The light propagation through a one-dimensional symmetrical photonic structure, determined by the symmetric Silver mean Ag₄ distribution embedded between two Bragg structures Bg₂₇ (Bg₂₇/Ag₄/Bg₂₇), is studied using the transfer matrix method (TMM). The focus lies on the investigation of the influence of symmetry of the structure as well as the dependence of transmission on the frequency, angle of incidence of the light striking the structure and symmetrical deformation of the structure. The deformation was introduced by applying a power law, so that the coordinates y of the deformed object were determined through the coordinates x of the non-deformed structure in accordance with the following rule: y = x^1+k. Here, k is the degree of the law. A comparison will be made with a symmetrical periodic structure having the same number of layers. All results will be discussed in relation with the k values. Indeed, in the case of low k values close to zero a monochromatic filter was obtained, and in the case of relatively high values, an omnidirectional mirror is obtained.

In this paper, a development of compact wideband antenna for L-Band Applications is presented. The proposed antenna is developed based on Modified Sierpinski Based Fractal geometry for the antenna patch with additional meandered structure in the antenna transmission line. The designed antenna is printed on a 10 x 10 cm of substrate with a relative permittivity of 4.3 and thickness of 1.6 mm. The antenna is fed by a 50 Ω microstrip line. The proposed antenna is characterized both in numerical and experimental analysis. The antenna characteristics are analyzed in terms of return loss, bandwidth, antenna gain, radiation pattern and radiation efficiency. From the experimental analysis, the fabricated antenna exhibits reasonable agreement to numerical design. The proposed antenna has an operating frequency from 0.94 GHz to 2.25 GHz with the lowest return loss of -36dB and maximum gain around 5.49 dBi, as well as radiation efficiency of 97%, approximately.

A detailed study on the performance of square loop High impedance Surface (HIS) on lossy dielectric with its Artificial Magnetic Conductor (AMC) Property changing to narrow band absorber and then to Perfect Electric Conductor (PEC) depending on the loss in the dielectric is presented in this paper. An equivalent circuit modelling is used to theoretically explain how this transition is happening. This observed narrow band absorption (0.08 GHz) on the thin (0.016λ) lossy dielectric is scalable to different operating frequencies by varying the dimension of the geometry. The simulation studies on the effect of different geometrical, dielectric and incident wave parameters on the absorption property of this lossy HIS are also dealt with in this paper. Experimental investigation is in good agreement with simulated result and equivalent circuit modelling.

This paper presents compact dual/tri-band bandpass filters (BPFs) with controllable frequency and high selectivity for WLAN applications. A stepped impedance resonator with a shorting stub and a uniform impedance resonator with an open stub are applied in the designs. Several techniques that can generate transmission zeros are combined, to improve the frequency selectivity. The resonators and the proposed filters are characterized by full-wave simulations. To validate the design strategies, a dual-band BPF centered at 2.4 GHz and 5.2 GHz was first designed. With a minor modification, a tri-band BPF centered at 2.4 GHz, 5.2 GHz and 5.8 GHz was then developed. Both simulations and measurements were carried out to demonstrate the effectiveness of the designs. Good agreements are achieved.

A novel planar ultra-wideband (UWB) antenna with triple-notched bands using triple-mode stub loaded resonator (SLR) is presented in this paper. The basic UWB antenna consists of a circular-shaped radiating element, a 50 Ω microstrip feed line, and a partially truncated ground plane. Then, the resonance properties of the SLR are studied. Results reveal that the multiple-mode property of the SLR can be utilized in the UWB antenna design to achieve triple band-notched performance. To validate the design concept, a novel planar UWB monopole antenna with three notched bands respectively around the WiMAX band, WLAN band, and X-band satellite communication band is designed and fabricated. The results indicate that the proposed planar antenna not only retains an ultrawide bandwidth, but also owns triple band-rejections capability. The UWB antenna demonstrates omnidirectional radiation patterns across nearly whole operating bandwidth that is suitable for UWB communications.

This paper describes a method of measurement of miniaturized antenna gain in HF band based on a parallel plate cell. Compared to a free space outdoor approach this method offers two advantages: the use of a well defined environment and time efficiency. For the same external dimensions, it also has an advantage compared to TEM/GTEM cells designs in terms of useful antenna under test (AUT) space. This space is of a major importance in HF band since even miniature antennas can have considerable proportions. The proposed structure is composed of a parallel plate cell, whose construction is simple and not expensive. It offers a precision measurement with an error not exceeding 2.3 dB with respect to calibrated antenna gain and simulation results.

