This paper presents a simple analytical model to estimate the radiated field for broadband Power line communication (PLC) or metallic wire structures. In our approach, we avoid to discretize the line and compute the current for each segment (dipole). We consider only near and far end currents and their derivatives (voltages) to express analytically the radiated electromagnetic field. The case of multiple conductor power line is considered with simplified hypothesis: cables are not insulated and the surrounding media is homogenous. The basic electromagnetic equations are formulated and applied to the line to provide analytical expressions able to compute fields in near and far zones which is not usually treated. The main purpose of this paper is to provide an analytical model applied to bare wires corresponding to classical outdoor transmission lines. The advantage of this method is that we do not need to know the current along the line to calculate the radiated fields; therefore, in our study we use only the currents and voltages at the terminations. The calculation time is strongly reduced compared to dipoles conventional method. Results obtained from the proposed closed-form formulation agree with Feko simulation. For indoor configurations, cables are usually insulated and the surrounding media is no more homogeneous; this case is treated with a generalized approach and will be proposed in future paper.

A broadband dual-feed dual-polarized microstrip antenna with low cross polarization and high isolation is presented. The dual-orthogonal linearly polarized mode is excited by two different feed mechanisms from a single circular radiating patch. One of the two modes is excited by a pair of L-shaped probes with a 180° phase differences, and the other is excited by an H-shaped aperture. The proposed design has a very simple antenna structure with a wide input impedance bandwidth (23.25% for Port1 and 35% for Port2) and also its two input port isolation is found to be as low as -40 dB. Measured results of the fabricated antenna prototypes are also carried out to verify the simulation analysis.

Two SPDT switches that have low insertion loss with impedance-transformation networks are presented. The proposed SPDT switches are comprised of two shunt PINs and two quarter-wavelength microstrip lines together with impedance transformation networks, which canceled the capacitance effect at off-state and the inductance effect at on-state simultaneously. The simulated insertion loss performance is less than 0.3 dB and the fabricated ones exhibit on-state low insertion loss of 0.5 dB within the range of 4.6-4.8 GHz.

We study the surface enhanced Raman scattering (SERS) from bimetallic core-shell nanoparticles by taking into account the nonlocal effect. The Gersten-Nitzan model is applied to investigate SERS from a molecule adsorbed on the nonlocal bimetallic nanoparticle. Numerical results show that there are two enhanced SERS peaks for bimetallic coated nanoparticles, and nonlocal effects will lead to less enhancement and blue-shift of SERS peaks. In addition, unusual resonant electric-field patterns are found in the nonlocal gold core in comparison with those in the local case. Our investigation is helpful for understanding some details of SERS schemes in nano-optics and plasmonics when nonlocal effects are considered.

An ultra-wideband (UWB) printed antenna fed by balanced microstrip is proposed. This antenna is in the structure of symmetrical dipoles, each of which consists of 3 semicircular metal patches. The antenna has been simulated by CST MICROWAVE STUDIO^® software and tested. Both the simulation and experimental results indicate that the proposed antenna obtains an ultra-wide bandwidth of 2.8-16.3 GHz, when VSWR is less than 2. The experimental results of the directional diagrams indicate that the proposed antenna acquires a balance feed within the whole working band. The analysis of the surface current on the radiators indicates that the proposed antenna has a radiation mode of standing wave current in low frequency and traveling wave current in high frequency. The length of the antenna on polarization direction is 0.315 times of the maximum working wavelength, which shows that the antenna is well miniaturized.

In this paper, a novel bandwidth reconfigurable bandpass filter is proposed. Based on a varactor loaded tri-mode resonator consisted of one constant odd mode and two independent varactor-tuned even modes, each passband edge of the proposed filter can be freely adjusted. By varying the reverse bias voltage applied to the varactor diode that is connected to the resonator, the bandwidth can be controlled conveniently. The resonant frequencies and Transmission Zeros (TZs) are derived and verified by both theoretical analysis and simulation. Stepped Impedance Resonator (SIR) is introduced to optimize the harmonic suppression. Finally, the measurement of the fabricated filter shows a fractional bandwidth tuning range of 11.4-32.0 % with a center frequency of 1.75 GHz, a quite low insertion loss of 0.4-1.1 dB, and wideband harmonic suppression up to 6 GHz. The measurement and simulated results show good agreement.

