An innovative antenna on flexible substrate with two resonators is presented. The antenna is composed of a metallic wire sewn on the substrate. Two dipolar modes in far field are radiated. To understand the interaction of the resonators with the principal antenna, studies with and without the sleeves are done in near field and far field.

To eliminate the average reflectance of antireflection coatings to the greatest extent, a Genetic Programming (GP) algorithm is proposed to design and optimize the graded refractive index distribution profile for broadband omnidirectional antireflection coatings. The proposed GP-index profile in this paper can obtain an extremely low average reflectance of 4.61×10^-7% over a wide range of incident angles and wavelengths which is obviously superior to the average reflectance of 8.09×10^-3%, 3.29×10^-4% and 4.35×10^-5% for linear profile, cubic profile and quintic profile. That means, Fresnel reflection almost can be eliminated by the optimal GP-index profile for omnidirectional incidence over a broad wavelength range. Moreover, it is demonstrated the proposed GP-index profile has better robustness, and it still has the best broadband and omnidirectional antireflection characteristics for the TiO₂/SiO₂ graded-index AR coating. Therefore, the proposed GP-index profile is obviously superior to the conventional linear profile, cubic profile and quintic profile, and the design methodology presented in this paper that uses a genetic programming technique is a quite convenient means to pursue an optimal nonlinear refractive index profile with broadband and omnidirectional antireflection characteristics.

A two-strip narrow-frame monopole antenna for hepta-band WWAN/LTE smartphone applications is proposed. The brightest point of the proposed antenna is that its narrow edge has a width of only 5mm, which is very practical for current smartphone applications with larger touch-screens. In addition, the proposed narrow-frame antenna has a small volume of 60×5×5 mm³ and a simple structure, which comprises of a two-strip monopole loaded with a chip capacitor and an L-shape high-pass filter. Meanwhile, the propose antenna can cover the GSM850/900/1800/1900/UMTS2100/LTE2300/2500 bands. Finally, the operating principle of the proposed antenna is investigated and both simulated and measured results are presented and discussed.

A wideband unidirectional patch antenna with two meandering strips and a Г-shaped feeding structure is designed. The investigation shows that the antenna achieves an impedance bandwidth of 54.2% for VSWR ≤ 2 and a stable gain of around 9 dBi. The far field radiation patterns with low cross polarization which levels are less than -27 dB, low back radiation and symmetrical E-and H-plane patterns are obtained over the whole operating frequency range.

In this paper detailed numerical results are presented for the estimation of the electric field generated by the first return stroke, in order to reproduce the main characteristics of field waveforms measured at distances beyond 50 km. The effect of parameters such as the lightning channel geometry, distance from the source, return-stroke current speed, its attenuation along the channel is discussed by comparing numerical and experimental results.

In this article, the approach involving Dynamic Threshold Optimization (DTO) algorithm is considered to optimize a new compact reconfigurable antenna to be applied to triple band Radio Frequency Identification (RFID) and to ultra wideband (UWB) antenna with multiple bands notched. The antenna is implemented by using the existing techniques, such as loading an L-type band-stop filter, inserting a split ring resonator (SRR) as well as connecting L branches to the radiation disk proposed by us. In case of RFID applications, triple-band RFID 915/2450/5800 MHz are achieved separately. The results prove that this kind of antenna can be applied in RFID reader to avoid interference with other wireless systems. RF MEMS switches are used to reconfigure the antenna to be suitable for the application in the notched UWB communication systems. The DTO algorithm program is implemented using MATLAB-software and linked to the CST Microwave studio software to simulate the antenna. In addition, the optimized antenna is assessed using the Finite Difference Time Domain (FDTD) program written with MATLAB to validate the results. The experimental results for the RFID and UWB antennas show good agreement with simulated ones. The radiation patterns are satisfactorily omnidirectional across the antenna's operation bands.

Investigations have been carried out on the convex lens effect of non-ionizing radiation inside the abdomen of a pregnant woman. Focusing property for a plano-convex lens, which is thicker than twice of its focal length and filled with water, is studied for electric and magnetic fields at different microwave frequencies. It is observed that real image of electromagnetic fields are formed inside the lens itself at the focal plane when a microwave source is placed at a distance much greater than the twice the focal length. A three dimensional homogeneous electrical model of pregnant woman abdomen model behaves like plano-convex lens and creates real image of the microwave source inside the abdomen.

