In this paper, a fully automatic goal-oriented hp-adaptive finite element strategy for open region electromagnetic problems (radiation and scattering) is presented. The methodology leads to exponential rates of convergence in terms of an upper bound of an user-prescribed quantity of interest. Thus, the adaptivity may be guided to provide an optimal error, not globally for the field in the whole finite element domain, but for specific parameters of engineering interest. For instance, the error on the numerical computation of the S-parameters of an antenna array, the field radiated by an antenna, or the Radar Cross Section on given directions, can be minimized. The efficiency of the approach is illustrated with several numerical simulations with two dimensional problem domains. Results include the comparison with the previously developed energy-norm based hp-adaptivity.

With the advancement of technology, the need of antenna arrays with shaped power patterns increases day by day for the purpose of improvement of communication. In this article, we represent a new method for designing optimized linear array with shaped beam radiation pattern of desired specifications. The main objective is to obtain suitable current excitation amplitude and phase distribution for the linear array elements so that it can produce the desired custom shaped radiation pattern as the user demands. The design procedure utilizes an improved variant of a prominent and efficient metaheuristics of current interest, namely the Differential Evolution (DE). In our modified DE algorithm, denoted as DE_rBM_2SX, new mutation and crossover strategies are employed. These modifications help to overcome some drawbacks of classical DE. Two examples of linear array with shaped radiation pattern design problem are considered to illustrate the effectiveness of our algorithm. Our results are also compared with two state-of-the-art variants of DE and Particle Swarm Optimization (PSO) - namely JADE and CLPSO (Comprehensive Learning Particle Swarm Optimization). The comparison clearly reveals that our optimization algorithm is more efficient than JADE or CLPSO in finding optimum element excitation amplitude and phase distribution for the desired shaped pattern.

We propose a 3D-approach of the soil surface height variations, either for the roughness characterization by the mean of the bidimensional correlation function, or as input of a backscattering model. We consider plots of 50\,cm by 50\,cm and two states of roughness of seedbed surfaces: an initial state just after tillage and a second state corresponding to the soil roughness evolution under a rainfall event. We show from stereovision data that the studied surfaces can be modelled as isotropic Gaussian processes. We study the change of roughness parameters between the two states. To discuss the relevance of their differences, we find from Monte-Carlo simulations the bias and variance of estimator for each roughness parameters. We study the roughness and moisture combined influences upon the direct backscattering coefficients by means of an exact method based on Maxwell's equations written in a nonorthogonal coordinate system and by averaging the scattering amplitudes over several realizations. We discuss results taking into account the numerical errors and the precision of radar. We show that the ability of the radar to discriminate the different states of seedbed surfaces is clearly linked to its precision.

The design and full-wave analysis of piezoelectric micro-needle antenna sensors for minimally invasive near-field detection of cancer-related anomalies of the skin is presented. To this end, an accurate locally conformal finite-difference time-domain procedure is adopted. In this way, an insightful understanding of the physical processes affecting the characteristics of the considered class of devices is achieved. This is important to improve the structure reliability, so optimizing the design cycle. In this regard, a suitable sensor layout is described, and discussed in detail. The major benefit of the proposed system stems from the potential for obtaining a superior performance in terms of input impedance matching and efficiency, in combination with an electronically tunable steering property of the near-field radiation intensity which can be profitably used to enhance the illumination and, hence, the localization of possible malignant lesions in the host medium. By using the detailed modeling approach, an extensive parametric study is carried out to analyze the effect produced on the sensor response by variations of the complex permittivity of the skin due to the presence of anomalous cells, and thus useful heuristic discrimination formulas for the evaluation of the exposure level to cancer risk are derived.

A low pass filter with ultra-wide band rejection and compact size using a proposed radial loaded transformed radial stubs is introduced and investigated. The implemented unite cell low pass filter with 1-dB cutoff frequency f_c of 3.2 GHz demonstrates stopband rejection up to 11.8 f_c i.e. 38 GHz. The design is further extended to the high-order LPF through cell cascading. The implemented four-cell LPF with f_c of 3.6 GHz demonstrated 35dB rejection from 4.8GHz to 39GHz, 50 dB rejection from 5.4 GHz to 26 GHz (7.2 f_c) and 20dB rejection from 4.4 GHz to 50 GHz (13.8 f_c). The measured passband insertion loss is less than 1.7 dB, and group delay is from 0.45~0.8 nS. The size of the four-cell low pass filter is only 0.33λg × 0.135λg, (λg is the guide wavelength at center cutoff frequency) without using any lumped elements.

We present an ω-k approach based on the use of a 1D Non-Uniform FFT (NUFFT) routine, of NER (Non-Equispaced Results) type, programmed on a GPU in CUDA language, amenable to real-time applications. A Matlab main program links, via mex files, a compiled parallel (CUDA) routine implementing the NUFFT. The approach is shown to be an extension of an already developed parallel algorithm based on standard backprojection processing to account also for near-field data. The implementation of the GPU-based, parallel NUFFT routine is detailed and the computational advantages of the developed approach are highlighted against other confronted sequential or parallel (on multi-core CPU) procedures. Furthermore, the benefits of the $\omega$-k, NUFFT-based processing are pointed out by both comparing its accuracy and computational convenience against other interpolators, and by providing numerical results. By comparing the computational performance of the algorithm against a multi-core, Matlab implementation, the speedup has been about 20 for a medium size image. The performance of the approach has been pointed out in the applicative case of vegetation imaging against experimental data of a boxtree (Buxus tree), also under a source of temporal decorrelation (wind).

