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.

Laser technology has been promoting various microscopy methods and thus making great progresses in life science. Further than contribution to ``seeing is believing'', lasers have also demonstrated their capacity of manipulating cells and even molecular signaling. Specifically, with advances of lasers and combination with other techniques, recent reports show that cell calcium ion, a universal intra- and inter-cellular messenger, can be modulated by lasers at different levels of biological organization from organelle to tissue. It is very encouraging that laser irradiation can activate or control plenty of corresponding cell processes and functions by regulating cell calcium signaling pathways, with promising potential in both scientific research and clinical application. In this paper, optical techniques for regulation of cell calcium signaling are specifically reviewed. Most methods need exogenouschemicals or genetic materials to convert incident photon into stimulation that cells can response with specific molecular dynamics. The only all-optical approach is achieved by nonlinear excitation with femtosecond laser, despite lack of specificity and controllability, providing possibility of a totally noninvasive method without any biochemical materials and thus further potential clinical application in human beings. The developments and techniques of those methods are introduced and explained, with analysis on their properties and current challenges. Potential applications and prospective development are also discussed. Researchers on biophotonics and related biological fields can benefit from this review. It also provides a systematic reference to doctors and researchers who are working on practical application of those methods.

Canonical solutions to frequency domain Maxwell's equations in the spherical coordinate system have found extensive use in the scientific literature. What is conspicuous by its absence is lack of such expressions for transient Maxwell systems. The existence of such expressions or approximations provide the means to glean interesting physics as well as validate existing numerical fullwave solvers. However, developing such expressions is beset with challenges; direct inverse Fourier transforms of frequency domain expressions are unstable. Successful approaches that ameliorate this instability are more recent endeavor. In this paper, we generalize our earlier contribution to this effort by exploiting a novel representation of the retarded potential to derive expressions for scattering from a dielectric sphere. Several results are provided that demonstrate the stability and accuracy of the method.

In this contribution, the On-body propagation measurements at 40 m underground mine gallery and their statistical analysis are presented. Monopole antennas were installed on the body in order to form three on-body channels, namely belt-chest, belt-wrist and belt-head. The channel parameters of a 2 × 2 Multiple-Input Multiple-Output (MIMO) On-body system are evaluated and compared to the single-input single-output (SISO) system parameters. It was shown that the RMS delay spread and capacity values of the MIMO channels are higher than those of the SISO channels. The average value of the Ricean K-factor shows little difference between the MIMO and SISO belt-chest measurements. The calculated capacity values for a constant signal to noise ratio (SNR) and those calculated at a constant transmitted power demonstrate that the propagation performance is significantly improved by using the MIMO compared to the conventional SISO scheme. Hence, MIMO technology is a suitable candidate for On-body underground communications.

This paper diagnosis the effect of the AC current densities induced by the electromagnetic interference between high voltage power line and buried power line on the cathodic protection performance of the X70 steel in simulated soil. First, the induced AC voltage onto the pipeline was calculated for different power line configuration, separation distances between transmission line and pipeline and parallelism lengths. The induced AC current density was calculated function to the induced AC voltage, soil resistivity, and holiday diameter. Then, the electrochemical characters of the X70 steel at various AC current densities are measured using the potentiodynamic method. The electrochemical parameters obtained by the electrochemical tests are used as boundary conditions in the cathodic protection simulation model. The results indicate that, under influence of AC current densities, the X70 steel is more susceptible to corrosion, and the cathodic protection is unable to maintain the protection potential.

The properties of the Finite Olver-Gaussian beams propagating through an uniaxial crystal orthogonal to the optical axis are studied. An analytical expression is developed, and some numerical simulations are performed to investigate the effects of some parameters on intensity distribution and profile of this beams family at the out-put plane of the uniaxial crystal. The results show that the beam exiting the optical system depends on the ratio of the extraordinary refractive index to the ordinary refractive index. Upon propagation in the uniaxial crystal, the Finite Olver-Gaussian beam in two transversal directions accelerates, while the acceleration in the transversal direction orthogonal to the optical axis is far slower than that in the transversal direction along the optical axis.

Three horizontally-polarized (HP) omnidirectional antennas are proposed and discussed in this paper. The antennas are composed of 3, 4 or 5 printed dipoles with corresponding wideband 3-, 4- or 5-way feeding networks. The feeding networks are simple in structure and easy to be matched with the printed dipoles. All of the proposed antennas operate in the frequency band of 1.7-2.7 GHz, covering the DCS1800, WiFi2700 and 4G-LTE bands with reflection coefficients less than -15 dB. Effects of the number of the printed dipoles on omnidirectional characteristics are discussed. Crossed strips are applied to improve their cross-polarization performance. The proposed antennas are simulated, fabricated and measured. Both simulated and measured cross-polarization levels are lower than -15 dB from θ=60° to θ=120° conical cuts. The antennas demonstrate good omnidirectional patterns in the whole frequency band, which can be widely used for indoor 4G-LTE indoor distributed antenna system (DAS) applications.

For the radiation problem of multi-antenna on electrical-large platform, a multi-region MoM-PO (Multi-MoM-PO) is firstly proposed in this paper. The conventional MoM-PO generally treats all the antennas as a whole MoM region, but in the Multi-MoM-PO, each antenna is classified as one MoM region. On the basis of the mutual interaction between each MoM region and PO region, the self-interactions among MoM regions are considered. Numerical examples demonstrate that the multi-region technique can effectively boost the efficiency of impedance matrix filling compared with the conventional MoM-PO. Finally, the dependence of the filling efficiency against the number of antennas on platform is discussed.