The application of the finite-difference time-domain method with rectangular periodic boundary conditions to the analysis of a hexagonal photonic crystal results in a folded bandgap diagram. The aim of this paper is to introduce a new unfolding method, which allows unambiguously determining the position of the modes in a wave-vector space by taking the advantage of the fast Fourier transform of modal field distributions. Unlike alternative solutions, it does not require any modifications of the FDTD method and is based solely on the postprocessing of the simulation results. The proposed method can be applied to any non-rectangular lattice types, such as hexagonal, face-centered cubic or body-centered cubic.

Retinal prosthesis system is currently being developed in various places around the world. This system involved data transfer between an implanted antenna inside an eyeball and an external camera that is located just in front of the eyeball. While there are plenty of publications about the stimulating electrodes or the processing unit of the system itself, very limited amount has been published regarding the wireless communication link between the two antennas despite the fact that the electromagnetic wave will propagate through a complex medium in the form of Vitreous Humor. This paper will discuss about the constraints associated with implanting an antenna into an eyeball. An antenna design and simulation was performed with the aid of High Frequency Structure Simulator (HFSS) and its Finite Element Method (FEM) mathematical solver in the operating frequency of 402-405 MHz. The antenna, which was a 4 layer microstrip antenna, was positioned at the centre of a spherical model filled with homogeneous Vitreous Humor material. Antenna performances that include return loss, bandwidth, gain, radiation pattern, and SAR value are analysed and compared against those of other implantable antennas operating in Medical Implant Communication Service (MICS) band. Free space and simulating fluid measurements were also conducted on the fabricated antenna to validate the simulation results. It was concluded that the fabricated antenna was able to produce the similar performance to the simulation results and hence at the same level as the other antennas operating in material with lower dielectric constants and conductivities.

In design phase of naval ships, the effectiveness of RCS reduction means such as shaping, shielding and applying radar absorbing materials is assessed quantitatively via several times of numerical analyses. During the process, in general, the numerical analyses have been carried out only for the static case not considering ship motions in actual ocean environments in spite that ocean waves induce the ship motion of the object naval ship and distort RCS measures. In this study, the dynamic RCS characteristics of the naval ship considering the ocean wave-induced motion have been numerically investigated. For this purpose, a dynamic RCS analysis procedure so called ``quasi-static approach'' has been adopted for considering the time varying ship motion. The results for two types of naval ships, a stealthy and a non-stealthy ship, show that the RCS of the object naval ships could be reduced or increased in mean value by the ship motion due to the ocean wave, compared to the static RCS value, and also the measures are considerably affected by the various parameters, type of object ship, significant wave height and incident angle of ocean wave, and incident angle of radar wave.

In this paper, a compact and high isolation microstrip diplexer is designed for broadband and wireless local area network (WLAN) application, simultaneously. The bandpass filter (BPF) for broadband channel is formed by three-coupled-line structure and two short stubs with different size loaded in 50 feed lines, and the BPF for WLAN channel consists of two coupling quarter-wavelength resonators (QWR) and one open stub loaded in short parallel-coupling feed structure. Multiple transmission zeros can be generated due to their intrinsic characteristics, so the broadband BPF with sharp skirt and wide upper-stopband performance and the WLAN BPF with sharp roll-off and lower-stopband characteristic can be realized. The tapped stub not only can generate transmission zeros to deepen the stopband, but also can connect other BPF as an its part without deterioration of in-band performance. Hence, a compact microstrip diplexer combines of two BPFs without the extra junction matching network. The mutual loading effect approximately equivalent to a coupled short QWR can also generate new transmission zero at the passband edge to improve the isolation. A microstrip diplexer with the 3 dB fractional bandwidth (FBW) of 80% for broadband channel and 5% for WLAN channel is designed and fabricated. Good agreement between the simulated and measured results is observed.

