An internal dual-band flexible antenna is described. The antenna employs a rectangular patch to improve the interrogation range (above 100 mm) for near-field communications (NFC), as well as the passive average gain performance (above -20 dBi) for FM radio. A preliminary prototype antenna exhibits an interrogation range of 110 mm at 13.56 MHz and a passive average gain performance from -15.6 to -13.5 dBi in the range 86-108 MHz, while demonstrating an omnidirectional radiation pattern for FM radio applications.

Nowadays the mobile personal communication systems and wireless networks are commonly used. Experience has revealed that the antennas suitable for these applications should have small size and operate in assigned different frequency bands. For this purpose, circularly polarized (CP) multi-band square microstrip antenna with three N-slots and a pair of truncated corners is proposed, designed and simulated. To reduce the losses and improve the antenna efficiency in addition to the bandwidth, an efficient electromagnetic band gap (EBG) structure is introduced. The proposed antenna has produced a higher efficiency, an improved operational bandwidth, and a higher gain relative to the conventional microstrip antenna.

The configuration of a new circularly polarized microstrip antenna with omnidirectional radiation pattern for GPS-L1 application is proposed in this paper. The designed antenna has a back-to-back rectangular-patch structure, and two patches are fed by coaxial cable connected with a Wilkinson power divider. The horizontal omnidirectional radiation pattern was achieved by both simulation and measurement. Axial ratio in the peak gain plane was around 3 dB ranging from 1.5 dB to 3.6 dB. The variation of RHCP gain in the horizontal omnidirectional circular polarization plane was smaller than ±1 dBic. And peak RHCP gain of the designed antenna was about 2.3 dBic.

Use of discontinuities in microstrip lines is currently employed to improve the performance of different passive circuits, including reduction of amplifiers, enhancement of filter characteristics and applications to suppress harmonics in patch antennas. This paper presents an improved method of size reduction of a microstrip antenna using Defected Microstrip Structure (DMS) that it is used to perform serious LC resonance property in certain frequency. The DMS is integrated in antenna structure, and therefore this method keeps the antenna size unchanged and makes a resonance frequency. This resonance is due to the abrupt change of current path of antenna that resonates at 5.8 GHz which is shifted to 2.69 GHz thanks to spiral DMS. A prototype of the antenna was fabricated with an FR4 substrate and tested.

The electromagnetic field equations are solved to give the 4-potential in Hermite-Gaussian beams as a function of both the 4-positions of the beam waist and each point in the field. These solutions are the sums of products of position-dependent complex 4-vectors and modified Bateman-Hillion functions. It is assumed that the time difference between the beam waist and each other point is equal to the distance between the points divided by the speed of light. This method is shown to generate solutions that preserve their forms under Lorentz transformations that also correspond to the well known paraxial solutions for the case of nearly parallel beams.

The deflection of charged particle beams by electric and/or magnetic fields is invariably based on the field centred approach associated with Maxwell-Lorentz and incorporated into the Lorentz force formula. Here we present an alternative method of calculation based on the force formula of Weber-Ritz and which does not involve, directly, the field entities E and B. In this study we evaluate the deflection of an electron beam by a long solenoid carrying direct current and positioned centrally across the beam. The experiment has some bearing on the Aharonov-Bohm effect in that our calculations indicate that even for very long solenoids the classical force on the beam remains finite. The standard interpretation of the effect is, however, in terms of quantum mechanics and vector potential. Experimental measurements have been made of electron beam deflections by three solenoids, 0.25 m, 0.50 m and 0.75 m long; each solenoid is doubly wound with the same winding density (2600 turns per metre) and carrying the same current of 5.00 A d.c. Our results indicate that, within the limits of experimental error, both Weber-Ritz and Maxwell-Lorentz theories correlate with measurements for the longer solenoids. However in the case of the shortest solenoid, the lack of uniformity of the magnetic field, leads to significant error in the calculation of beam deflection by the Lorentz force. By contrast in a Weber-Ritz calculation a precise value of beam deflection is obtained by equating the impulse of the non uniform beam force to the vertical momentum change of the electron. This is a fundamentally different approach which uses a statistical summation of forces on the beam in terms of relative velocities between moving electrons and involves a direct computation of the vertical force on the beam due to the circling solenoid current. This method has distinct advantages in terms of economy; that is, it does not involve directly field entities E and B, nor the leakage flux from the solenoid or the vector potential.

Nowadays new safety related systems design include electromagnetic analysis (EMA) during their development. Each of these systems is composed by smaller apparatuses that contain electronic components able to emit electromagnetic (EM) waves. On the other hand, the usage of smaller integrated circuit increase their susceptibility to EM interference. Companies often underestimate the importance of emissions lower than standard limits. A method based on near-field (NF) to far-field (FF) transformation is introduced in order to evaluate radiated emission leakage. This study is an important novelty to analyze electromagnetic issues in the case of safety related systems. Moreover, authors presented how this method is positioned as to current standards. Effectively NF-FF is proposed for site survey analysis on assembled systems where EM leakages should be mitigated to avoid EM attacks. Tools and measurements presented here can be used to sketch the virtual EM (VEM) interface of device-under-test (DUT) in terms of emissions amplitude, frequency and direction. An opponent could use this information to jam these systems utilizing an attack model based on a circular antenna here presented. The results indicate that it is feasible to use this methodology to analyze EM radiated emissions starting from NF information. Compared with current immunity test levels, the EM attack planned on VEM interface characteristics can be deemed efficiently against safety related systems.