Magnetic induction tomography (MIT) is a non-invasive medical imaging technique with promising applications such as brain imaging and cryosurgery monitoring. Despite its potential, the realisation of medical MIT application is challenging. The computational complexity of both the forward and inverse problems, and specific MIT hardware design are the major limitations for the development of MIT research in medical imaging. The MIT forward modeling and linear system equations for large scale matrices are computationally expensive. This paper presents the implementation of GPU (graphics processing unit) for both forward and inverse problems in MIT research. For a given MIT mesh geometry composed of 167,488 tetrahedral elements, the GPU accelerated Biot-Savart Law for solving the free space magnetic field and magnetic vector potential is proved to be over 200 times faster compared to the time consumption of a CPU (central processing unit). The linear system equation arising from the forward and inverse problem, can also be accelerated using GPU. Both simulations and experimental results are presented based on a new GPU implementation. Laboratory experimental results are shown for a phantom study representing potential cryosurgery monitoring using an MIT system.

The aim of angular super-resolution is to surpass the real-beam resolution. In this paper, a method for forward-looking scanning radar angular super-resolution imaging through a deconvolution method is proposed, which incorporates the prior information of the target's scattering characteristics. We first mathematically formulate the angular super-resolution problem of forward-looking scanning radar as a maximum a posteriori (MAP) estimation task based on the forward model, and convert it to an equivalent unconstrained optimization problem by applying the log-transforms to the posterior probability, which guarantees the solution converges to a global optimum of an associated MAP problem and it is easy to implement. We then implement the unconstrained optimization task in convex optimization framework using an iterative shrinkage method, and the computational complexity of the proposed algorithm is also discussed. Since the anti log-likelihood of the noise distribution and the prior knowledge of the scene are utilized, the proposed method is able to achieve angular super-resolution imaging in forward-looking scanning radar effectively. Numerical simulations and experimental results based on real data are presented to verify that the proposed deconvolution algorithm has better performance in preserving angular super-resolution accuracy and suppressing the noise amplification.

Microwave induced thermo-acoustic tomography (MITAT) is a developing technique for biomedical applications, especially for early breast cancer detection. In this paper, impacts of short microwave pulse on thermo-acoustic (TA) signals are analyzed and verified through some experimental comparisons. In these experiments, short microwave pulses with widths of 10 ns and 500 ns are employed as radiation resources. TA signals generated from a cubic sample are analyzed in both time- and frequency-domain. A trapezoid sample is also performed for experimental comparing. Different from previous literature, the effects of rising edge of radiation microwave pulse have been intensively studied. Experimental results demonstrate that shorter rising edge duration conducts broader bandwidth of TA signal, which give rise to better spatial resolution for tomography imaging.

A novel triple-band filter using triple-mode substrate integrated waveguide (SIW) resonator is presented in this paper. The proposed resonator consists of a square cavity with two additional metallic vias that split the first pair of degenerate modes (TE₂₀₁ and TE₁₀₂) at the diagonal of the cavity. Triple-band response is achieved by TE₁₀₁, TE₂₀₁ and TE₁₀₂. The center frequencies of the first band and the third band can be controlled by appropriately adjusting the location of perturbation vias, while the second band keeps almost unchanged. A two-pole triple-band filter with two transmission zeros utilizing the coupled triple mode cavity resonators is designed and fabricated. The measured results agree very well with the simulated ones.

We deal with the problem of determining the profile of a perfectly conducting rough surface from single-frequency and multistatic data. The two fundamental polarizations are investigated, in a two-dimension scattering configuration. Emitting and receiving antennas are positioned on a probing line some wavelengths above the profile. It is shown how the boundary integral equation method can be adapted to the case where the antenna footprint is much wider that the rough part of the profile. The Newton-Kantorovich iterative inversion process is then performed on these synthetic data. Its accuracy and robustness to additive noise are studied in the context of random rough surfaces with correlation length smaller than the wavelength and slope root mean square up to 0.9.

We develop a semi-analytical approach to calculate the polarizability tensors of an arbitrary scatterer. The approach is based on numerical integration from induced charges and currents on the scatterer. By taking the advantages of the present approach, we calculate the polarizability tensors of any arbitrary scatterer in a homogeneous isotropic medium. This approach, in comparison to other reported approaches, is simple, easily implemented, and does not require spherical harmonic expansion or complicated far-eld calculations. We examine the validity of the approach using several examples and compare the results with other approaches.

Realizations of celestial objects in the laboratory have been a tantalizing subject for human beings over centuries. In this paper, we review some of the interesting cases of realizations of black holes in the laboratory. We first review the recent progress in observed black holes realized through the isotropic coordinate transformation method, then discuss the realization of optical attractors. Finally, the Rindler space-time, as a one-dimensional black hole, by using the hyperbolic metamaterials, is discussed.

It is known that slabs of wire media - dense arrays of thin conducting wires - can transport electromagnetic energy of evanescent plane waves over the slab thickness. This phenomenon was successfully used in superlenses and endoscopes. However, in the known configurations the effective energy transfer takes place only at the Fabry-Perot (thickness) resonances of the slab, making broadband power transfer impossible. In this paper we experimentally demonstrate that power transfer by a wire medium slab can be very broadband, whereas the Fabry-Perot resonances are damped, provided that the wires of the wire medium slab extend into the power-emitting body. As a testbed system we have used two rectangular waveguides and demonstrated that a properly designed and positioned wire medium slab transfers modes of any polarization from the input to the output waveguides. This study is relevant to emerging applications where broadband transport of reactive-field energy is required, especially in enhancing and controlling radiative heat flows in thermophotovoltaic systems.