In this paper, periodic structures are investigated in antenna design for wireless applications. These antennas were compared with CRLH miniaturization method. Three different models of patch antenna with coaxial feed on EBG ground, metamaterial substrate or EBG/AMC structure have been presented here. Also two compact dual-band antennas have been designed and fabricated based on CRLH techniques for wireless and GSM applications. The first antenna has directional pattern and operates at 1760, 2550 and 3850 MHz (three-band antenna) with gain 2.1, -3.9 and 2.5 dBi, and it is dual polarized. The size of prototype patch antenna is 20×20 mm² which is reduced about %47 in comparison to conventional patch antenna at 2.5 GHz. The second antenna is designed by the use of interdigital capacitor and spiral inductor. Dimensions of antenna are 15.5×12 mm², so the size is reduced about %69 in comparison to conventional microstrip patch antennas at 1.8 GHz. The second tri-band antenna operates at 1060 MHz, 1800 MHz and 2500 MHz in which two frequencies (1.8 and 2.5 GHz) are suitable for GMS and WLAN applications. Both structures have been designed and fabricated on FR4 low cost substrate with ε_r=4.4 and thickness of 1.6mm. All simulations are done with CST and HFSS. Equivalent circuit and experimental results are also presented and compared.

The radiation and propagation characteristic can be improved by the microstrip structure of the electromagnetic band-gap, which is becoming miniaturized today. In order to reduce the influence to the width of the band-gap brought by the miniaturization of the UC-EBG structure, a novel UC EBG structure is brought out. The band-gap width is guaranteed, meanwhile, the unit length is reduced to 0.1λ_g. Results of measurement indicate that this structure is effectively miniaturized, has an excellent performance, and can be used in the antenna or microwave circuit fields.

In this paper, a rigorous and accurate numerical two-dimensional modeling finite element method 2D-FEM is applied to the analysis and design of substrate integrated waveguide components. The finite element method represents an excellent tool for the analysis and design since it easily allows taking into account all details of each device. The advantages of this method have been proved with the successful design of two SIW waveguide topologies operating in [8-12] GHz and [10.7-12.75] GHz respectively for X-band and Ku-band applications employed in satellite communications. In order to validate the proposed method, a comparison is made between the FEM method implemented in Matlab and CST Microwave Studio® software. Agreements between the finite element method data and the CST software results were achieved. The obtained results show the effectiveness of this method to analyze such types of guides.

A new microstrip ultra-wideband (UWB) bandpass filter (BPF) with dual sharply rejected notched bands based on E-shaped resonator is proposed in this paper. The basic UWB BPF is designed using two microstrip interdigital coupled lines and one rectangular patch multiple-mode resonator (MMR). Then, to achieve dual band-notched performance, the proposed dual-mode E-shaped resonator is investigated and coupled to the rectangular patch multiple-mode resonator of the basic UWB BPF. To validate the design theory, a microstrip UWB BPF with two notch-bands centered at the frequencies of 5.8 GHz and 8.0 GHz, respectively, is designed and fabricated. Both simulation and experimental results are provided with good agreement.

In the work presented here, the suitability of an unusual energy storage medium is investigated. The energy storage system is based on the forceful compression of two magnetic Halbach arrays. The mass and volume energy density is obtained and compared to existing common energy storage systems. The charge and discharge times and depths are also discussed. In addition, limits and considerations, which are needed for practical implementation, e.g., risk of demagnetization, internal mechanical stresses, heating of the magnetic structure and financial efficiency are investigated.

In this paper, a different method for designing a novel and compact microstrip-fed slot antenna with band-notched characteristic for UWB application is proposed. In the proposed antenna, a pair of cross-shaped strips protruded inside an extra rectangular slot in the ground plane are used to crate an additional resonance in higher frequencies. By obtaining this resonance, the usable upper frequency of the antenna is extended from 9 to 14.8 GHz which provides a wide usable fractional bandwidth of more than 135%. Additionally, by using a square-ring radiating stub with a pair of protruded T-shaped strips inside the ring, a desired frequency band-stop performance has been obtained. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range. The proposed antenna can operate from 3.04 to 14.8 GHz for VSWR < 2 with a rejection band around 5.1 to 6 GHz to suppress any interference from wireless local area network (WLAN) systems. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range.

We performed an experiment for the verification of existing theoretical formulas for the electric field potential of a rotating magnetized sphere. Measurements of the electric field potential differences across cylindrical capacitors were carried out. Experimental results are essentially in accord with the potential obtained using the special relativity transformations and contradict formula for the quadrupole field potential.