A new miniaturization methodology suitable for printed linear antennas is presented. Miniaturization is accomplished by replacing a linear radiator element of a conventional antenna with a compact continuously varying-impedance profile governed by a truncated Fourier series. A design example of a printed half-wavelength dipole antenna is designed and realized in microstrip technology. The performance of the proposed antenna is compared with its equivalent uniform dipole to highlight the performance equivalency. With a 25% reduction in the dipole arm length, both antennas show a measured peak gain and a fractional bandwidth of 5.4 dBi and 16%, respectively at 2.5 GHz; hence, the overall electrical performance is preserved. It will be shown that the design procedure is systematic and accurate. The proposed approach has potential for achieving advanced frequency characteristics, such as broad- and multi-band antenna responses.

Graphene is increasingly being used in the design of electromagnetic devices. The resistivity of graphene can be adjusted via chemical potential tuning, which truly benefits the implementation of tunable and reconfigurable devices. This paper investigates the switch-like attribute of parasitic graphene surface used in a dipole operating at 0.39 THz. Further, a novel orbital angular moment (OAM) generator with radiation reconfiguration is proposed. Spiral beams carrying variety of OAM modes can be produced easily using the generator.

The electromagnetic force acting on a Rayleigh particle placed in a rectangular waveguide is studied. The particle is excited using the lowest order TE₁₀ mode. It is determined that the particle is laterally trapped at the high intensity region of the electric field and either pushed away from or pulled toward the light source. This push-pull phenomenon depends on whether the frequency of the light wave is above or below the cutoff frequency (i.e. the particle can be pushed or pulled by tuning the frequency). While conventional optical tweezers rely on a balance of scattering and gradient force in the propagation direction, the phenomenon predicted here switches between the two forces near the lowest cutoff in a waveguide.

In this paper, three commonly used on-ground antenna types (loop, monopole and planar inverted-F antenna) are compared in the scope of wireless body area networks (WBAN) for on-body communications at 2.45 GHz. The bandwidth of the antennas can be enhanced by placing them towards the edge or the corner of the small ground plane (25 × 35 mm²) which has, as a consequence, detrimental effects on radiation characteristics that motivates the examination of the impact of feeding location for on-body propagation in detail. The present study quantifies the trade-off between on-body efficiency, the gain in the direction tangential to the surface, applicability to launch creeping waves and bandwidth potential of the different antenna types with various feeding locations. The simulated channel gain |S₁₁| around tissue-equivalent numerical phantoms is compared to an analytical WBAN path loss model.

This work addresses the low-pass equivalent behavioral modeling of radio frequency (RF) power amplifiers (PAs) for modern wireless communication systems. Similar to a previous approach, here the PA behavioral modeling is based on two independent real-valued feed-forward artificial neural networks (ANNs). A careful analysis is first presented to show that the nonlinear training algorithm for the previous ANN-based approach can be easily trapped into local minima, especially for the ANN that estimates the polar angle component of a complex-valued signal. Then, a modified ANNbased model is proposed to eliminate the local minimum problem, in this way significantly improving the modeling accuracy. Indeed, in the proposed model the two real-valued ANNs are responsible for estimating the in-phase and quadrature components of a complex-valued base-band signal. When applied to the behavioral modeling of a GaN HEMT class AB PA, the proposed ANN-based model reduces normalized mean-square error (NMSE) by up to 2.2 dB, in comparison with the previous ANN-based model having an equal number of network parameters.

In this paper a compact planar dual-mode metamaterial (MTM) antenna using rectangular type complementary split ring resonator (CSRR) is proposed. It is observed that an increase in series capacitance tends to decrease resonant frequency at which n = 1 mode is obtained in the proposed antenna. Zeroth order mode (ZOR) is obtained by means of rectangular type CSRR, tends to provide the miniaturized area. Dispersion relations are shown in order to characterize the metamaterial behavior by extracting the equivalent circuit parameters. The resonant frequency of the antenna is 2.14 GHz with input reflection coefficient up to -45 dB. The electrical size of the proposed MTM antenna is 0.321λ₀ × 0.285λ₀ × 0.011λ₀. ZOR mode is observed at 1.15 GHz although the proposed antenna is operated at 2.14 GHz. Furthermore, it achieves simulated antenna gain of 2.60 dB with 70% radiation efficiency. In order to verify the simulation results of antenna, a prototype is fabricated and measured.