The use of Artificial Magnetic Conductor (AMC) as a reflector in a printed antenna is known to improve the antenna's radiation characteristics. This work investigates the implementation of AMC as a reflector on a wideband planar monopole antenna. The investigation is confined to a basic square unit cell of AMC with four possible variations. The AMC structures are constructed with square cells which have either similar square cells or a Perfect Electric Conductor (PEC) as the back plane. These same structures are also fabricated with vias. The impedance bandwidth, gain and power pattern are simulated and measured over the measured -10 dB impedance bandwidth of 3 GHz to 10 GHz. The outcome of the investigation is that, for the antenna element and AMC structures considered in this study, a gain enhancement of up to 6 dB can be achieved with the AMC structures. In addition, introduction of vias is observed not to influence gain, though it improves cross-polarization levels by 3 dB to 5 dB for AMC constructed of squares backed by PEC.

This paper presents an experimental investigations and analyses of ultra-wideband antenna diversity techniques and their effect on the onbody radio propagation channels. Various diversity-combining techniques are applied to highlight; how the overall system performance may be enhanced. Diversity gain is calculated for five different on-body channels and the impact of variation in the spacing between diversity branch antennas is discussed, with an emphasis on mutual coupling, correlation and power imbalance. Results demonstrate the repeatability and reliability of the analysis with error variations as low as 0.8 dB. The study highlights the significance of diversity techniques for non-line-of-sight propagation scenarios in body-centric wireless communications.

The physiological parameters monitoring of human target are considered to be a meaningful and challenging task in non-line-of-sight (NLOS) scenes such as rescue of trapped survivors in post-disaster. In this paper, a new method based on developed adaptive line enhancer (DALE) is proposed to monitor vital signs via ultra-wideband (UWB) radar with centre frequency of 400 MHz. The validity of this new method is proved by means of two experiments with different positions of human target. The good results demonstrate that this new method can be used for vital sign monitoring including respiration and heartbeat through the obstacle. Furthermore, the motion responses due to respiration and heartbeat in different body positions are also discussed.

The Modified Winding Function Theory (MWFTh), regarded as a very powerful and general theory, has been extensively used for the last 15 years. This paper performs an in-depth review of the mathematical and physical framework on which the MWFTh is based, showing that it is indeed very well suited to analyse machines with small air gaps of arbitrary shape. However, contrary to what is usually stated in the literature, it is also proved that its general formulae fail when applied to large air gaps. This major finding is deduced from two different approaches, both of which are later reinforced by numerical examples. In spite of that, there is an important industrial field (diagnosis techniques of salient-pole synchronous machines eccentricities) in which very good theoretical results are reported by applying the MWFTh to these large air-gap machines. This issue is addressed and clarified in the paper.

Fractal arrays are used to increase the bandwidth of the antenna and to reduce grating lobes. The frequency range from 3.1 to 10.6 GHz is specially allocated for the UWB applications. In this paper, a novel antenna based on fractal concepts for ultra wideband (UWB) applications is analyzed, designed, fabricated and tested. Further the antenna is analyzed using the emerging fractal concepts and transmission line method (TLM). The proposed antenna has a good gain bandwidth with broadside radiation pattern. This design is suitable for 3D IC inter-chip and intra-chip communication, and medical imaging applications. This is called Levy's antenna.

The radar backscatter from complex targets, such as aircrafts and ships, tends to vary rapidly with aspect or time. To describe the radar cross section distribution characteristics of such targets, statistic terms are often used. In this paper, we first give a brief introduction of distribution and lognormal distribution model. And complete form of lognormal distribution is proposed which can be used when ratio of mean to median is less than 1 as stealth targets. The significance of the parameters is discussed in detail aiming to find a characterization standard. As an example, the statistic characteristics of the radar cross section data of a stealth aircraft are analyzed with Swerling 1, 3 distribution, distribution and lognormal distribution. The applicability of the distributions is shown with error-of-fit and test of goodness of fit.