In this work, threshold mode structures of two-dimensional (2D) photonic crystal (PC) lasers are presented. The subjects of this paper are finite photonic crystal structures with circular holes arranged in square and triangular lattices. In each case, both transverse magnetic (TM) and transverse electric (TE) polarization are studied. The analysis is based on the coupled-wave equations and analyzes modes' behavior for the wide range of coupling coefficient values. The laser mode is characterized by threshold gain and frequency deviation, and these quantities depend on coupling constants, which means that the threshold gain of the mode and the mode's frequency deviation depend on the coupling constants. Presented analysis gives an interesting insight into behavior of the modes in photonic crystal lasers.

A simple traffic surveillance system based on the extraction of features from range-Doppler radar images is addressed. The concept exploits the High-Resolution Radars (HRR) properties. Specifically, a procedure is proposed to obtain some features from the HRR non-cooperative targets to enable their classification. These features are the distance, radial velocity, radial longitudinal dimension of the target, its integrated range-Doppler image based on a group of range-Doppler frames from each target, and both the coherent and non-coherent integrated range profiles. Experimental results from real scenarios using a high-resolution Linear-Frequency-Modulated Continuous-Wave (LFMCW) millimetre-wave radar are shown.

Electric fields have been widely used for the treatment of neurological diseases, using techniques such as non-invasive brain stimulation. An electric current controls cell excitability by imposing voltage changes across the cell membrane. At the same time, the presence of the cell itself causes a re-distribution of the local electric field. Computation of the electric field distribution at a single cell microscopic level is essential in understanding the mechanism of electric stimulation. In addition, the impact of the cellular biophysical properties on the field distribution in the vicinity of the cell should also be addressed. In this paper, we have begun by first computing the field distribution around and within a spherical model cell. The electric fields in the three regions differed by several orders of magnitude. The field intensity in the extracellular space was of the same order as that of the externally applied field, while in the membrane, it was calculated to be several thousand times greater than the applied field. In contrast, the field intensity inside the cell was greatly attenuated to approximately 1/133th of the applied field. We then performed a detailed analysis on the dependency of the local field distribution on both the electrical properties (i.e., conductivity, dielectricity), and the geometrical properties (i.e., size, membrane thickness) of the target cell. Variations of these parameters caused significant changes to the amplitude and direction of the electric field around a single cell. The biophysical mechanisms of such observations and their experimental implications are discussed. These results highlight the significance of considering cellular properties during the electric stimulation of neuronal tissues.

Radar-based microwave imaging is being investigated as a complementary diagnostic tool for breast cancer detection. One of the major challenges associated with radar-based breast imaging is the removal of the overwhelming reflection caused by the skin. This paper presents an algorithm that has been designed for realistic 3D scenarios. The algorithm is tested on a variety of realistic 3D numerical breast models, as well as measured data from a phantom and patient. In all cases, the reflections from the skin are significantly reduced, facilitating detection of known tumors.

In this hybrid combined time domain (TD) and frequency domain (FD) approach, one can generate the early-time response using the method of marching-on-in-time (MOT) and use the method of moment (MOM) to generate the middle-frequency response, as the low frequency data may be unstable. The early-time and the middle-frequency data provide the missing low and high frequency response and the late-time response, respectively. Generation of a wide-band response using partial information of the TD data and FD data has been accomplished by the use of the continuous and discrete Laguerre functions.

This paper presents the estimation of emissivity of calibration load using discretized scattering simulation data in bistatic reflection measurement, and analyzes the effect of several measured parameters on emissivity of calibration load. In the analysis of the impact of measured parameters on emissivity, a new calibration target is designed to improve the accuracy of emissivity measurement. In this bistatic measurement, the scattering from calibration load is simulated by FDTD (Finite-Difference Time-Domain) method. Based on Kirchhoff's law, the emissivity of calibration load is estimated by the discretized scattering data composed of different scanning angle interval and sampling azimuth planes. By the studies of simulation results, the estimation accuracy of emissivity of calibration load can be improved by selected appropriate measured parameters in bistatic reflection measurement.

In this paper, the applications of shunt open stubs are reported based on asymmetric half-wavelength resonators structure. To demonstrate the design ideas, the analysis methods of ABCD matrix and equivalent circuit are used. The multi-band bandpass, miniaturization and harmonic suppression by application of the shunt open stubs are demonstrated. The measured insertion loss of the dual-band filter with the center frequency of 1.9 and 5.8 GHz is less than 2.7 dB. The insertion loss of the tri-band filter with the center frequency of 1.5, 4 and 6.3 GHz is less than 2.7 dB. Furthermore, a compact bandpass filter with size around 12.3 mm*11.5 mm is designed and fabricated. The bandwidth of the filter is 120 MHz with the center frequency of 2.4 GHz and the insertion loss is less than -3 dB. Especially, the insertion loss is less than -20 dB from 2.8 GHz to 7 GHz. For the filters above, the simulated results and the measured results agree well.

