procedure. Numerical simulations prove that this method performs significantly better image contrast comparing with the results obtained by using conventional TRM. 4-5 dB improvement on the imaging SNR has been achieved. Furthermore, the target can be located more accurately.

The sequence of Schumann resonances is unique for each celestial body with an ionosphere, since these resonances are determined by the dimensions of the planet/satellite and the corresponding atmospheric conductivity profile. Detecting these frequencies in an atmosphere is a clear proof of electrical activity, since it implies the existence of an electromagnetic energy source, which is essential for their creation and maintenance. In this paper, an analysis procedure for extracting weak resonances from the responses of electromagnetic systems excited by electric discharges is shown. The procedure, based on analysis of the late-time system response, is first checked using an analytical function and later applied to the vertical electric field generated by the computational simulation of Earth's atmosphere using the TLM (Transmission Line Matrix) method in order to extract the weak Schumann resonances contained in this electric field component.

In this paper we will report on the optical performances of submicron planar lensless pixels arranged in the 2 x 2 Bayer cell configuration, the basic element of CMOS colour image sensors. The 2D microlens array placed in front of each pixel in commercial devices has been replaced by a 2D array of submicron holes realised on a thin metal film. Each pixel has been designed to present a lightpipe inside its structure acting as an optical waveguide that confines the light up to photodiode surface. This pixel design is fully compatible with large scale industry production since its fabrication involves only standard lithographic and etching procedures. Simulations of the light propagation inside the lensless pixel has been performed by using full 3D electromagnetic analysis. In this way it was possible to determine the optical performances of the Bayer cell in terms of the normalized optical efficiency and crosstalk effects between adjacent pixels that result to be up to 30% and a factor 10, respectively, better than those ones obtained for the microlens counterpart. The significant increase of the achievable values of the normalized optical efficiency and crosstalk can foresee the possibility to reduce the pixel size down to 1 μm, i.e., beyond the limit imposed by the diffraction effects arising in microlens equipped pixel.

This paper describes the use of the correlation maps in the Ground Penetrating Radar (GPR) for the detection of near surface objects. This method is based on the definition of bi-dimensional maps that describe the level and the nature of coherence between the received electromagnetic signals. The technique proposed provides the detection of objects, reducing the impact of the clutter and improving the image contrast by an appropriate combination of the information collected in the variance and time coherence of the received signals. The method has been tested in GPR developed by ourselves and described in detail. The implemented GPR system features a high dynamic vector network analyzer (VNA) and a mechanically scanned Vivaldi antenna; the scanning is bi-dimensional, so that A, B and C scans are available.

In this paper, a high selectivity quadruple-mode bandpass filter (BPF) with source-load coupling is proposed. This filter uses two short-circuited stubloaded stepped-impedance resonators (SIRs) which have the same type but different size. Two SIRs can generate four operating modes, which can be approximately adjusted individually. Owing to the special design of the filter, the coupling of two resonators is weak. In each resonator, the even-mode frequency can be flexibly controlled by changing the length of the short stub, whereas the odd-mode one remains stationary. Due to the source-load coupling, two transmission zeros are close to the cut-off frequencies of the passband, which leads to high selectivity. Simulated results show that central frequency is 2.27 GHz with 3-dB fractional bandwidth of 22.9%. The measured and simulated results are well complied with each other.

A compact ultra-wideband (UWB) bandpass filter (BPF) with simultaneous narrow notched band and out-of-band performance improvement is presented. The UWB BPF is built up using the hybrid microstrip and coplanar waveguide (CPW) structure. By employing split-ring resonator (SRR) defected on the lower plane, the narrow notched band was introduced. The center and bandwidth of the notched band can be controlled by adjusting the length and width of the SRRs. A novel cross-shape patch is constructed to implement transmission zeros in the upper out-of-band so as to suppress the spurious passband. The measured results show that insertion loss is less than 1.7 dB, the return loss is more than 13 dB and the variation of group delay is less than 0.2 ns. Furthermore, the width of narrow notched band is about 0.15 GHz and the attenuation is more than 18 dB at the center frequency of 5.76 GHz. The upper stopband is up to 15.2 GHz with rejection greater than 20 dB.

A design procedure for a dual-band CPW-fed linearly and circularly polarized (CP) antenna based on the L-shaped slot antenna is presented in this paper. The slot antenna and the feeding structure are fabricated on the same plane of the substrate so that circuit processes and position alignment can be simplified. By shortening the length of one arm of the L-slot, an additional mode with two orthogonal electrical fields with a phase difference of 90 degree is excited, so that the circularly polarized wave can also be excited. The enhancement of the resonant bandwidth is achieved by utilizing a stub-protruded feedline, adding one finger slit at the other arm slot, and tuning the dimension of the ground plane. A bandwidth of 22.0% (2.23-2.78 GHz) is achieved with an axial ratio < 3 dB for the optimized case.

While a radar target is illuminated under the condition of spherical wave, two-dimensional ISAR image can be obtained in near field, and the wavefront curvature must be compensated. A novel two-dimensional mathematical model is set up, and a 2D-ESPRIT super-resolution algorithm based on matrix pencil is applied to estimate the accurate locations of the scattering centers in near field. Numerical simulations are conducted in different distances as well as with different SNRs. It is proved that the method can revise the spherical wavefront curvature with a high accuracy. Finally, near field ISAR imaging experiments were done outdoor, and raw data were processed with this super-resolution method, which verify that 2D-ESPRIT algorithm based on matrix pencil can compensate the spherical wavefront curvature effectively in near field.