In modern information and communication technologies, manipulating focal length has been hot topic. Considering that the conductivity of graphene layer can effectively be tuned by purposely designing the thickness of the dielectric spacer underneath the graphene layer, a graphene-based lens with tunable focal length is proposed in this paper, and it can be used to collimate waves. The fabrication of the proposed graphene-based lens is purposed, and the performance of the lens is verified with finite-element method. The simulation results demonstrate that the graphene-based lens has excellent tunability and confinement. At the same time, the lens exhibits low loss in certain rang and large frequency bandwidth.

A compact triplet inline substrate integrated waveguide (SIW) bandpass filter is presented with sharp lower skirt and deep lower-stopband performance. The filter is composed of two SIW rectangular cavities and an embedded short-ended microstrip line on the top surface of two adjacent SIW cavities. A transmission zero can be generated by the cross coupling near the lower passband edge, which allows the filter implementation in inline with sharp lower skirt. Deep lower stopband performance is inherited from SIW. To validate the concept, a filter prototype with fractional bandwidth (FBW) of 4% at 5.75 GHz is designed, fabricated and measured. Good agreement can be obtained between the measured and simulated results.

This paper presents a compact, low-profile, wearable dual-band antenna operating in the Wireless WLAN band of 5.15~5.25 GHz and 5.72~5.83 GHz. The proposed antenna is composed of a planar monopole and underneath three by three array arrangement of Jerusalem Cross (JC) structure metasurface. The simulated results show that the integrated antenna express 4.09% and 4.14% impendence bandwidths, increased gain up to 7.9 dB and 8.2 dB, front to back (FB) ratio achieved to 20 dB and 18 dB at the two frequencies, respectively. The measured results agree well with simulations. In addition, the metasurface not only is equivalent to a ground plane for isolation, but also acts as the main radiator, which enables a great reduction in the specific absorption rate (SAR). Furthermore, because of a compact solution, the proposed integrated antenna can be a promising device for various wearable systems.

A maximum a posteriori (MAP) approach, based on the Bayesian criterion, is proposed to overcome the low cross-range resolution problem in forward-looking imaging. We adapt scanning radar system to record received data and exploit deconvolution method to enhance the real-aperture resolution because the received echo is the convolution of target scattering coefficient and antenna pattern. The Generalized Gaussian distribution is considered as the prior information of target scattering coefficient in MAP approach for the reason that it could express different target scattering coefficient properties with the control of statistic parameter. This constraint term makes the proposed algorithm useful in different applications. On the other hand, the reconstruction problem can also be viewed as the l_p-norm (0 < p ≤ 2) regularization. Simulation results show the robustness of the proposed algorithm against additive noise compared with other superresolution methods.

In this paper, the robust optimization shape and drive of switched reluctance motors (SRM) are discussed using robust particle swarm optimization (RPSO). The shape optimum goal of the algorithm was found for maximum torque value and minimum torque ripple, following changing the geometric parameters. The drive optimum aim of the algorithm was found minimum torque ripple, following changing the current profiles. The optimization process was carried out using a combination of RPSO and Finite Element Method (FEM). Fitness value was calculated by FEM analysis using COMSOL4.2, and the RPSO was realized by MATLAB 2011. The proposed method has been applied to two case studies and also compared with seeker optimization algorithm. The results show that the optimized SRM using RPSO has higher torque value, lower torque ripple and higher robustness, indicating the validity of this methodology for SRM design and implementation.

Magnetic Induction Tomography (MIT) is a newly developing technique of electrical tomography that in principle is able to map the electrical conductivity distribution in the volume of objects. The image reconstruction problem in MIT is similar to electrical impedance tomography (EIT) in the sense that both seek to recover the conductivity map, but differ remarkably in the fact that data being inverted in MIT is derived from induction theory and related sources of noise are different. Progress in MIT image reconstruction is still limited, and so far mainly linear algorithms have been implemented. In difference imaging, step inversion was demonstrated for recovering perturbations within conductive media, but at the cost of producing qualitative images, whilst in absolute imaging, linear iterative algorithms have mostly been employed but mainly offering encouraging results for imaging isolated high conductive targets. In this paper, we investigate the possibility of absolute imaging in 3D MIT within a target for low conductivity application (σ < 5 Sm^-1). For this class of problems, the MIT image reconstruction exhibits non-linearity and ill-posedness that cannot be treated with linear algorithms. We propose to implement for the first time in MIT two effective inversion methods known in non-linear optimization as Levenberg Marquardt (LMM) and Powell's Dog Leg (PDLM) methods. These methods employ damping and trust region techniques for controlling convergence and improving minimization of the objective function. An adaptive version of Gauss Newton is also presented (AGNM), which implements a damping mechanism to the regularization parameter. Here, the level of penalty is varied during the iterative process. As a comparison between the methods, different criteria are examined from image reconstructions using the LMM, PDLM and AGNM. For test examples, volumetric image reconstruction of a perturbation within homogeneous cylindrical background is considered. For inversion, an independent finite element FEM software package Maxwell by Ansys is employed to generate simulated data using a model of a 16 channel MIT system. Numerical results are employed to show different performance characteristics between the methods based on convergence, stability and sensitivity to the choice of the regularization parameter. To demonstrate the effect of scalability of absolute imaging in MIT for more realistic problems, a human head model with an internal anomaly is used to produce reconstructions for different finer resolutions. AGNM is adopted here and employs the Krylov subspace method to replace the computationally demanding direct inversion of the regularized Hessian.

