A frequency reconfigurable antenna suitable for handset is proposed in this research. The antenna structure includes an inverted-L shaped monopole and two meandered shorting strips. A wide high frequency band is excited from the inverted-L shaped strip monopole by direct feeding, and then the low and middle frequency bands are excited from two meandered shorting strips. Furthermore, a PIN switch diode is added at the end of shorting strip1 to implement the frequency reconfigurable property. The antenna was fabricated on an FR4 substrate and with a volume of only 9×50×5 mm³. It can cover the operation bands of LTE700/2300/2500, GSM850/900/1800/1900, UMTS2100, and WLAN2400. The detailed considerations and analyses of the design are studied in this paper.

Communication `blackout' is a big challenge for modern space engineering. In the recent decade, the terahertz (THz) technology is believed to be an effective solution for the `blackout' problem. Many research works about the transmission of THz waves in plasma slabs have been carried out. According to those works, the radio attenuation of THz waves in plasma slabs strongly depends on thickness of the slab, electron density, electron collision frequency and temperature. However, few previous works have paid attention to realistic reentry plasma sheath. In the present paper, a hypersonic fluid model is introduced in order to investigate the structure of the realistic plasma sheath which covers a blunt coned vehicle. The scattering matrix method is employed to study the transmission of THz waves in realistic plasma sheath. According to the present study, the wave frequency, electron density and collision frequency are the most significant factors which determine the attenuation of the THz waves in the plasma sheath. Since the whole plasma sheath is inhomogeneous, to install the antenna at an appropriate position helps mitigate the `blackout'. For the blunt coned reentry vehicle, installing the antenna on the wall close to the bottom is helpful for mitigating the `blackout' problem.

Transformation of space coordinates is a tool to synthesize material properties in view of obtaining a controlled electromagnetic field pattern. Also, substrate-integrated waveguide (SIW) technology can well be exploited to develop microwave and millimeter-wave components. In this paper, by combining these features, high-gain SIW planar lens antennas are proposed. Using the embedded transformation-optics lenses, both narrow beamwidth of 12˚ and low sidelobe levels of -23 dB are achieved for the H-plane radiation patterns by a single antenna. The designed transformation-optics lenses can be realized by drilling spatially varying cylindrical holes in an ordinary dielectric substrate. The E-plane radiation patterns can also be improved through the dielectric slabs in front of the antenna aperture integrated in the same substrate. Therefore, using SIW technology, the lens antennas can be fabricated on a single substrate. An H-plane sectoral horn and a Maxwell-fisheye-based lens antenna are designed using the proposed method. Simulation results confirm the validity of the proposed idea and the advantages of these lens antennas.

This paper proposes a wideband dual-polarized magneto-electric dipole antenna composed of two pairs of vertical shorted patches and two pairs of horizontal double-layered planar dipoles. To achieve dual-polarization radiation, two orthogonal Γ-shaped stepped-impedance strip feed lines are designed to excite the antenna. The regions between the vertical shorted patches are loaded by dielectric materials to reduce the antenna profile. In addition, the antenna is backed with a rectangular cavity-shaped reflector to improve radiation pattern stability and diminish back radiation. Experimental results demonstrate that the proposed antenna has obtained a wide impedance bandwidth of 57.1% from 1.5 to 2.7 GHz and high port isolation of better than 30 dB within the bandwidth. The average antenna gain is about 9.7 dBi with a variation of below ±1.5 dB and the radiation patterns are unidirectional, symmetric with low back radiation, and low cross-polarization radiation across the entire operating band.

In this paper the analysis of the static and dynamic behavior of a non-hysteretic superconductive passive linear bearing is described. The high translational symmetry of the magnetic field seen by the superconductor assures a usable long stroke in the order of several tens of millimeters. The linear bearing in combination with an actuating system for only one degree of freedom can be used for accurate long-stroke precision positioning systems for cryogenic environments with zero hysteresis in the movement. The dynamics of the system is investigated using an integral formulation which transforms the solution of the field equations in the solution of an equivalent electric network. The knowledge of the currents in the equivalent network allows to evaluate all the electromagnetic quantities (fields, forces, eddy currents, ...) in the system. Finally, the coupling with the equation of the rigid body permits to simulate the electro/mechanical behavior of the system with six degree of freedom (6 DOF).

This paper describes the original results obtained in the field of multi-beam annular ring antenna array pattern synthesis for the modes TM11 and TM12, by applying an iterative algorithm for phased arrays, which is able to produce low side-lobe levels patterns with multiple prescribed main lobes. The ring antenna analysis builds on the modified cavity model; this letter permits to take account of the fringing field effects by virtue of the dynamic permittivity. The proposed method is based on the adaptive particle swarm optimization algorithm. This solution is characterized by its simple implementation and a reduced computational time to achieve the desired radiation patterns. These advantages make the presented algorithm suitable for a wide range of communication systems. The original results obtained in the field of antenna array pattern synthesis are presented to illustrate the performance of the proposed method.