The dispersion characteristics (ω-β diagram) of a left-handed material (LHM) loaded helical guide is analytically solved and numerically computed for different metamaterial medium properties as well as helical guide parameters. The modal behaviour of this structure has been studied with an aim to achieve ultra slow wave over wide bandwidth which finds potential applications in optical switches and memories for optical processing. Significant amount of phase velocity reduction has been achieved in comparison to when helix is in free space or loaded with normal dielectric column. Other modal properties such as presence of two fundamental modes - backward and forward wave and their lower cut-off frequency (LCF) as well as bandwidth spectrum are also revealed thoroughly.

The application of a recently introduced microwave imaging technique based on the Huygens principle (HP), has been extended to multilayered objects with inclusions in this paper. The methodology of HP permits the capture of contrast such that different material properties within the region of interest can be discriminated in the final image, and its simplicity removes the need to solve inverse problems when forward propagating the waves. Therefore the procedure can identify and localize significant scatterers inside a multilayered volume, without having apriori knowledge on the dielectric properties of the target object. Additionally, an analyticallybased approach for analyzing UltraWide Bandwidth (UWB) body propagation is presented, where the body is modeled as a 3-layer stratified cylinder with an eccentric inclusion. Validation of the technique through both simulations and measurements on multilayered cylindrical objects with inclusions has been performed.

A miniature folded printed quadrifilar helical antenna (FPQHA) using a novel compact feeding network is proposed. Folding and meandering techniques are used to obtain 66% of size reduction for the axial length of the printed quadrifilar helical antenna. A compact feeding network using an out-of-phase power divider based on double-sided parallel-strip lines and a Wilkinson power divider is designed. A fabricated prototype of the FPQHA employing the compact feeding network is presented. The measured positive gain bandwidth is from 380 MHz to 425 MHz with a reflection coefficient less than -20 dB and an axial ratio below 2 dB. The measured maximum gain is 3.08 dBic at 395 MHz with a half-power beamwidth of 1500. With good radiation performance and integrated feeding network, the proposed antenna can become a better candidate in satellite and mobile communications.

This paper investigates the generalized case of scattering from a planar grid, containing an infinite number of axially magnetized ferromagnetic microwires placed parallel to each other in free space. A semi-analytical solution is obtained by calculating the local field at the surface of the reference microwire which is the sum of the scattered field from the other microwires as well as the incident field. Graf's theorem is used to transform the scattered field from one coordinate system to the other. Scattering field coefficients for the reference microwire are obtained by matching the tangential field components at the surface of the reference microwire. Simulated results are expressed in terms of the Reflection, Transmission, and Absorption Coefficients for the (TM_z) and (TE_z) polarizations. For validation, results of the proposed analysis specialized to the case of normal incidence with TM_z polarization are compared with the results available in the literature.

The major difficulty of realizing a micro-air-vehicle-borne (MAV-borne) synthetic aperture radar (SAR) is the motion errors that need to be precisely measured and compensated. This paper presents two novel motion measuring algorithms specifically for near-range applications. These algorithms use only low-cost micro-electronicmechanical system (MEMS) inertial measurement units (IMU). A MAV-borne SAR system was built equipped with a commercial off-the-shelf (COTS) motion sensing board. Several MAV-borne SAR measurements were performed for the first time in a hall with a realistic scene. SAR images were generated with proposed motion measuring algorithms in off-line mode. Obvious improvements in SAR image quality in terms of focusing have been observed after motion compensation with the proposed motion measuring algorithms. These results show that MAV-borne SAR together with low-cost IMU can yield very useful images.

Ground penetrating radar (GPR) has shown to provide useful results for detection of buried objects. However, its performance suffers from strong reflection from ground surface especially for shallowly buried targets. In such cases, the detection problem depends on the separation of the target signal from the ground backscatter such as landmines and unexploded ordnances. In this paper, we discuss and analyze the use of space-frequency time-reversal matrices for the enhancement of ground penetrating radar signals and potential clutter reduction. Through the use of sliding windows, submatrices from a given B-scan (radargram) are utilized to extract localized scattering information of a given detection scenario. Each sub-B-scan is decomposed to its singular vectors and later used to render synthetic aperture time-domain singular vector distributions corresponding to different scattering mechanisms. Later, they are weighted by the singular values and subtracted from the full B-scan to achieve reduced clutter and enhanced target response. The method shows satisfactory results for shallowly buried dielectric targets even in the presence of rough surface profiles.