In the paper presented here the optimization of Halbach arrays as storage media for mechanical potential energy is investigated with numerical simulations using FEMM and analytical calculations using the Maxwell stress tensor. Two opposing Halbach arrays form a ``magnetic spring'' and mechanical potential energy is stored when this structure is compressed. It is here seen that the wavelength of the magnetization in the material and the dimensions greatly in fluence the stored energy density. A clear region of maximum is identified which leads to important conclusions on how the material should be employed. The suggested approach for storing energy have advantages and approximately 250 kJ/m³ can be reached. The main drawback is the large prize of rare earth metals such as Neodymium.

A novel planar dual-band microstrip power divider is proposed in this paper. The circuit is composed of two sections of transmission line, short-circuited stub line and planar resistor, which can provide high isolation and good amplitude balance simultaneously at two frequencies. The closed-form equations are derived,and the design procedures of dual-band power divider are given. To Certify the validity, a proposed power divider was fabricated and measured at 950 MHz and 2200 MHz which might be applied to M and CDMA systems. Both theoretical and simulated results are given, which are in good agreement with the measured results.

In this paper, we propose a new retrieval technique to estimate the dielectric permittivity of the sub-soil materials of a stratified structure. The core of the retrieval procedure is a proper electromagnetic circuit model representing the realistic stratified media as a cascade of transmission line segments. Exploiting the analogies between the electrical parameters of the transmission line segments and the constitutive parameters of the materials of the multilayer structure, the propagation of the Ground Penetrating Radar (GPR) signal is equivalently represented as a pair of voltage and current waves propagating in the transmission line network. The effectiveness of the proposed retrieval technique is confirmed by proper experimental results. In particular, the retrieved electromagnetic parameters of the sub-soil materials are found to be consistent with the ones obtained by a direct characterization of the same materials. These results suggest that the proposed method can be successfully applied to the material characterization able to monitor several macroscopic properties of sub-soil materials.

A novel dual-band bandpass filter based on shorted rectangular patch resonator is proposed and experimentally studied. The resonant modes and frequencies of the shorted rectangular patch resonator are analyzed. Based on miniature structure of the new resonator, a novel dual-band bandpass filter with good out-of-band performance is designed for demonstration. The experimental results agree well with numerical simulations.

A broadband artificial material based on meander-line (ML) structures is proposed for enhancing the gain of printed end-fire antennas. The ML based material with an effective index of refraction greater than 1 behaves as a dielectric lens in improving the directivity of an end-fire antenna. The electric field intensity distribution can be changed by the material, resulting in a more directional emission. Simulated results indicate extending the length or width of the material can lead to more significant gain enhancement without destroying the impedance bandwidth of the antenna. Three printed end-fire antennas with and without material loading are fabricated and measured. The measurements show that end-fire antennas loaded with two and four rows of ML structures can obtain gain increments of 0.6-3.6 dB and 1.2-5.7 dB, respectively, and that the radiation patterns are narrowed in both E- and H-planes over the whole operating band (6-11.5 GHz).

The present paper analyses and documents the merits of incorporating fractal design in microstrip antenna intended to be mounted on and integrated into the design of smart vehicles. A novel design is proposed for a compact tri-band hexagonal microstrip antenna to be integrated with the body of a smart vehicle for short range communication purpose in an Intelligent Transport System (ITS). This antenna can be used at 1.575 GHz of GPS L1 band for vehicle to roadside communication, at 3.71 GHz of mobile WiMAX band (IEEE 802.16e-2005) for blind spot detection and at 5.9 GHz of DSRC band (IEEE 802.11p) for vehicle to vehicle communication. At 3.71 GHz, the two major lobes of the antenna radiation beam, tilted by 35° on both sides from its broadside direction, help the vehicle to detect blind spots efficiently. The largest dimension of the proposed antenna corresponds to the lowest resonating frequency, 1.575 GHz. Compared to the conventional hexagonal patch, the modified Sierpinski fractal proposed herein reduces the overall area, at 1.575 GHz, by 75%, with 5.2 dBi gain. In comparison with other popular fractals, the proposed fractal structure achieves demonstrably better antenna miniaturization. When the antenna is mounted on the vehicle, considered an electromagnetically larger object, the simulated and on-vehicle experimental results show antenna gains of more than 5.5 dBi at 1.575 GHz, 8 dBi at 3.71 GHz and 9 dBi at 5.9 GHz in the desired direction with negligible amount of electromagnetic interference inside the car.

A novel 180˚ out-of-phase power divider with complex-source to complex-load impedance transformation and high power-handling capability is proposed in this paper. It is composed of three double-sided parallel-strip lines (DSPSLs), a conduct plane in the middle as common ground, and two resistors for heat sinking and high isolation. Based on the rigorous odd- and even-mode analytical methods, closed-form design equations about electrical parameters are obtained. To demonstrate our design theory, a practical three-layer out-of-phase power divider is designed, simulated and measured. The measured results show that the return losses |S_ii| (i=1, 2, and 3) are all larger than 17 dB. The insertion loss |S₂₁| (|S₃₁|) is 3.6 dB (3.7 dB). The isolation |S₂₃| is -24 dB, and the output phase difference is -177˚ at the operating frequency. Good agreements between the simulated and measured results verify our design theory.