A low-profile dual-polarized omnidirectional antenna is presented. The antenna is a combination of a vertically-polarized (VP) antenna and a horizontally-polarized (HP) antenna. The VP antenna is composed of a circular ground plane, a cross-shaped metal patch with four shorted legs and a top-loading circular ring. The printed dipoles of the HP antenna are fed through a three-way power divider etched on an FR4 substrate. To maintain stable radiation and reflection characteristics, the HP feed coaxial cable is soldered on one patch of the VP antenna to reduce the parasitic current on the feed cable. The VP antenna covers the frequency bands for GSM/2G/3G/4G LTE, and the HP antenna works in an overlapping frequency bands for 3G and TD LTE communication systems with high isolation. The VP antenna achieves a wide bandwidth of 108% from 800 MHz to 2700 MHz, and its gains are larger than 2 dBi in 800~960 MHz band and greater than 4 dBi in 1710~2700 MHz band, respectively. The HP antenna works in the frequency band from 1700 MHz to 2700 MHz, and its gains are greater than 3 dBi. The proposed dual-polarized antenna is simulated, fabricated and measured. Measured results are in good agreement with the simulated ones.

Dispersion characteristics of four types of superconducting nanowire single photon detectors, nano-cavity-array- (NCA-), nano-cavity-deflector-array- (NCDA-), nano-cavity-double-deflector-array- (NCDDA-) and nano-cavity-trench-array- (NCTA-) integrated (I-A-SNSPDs) devices was optimized in three periodicity intervals commensurate with half-, three-quarter- and one SPP wavelength. The optimal congurations capable of maximizing NbN absorptance correspond to periodicity-dependent tilting in S-orientation (90˚ azimuthal orientation). In NCAI-A-SNSPDs absorptance maxima are reached at the plasmonic Brewster angle (PBA) due to light tunneling. The absorptance maximum is attained in a wide plasmonic-pass-band in NCDAI_1/2*λ-A, inside a flat-plasmonic-pass-band in NCDAI_3/4*λ-A and inside a narrow plasmonic-band in NCDAI_λ-A. In NCDDAI_1/2*λ-A bands of strongly coupled cavity and plasmonic modes cross, in NCDDAI_3/4*λ-A an inverted-plasmonic-band-gap develops, while in NCDDAI_λ-A a narrow plasmonic-pass-band appears inside an inverted-minigap. The absorptance maximum is achieved in NCTAI_1/2*λ-A inside a plasmonic-pass-band, in NCTAI_3/4*λ-A at inverted-plasmonic-band-gap center, while in NCTAI_λ-A inside an inverted-minigap. The highest 95.05% absorptance is attained at perpendicular incidence onto NCTAI_λ-A. Quarter-wavelength type cavity modes contribute to the near-field enhancement around NbN segments except in NCDAI_λ-A and NCDDAI_3/4*λ-A. The polarization contrast is moderate in NCAIA-SNSPDs (~10²). NCDAI- and NCDDAI-A-SNSPDs make possible to attain considerably large polarization contrast (~10²-10³ and ~10³~10⁴), while NCTAI-A-SNSPDs exhibit a weak polarization selectivity (~10-10²).

A compact 2×2 dual-band MIMO antenna is proposed with polarization diversity technique for present wireless applications. The proposed design combines the horizontally and vertically polarized radiating elements. The effect of mutual coupling between radiating elements is reduced by partially stepped ground (PSG) and by the orthogonal placement of antenna elements. The whole configuration is designed over a substrate of size 70×70 mm². The measured frequency bands extend from 2.408-2.776 GHz, and 4.96-5.64 GHz frequencies with SWR < 2. The measured isolation is more than 21 dB between adjacent and diagonal ports. The measured peak gains at 2.54 GHz, and 5.26 GHz resonant frequencies are 3.98 dBi and 4.13 dBi, respectively. The designed MIMO covers LTE bands (7/38/41), WLAN bands (2.4/5.2/5.5 GHz), and WiMAX band (2.5 GHz). The diversity performances in terms of peak gain, MEG, ECC, and directivity have also been reported.