Presently, wireless capsule endoscopy (WCE) is the sole technology for inspecting the human gastrointestinal (GI) tract for diseases painlessly and in a non-invasive way. For the further development of WCE, the main concern is the development of a high-speed telemetry system that is capable of transmitting high-resolution images at a higher frame rate, which is also a concern in the use of conventional endoscopy. A vital task for such a high-speed telemetry system is to be able to determine the path loss and how it varies in a radio channel in order to calculate the proper link budget. The hostile nature of the human body's channel and the complex anatomical structure of the GI tract cause remarkable variations in path loss at different frequencies of the system as well as at capsule locations that have high impacts on the calculation of the link budget. This paper presents the path loss and its variation in terms of system frequency and location of the capsule. Along with the guideline about the optimum system frequency for WCE, we present the difference between the maximum and minimum path loss at different anatomical regions, which is the most important information in the link-margin setup for highly efficient telemetry systems in next-generation capsules. In order to investigate the path loss in the body's channel, a heterogeneous human body model was used, which is more comparable to the human body than a homogenous model. The finite integration technique (FIT) in Computer Simulation Technology's (CST's) Microwave Studio was used in the simulation. The path loss was analyzed in the frequency range of 100 MHz to 2450 MHz. The path loss was found to be saliently lower at frequencies below 900 MHz. The smallest loss was found around the frequency of 450 MHz, where the variation of path loss throughout the GI tract was 29 dB, with a minimum of -9 dB and a maximum of -38 dB. However, at 900 MHz, this variation was observed to be 38 dB, with a minimum of -10 dB and a maximum of -48 dB. For most positions of the capsule, the path loss increased rapidly after 900 MHz, reaching its peak at frequencies in the range of 1800 MHz to 2100 MHz. During examination of the lower esophageal region, the maximum peak observed was -84 dB at a frequency of 1760 MHz. The path loss was comparatively higher during examination of anatomically-complex regions, such as the upper intestine and the lower esophagus as compared to the less complex stomach and upper esophagus areas.

In the received signal strength (RSS) based indoor wireless localization system, RSS measurements are very susceptible to the complex structures and dynamic nature of indoor environments, which will result in the system failure to achieve a high location accuracy. In this paper, we investigate the indoor positioning problem in the existence of RSS variations without prior knowledge about the localization area and without time-consuming off-line surveys. An adaptive sparsity-based localization algorithm is proposed to mitigate the effects of RSS variations. The novel feature of this method is to adjust both the overcomplete basis (a.k.a. dictionary) and the sparse solution using a dictionary learning (DL) technology based on the quadratic programming approach so that the location solution can better match the actual RSS scenario. Moreover, we extend this algorithm to deal with the problem of positioning targets from multiple categories, a novel problem that few works have ever concerned before. Simulation results demonstrate the superiority of the proposed algorithm over some state-of-art environmental-adaptive indoor localization methods.

In this paper, a novel end-loaded quarter-wavelength resonator is investigated for the designs of wideband tunable bandpass filter (BPF) and bandstop filter (BSF). The novelty of the resonator lies in that two varactors are added to the two ends of the resonator, and then its resonant frequency can be bi-directionally tuned. As a result, the theoretical frequency tuning range can be significantly extended to approximately double that of the conventional tunable quarter-wavelength resonator. For demonstration, the proposed resonator is applied to design wideband tunable BPF and BSF. As expected, the tuning ranges are 52.4% and 53.5% for the BSF and BPF, respectively. Good agreement can be observed between the simulated and measured results.

The non-equilibrium electron energy distribution function (EEDF) obtained via solving the Boltzmann equation is introduced into the fluid model, and the effects of the microwave frequency on the EEDF and air breakdown are investigated. Numerical simulations show that the breakdown threshold of the fluid model with the non-equilibrium EEDF agrees well with that of the reported experiments. The microwave frequency plays an important role on the shape of the non-equilibrium EEDF at low pressures. The breakdown time at the low pressures predicted by the Maxwellian EEDF is shorter than that from the non-equilibrium EEDF in low-frequency oscillating fields, while matches the latter in high-frequency oscillating fields.