A novel Ku-band push-push dielectric resonator oscillator (DRO) using substrate integrated waveguide (SIW) power combiner is presented. Compared with the traditional push-push oscillator, the proposed push-push DRO can realize high fundamental harmonic suppression, due to the use of a SIW power combiner, whose cut-off frequency is designed within the range of the fundamental and second harmonic frequency. Moreover, the isolation of two fundamental frequency oscillators can be enhanced, while the power combiner operates at the second harmonic frequency to maximize the output power. As shown in the experimental results, the centre frequency of push-push DRO is 14 GHz, with a frequency tuning range of 30 MHz. The suppression of the fundamental frequency is 28.59 dBc while the third harmonic suppression is 22.54 dBc, respectively. Furthermore, the phase noise can achieve -98.01 dBc/Hz at 100 kHz offset from the centre frequency.

A loss of large aperture quasi-optics which consist of a lens and a feed antenna is firstly measured using a radiometer receiver via the modified reference control method for a W-band imaging radiometer system. The quasi-optical loss is mainly decided by the dielectric loss of the lens with good quasi-optical transformation efficiency between the lens and the feed antenna. The quasi-optics composed of an aspheric lens and a dielectric rod antenna are designed for high resolution, low aberration, and compact size. The fabricated quasi-optics with the aperture diameter of 500 mm have the quasi-optical transformation efficiency of more than 95%. The radiometer receiver is designed applying a total power type and a direct conversion topology for simplicity, compact size and low temperature sensitivity. The manufactured receiver has the temperature sensitivity less than 1 K for both a hot source and a cold source. The calculated and measured results of the quasi-optics are very well matched by approximately 1.6 dB. The expected measurement errors by the reference control method are also analyzed as the functions of the characteristic parameters of the radiometer receiver.

This paper studies the bit error rate (BER) performance of non-coherent impulse-radio ultra wideband (IR-UWB) correlation receivers in the IEEE 802.15.3a channel for combined binary pulse amplitude modulation-pulse position modulation (BPAM-PPM) scheme. The BER performance is based on the channel averaged signal-to-noise ratio (SNR). The study includes simple transmitted reference (TR), differential TR (DTR), and energy detection (ED) receiver structures. Moreover, different performance parameters are addressed, namely the signal bandwidth integration window factor, number of pulses per bit, and receiver power consumption. ED receivers with BPAM-PPM are shown to outperform simple TR receivers and have a performance which approaches that of differential TR (DTR) receivers with smaller power consumption for the same design parameters.

P4 polyphase code is well known in microwave pulse compression technique. There are different reduction techniques to reduce the sidelobes of P4 code. This paper presents a new sidelobe reduction technique which its results are excellent. To valid our work, other sidelobe reduction techniques such as Woo filter and modified forms of Woo filter are investigated and compared with the technique presented in this paper. Results show that the method introduced in this paper produces better peak side lobe ratio (PSL) and integrated side lobe ratio (ISL) than other solutions.

Time harmonic electric and magnetic fields inside a parallel plate DB boundary waveguide are derived and fractional curl operator is utilized to study the fractional parallel plate DB waveguides. The DB boundary conditions are incorporated by assuming the behavior of boundary as perfect electric conductor (PEC) for transverse electric mode and perfect magnetic conductor (PMC) for transverse magnetic mode. For this purpose a general wave propagating inside the parallel plate wave waveguide is assumed and decomposed into TE and TM modes. Behavior of the fields and transverse impedances of the walls of guide are studied with respect to the fractional parameter describing the order of the fractional curl operator. The results are compared with the corresponding results for fractional waveguides with PEC walls.

A compact reconfigurable antenna integrated with stepped impedance stub (SIS) loaded stepped impedance resonator (SIR) and SIS loaded hexagon stepped impedance resonator (HSIR) for ultra wideband (UWB) applications is proposed in this paper. The reconfigurable UWB antenna can work as a UWB antenna and a dual notch band UWB antenna by controlling the switches ON and OFF. The proposed two notch bands are obtained by embedding a SIS-HSIR on hexagon radiation patch and a SIS-SIR on coplanar waveguide (CPW) excitation line. The reconfigurable characteristic is achieved by means of two ideal switches. The proposed reconfigurable antenna has been designed, fabricated and measured. The experimental results show that the proposed reconfigurable antenna has a multi-mode function and good omni-directional characteristics.

A new permittivity is defined for anisotropic dielectrics with permanent polarization, which allows obtaining simple connections between the quantities of electric field. As an application, using the defined quantity, we will demonstrate advantageous forms of the refraction theorems of the two-dimensional electric field lines at the separation surface of two anisotropic dielectrics with permanent polarization, anisotropic by orthogonal directions.