Flexible substrates have been increasingly studied in recent years. This paper proposes natural rubber as a new substrate material for flexible antennas. In our work, prototype antennas were built using rubber formulated with different filler contents. Carbon black was used as the filler where its amount was varied to yield different dielectric properties. Prototype inset-feed microstrip patch antennas with outer dimensions 7.52 mm × 10.607 mm × 1.7 mm and copper as its conducting material were fabricated to operate at 2.45 GHz. The prototypes were measured and their performance analyzed in terms of the effects of filler content on Q, return loss and bending effects on their gain and radiation characteristics. The return loss and gain were found to be comparable to those built on existing synthetic substrates, but these new antennas offer an added feature of frequency-tunability by varying the filler content. Under bending conditions, these new antennas were also found to perform better than existing designs, showing less changes in their gain, frequency shift and beamwidth, in addition to less impedance mismatch when bent.

This paper presents a miniaturized ultra wideband (UWB) antenna with metamaterial for WLAN and WiMax applications. For miniaturization of UWB antenna resonating 3.1-10.6 is designed Ghz using fractalization of the radiating edge and slotted ground structure approach. A miniaturization of active patch area and antenna volume is achieved up to 63.48% and 42.24% respectively, with respect to the conventional monopole UWB antenna. This antenna achieves a 143% impedance bandwidth covering the frequency band from 2.54 GHz to 15.36 GHz under simulation and 132% (2.95-14.28 GHz) in measurement. The electrical dimension of this antenna is 0.32
× 0.32
(38mm × 38mm) at lower frequency of 2.54 GHz. As per IEEE 802.11a/b/g and IEEE 802.16e standards, WLAN (2.4 -2.5 GHz, 5.150 -5.250 GHz, 5.725 -5.825 GHz), WiMAX (3.3-3.8 GHz) bands are achieved by using slotted ground structure and metamaterial rectangular split ring resonator. The proposed antenna is fabricated on FR4 substrate of thickness 1.6 mm and a dielectric constant 4.3 and tested. The proposed antenna yields a −10 dB impedance bandwidth of about 11.1% (2.39-2.67 GHz), 59.1% (2.87-5.28 GHz) and 7.4% (5.58-6.01 GHz) under simulation and 4.5% (2.41-2.52 GHz), 51.1% (3.12-5.26 GHz) and 3.8% (5.69-5.91 GHz) in measurement for 2.4, 3.5 & 5 and 5.8 GHz bands respectively. Stable radiation patterns with low cross polarization, high average antenna gain of 3.02 dBi under simulation and 2.14 dBi in measurement and measured peak average radiation efficiency of 76.6% are observed for the operating bands. Experimental results seem in good agreement with the simulated ones of the proposed antenna.

This paper proposes two rectangular ring planar monopole antennas for wideband and ultra-wideband applications. Simple planar rectangular rings are used to design the planar antennas. These rectangular rings are designed in a way to achieve the wideband operations. The operating frequency band ranges from 1.85 GHz to 4.95 GHz and 3.12 GHz to 14.15 GHz. The gain varies from 1.83 dBi to 2.89 dBi for rectangular ring wideband antenna and 1.89 dBi to 5.2 dBi for rectangular ring ultra-wideband antenna. The design approach and the results are discussed.

In the paper, we prove two theorems relating to the theory of thin impedance vibrator radiators excited by a lumped voltage generator under rather general conditions. The first theorem proves that influence of external electrodynamic media on the vibrator current distribution is limited and can be estimated using a small natural parameter. The second theorem ascertains that there exists principal possibility to compensate influence of spatial boundaries upon current distributions on a perfectly conductive vibrator by applying to its surface complex impedance with predetermined variation along the vibrator length. Several corollaries disclose a range of the theorems application and their fundamental importance.

The authors present transmission data, taken at Ka (36 GHz) and W (95 GHz) bands in the millimetre-wave region of the electromagnetic spectrum, for various dressing materials used in the treatment and management of burn wounds. The results show that such materials are highly transparent (typically > 90% transmission) and, in their dry state, will permit the sensing of the surface of the skin through the thick layers (> 2 cm) of different dressings typically applied in medical treatment of burn wounds. Furthermore, the authors present emissivity data, taken at the same frequency bands, for different regions of human skin on the arm and for samples of chicken flesh with and without skin and before and after localised heat treatment. In vivo human skin has a lower emissivity than chicken flesh samples, 0.3-0.5 compared to 0.6-0.7. However, changes in surface emissivity of chicken samples caused by the short-term application of heat are observable through dressing materials, indicating the feasibility of a millimetre-wave imaging to map changes in tissue emissivity for monitoring the state of burn wounds (and possibly other wounds) non-invasively and without necessitating the removal of the wound dressings.