This paper presents a systematic design process to design Bandstop Filters from Single-Band (SB-BSF) to Hexa-Band (HB-BSF). The presented BSFs are useful to suppressing the unwanted signal frequencies from 1.98 GHz to 7.75 GHz. Single-Band BSF suppress the frequency 1.98 GHz; Dual-Band BSF suppress 2 GHz and 3.4 GHz (WiMax Band); Triple-Band BSF suppress 2.0 GHz, 3.4 GHz, and 4.75 GHz; Quad-Band BSF suppress 2.0 GHz, 3.4 GHz, 4.75 GHz, and 6.4 GHz; Penta-Band suppress 2.0 GHz, 3.4 GHz, 4.0 GHz, 4.85 GHz, and 6.75 GHz; however Hexa-Band suppress 2.0 GHz, 3.4 GHz, 4.2 GHz, 4.75 GHz, 6.5 GHz, and 7.75 GHz. The attenuation level for the suppressed frequencies varies from 19 dB to 62 dB, and the quality factor varies from 17 to 384.5. The simulated and measured results are presented to validate the design process. Such compact BSFs could be useful in modern communication systems to stop the potential interference of the unwanted signal frequencies in WLAN and UWB bands.

A novel rectangle tree fractal antenna (RTFA) for ultra-wideband(UWB) application with dual band notch characteristics is proposed. The radiating path is the tree fractal structure which is formed by the superposition of a number of rectangular patches, and multi-frequency resonance characteristics are obtained by only increasing the tree fractal iterations. UWB operation(3.1-10.6GHz) is achieved by using defected ground structure(DGS) on the ground plane to improve the impedance characteristics between adjacent resonant frequencies. The dual notch bands characteristics are realized by three U-slot on the tree fractal path and effectively suppress the interferences of WiMAX and WLAN. The measurement and simulation results have an acceptable agreement, and indicate that the antenna is suitable for UWB applications.

In this paper, a simple approach for efficiency enhancement of a wireless power transfer system by using mu near zero (MNZ) type of metamaterial is proposed. A single slab containing one-sided periodic structures of 3×3 array of meander-line unit cell has been placed between transmitting and receiving coils in the wireless power transfer system. The presented metamaterial structure is less complex than other reported metamaterial structures in the area of wireless power transfer system. The simulation and measurement have been performed with and without metamaterial slab. Using metamaterial slab, the maximum efficiency has been obtained about 55.3%, i.e. an improvement of efficiency around 15.7% is obtained compared to a wireless power transfer system without metamaterials. Interestingly, the proposed wireless power transfer system shows a steady improvement of efficiency even if the distance between the transmitting and receiving coil is increased.

We discuss in this paper the stability of the time marching (TM) method. We identify one cause of instability in the method associated with the calculation of variables involved in the convolution operation. We provide a solution to this problem, preventing the appearance of unstable poles in the Z-domain. This solution is fundamentally different from other previously presented approaches in the sense that it is not based on filtering or predictive techniques. Instead, it consists of preprocessing the known variable in the convolution equations.

This paper presents a design of a compact triple-band bandstop filter (BSF) using embedded capacitors. The presented BSF is useful to suppress the signal frequencies 2.2 GHz, 5.53 GHz and 4.15 GHz from the WLAN and UWB band with attenuation level 33.5 dB, 27.6 dB and 24.9 dB, respectively. The quality factors of the three bands are 5.21, 31.92 and 79.0, respectively. The simulated and measured results are presented to validate the concept. Such BSFs could find application in modern communication systems to suppress the potential interference of the unwanted frequencies from the WLAN and UWB band.

This paper is devoted to research of zone-spectra of one-dimension finite-element photonic crystal quartz/silicon in millimeter waveband. It is supposed that holes with dimensions in order of wavelength are fabricated in the silicon slabs. It is shown by the numerical and experimental investigations the possibility of using of effective medium approximation for the silicon element of photonic crystal. The paper introduces the simple phenomenological formula for calculation of effective permittivity of perforated silicon slab.

This paper presents a zeroth order metamaterial substrate integrated waveguide antenna. The antenna is designed to have a compact size based on employing only one composite right/left-handed cell. The antenna resonates at 6.1 GHz with overall radiator size of 14.4 mm × 8 mm² which represents 50% size reduction compared to conventional microstrip antenna operates at the same frequency. The zeroth order mode of the antenna has been verified using both analytical explanation and full wave simulations. Moreover, the full wave simulations in addition to experimental measurements have been employed to demonstrate the antenna resonance and radiation characteristics.

In this paper, a broadband power amplifier with high efficiency and output power based on GaN HEMT is presented. The design of broadband matching network and transistor package modeling is presented, and a simulation strategy is proposed to increase the simulation accuracy. According to measured results, the PA module shows a linear gain of 10~13 dB during 1.9-4 GHz. The efficiency can reach 74.5%, and the maximum output power reaches 33.2 Watt. For a 5-MHz WCDMA signal, the designed power amplifier achieves an average output power above 20 W when ACLR = -30 dBc over the entire working band.

A fast design technique for lumped-element multilayered bandpass filters is proposed. With this technique, the difference between multilayered component values and theoretical component values can be quickly estimated and tuned. The design procedure for filters can be obviously simplified, and the efficiency can be improved. This technique is discussed in detail, and mathematic explanation is given. An example is used to show the entire design procedure. The measurement result agrees well with the desired result, which shows the effectiveness of proposed technique.

In this paper, a compact planar quasi-Yagi antenna with enhanced radiation characteristics is presented. The proposed structure is designed by incorporating metamaterial unit cells in place of conventional directors. Here, the technique used for directivity improvement is that the refractive index of the metamaterial is lower than that of the antenna substrate, which acts as a regular lens for beam focusing. Loading the quasi-Yagi antenna with metamaterial results in directivity as well as gain enhancement at the end-fire direction as compared to the quasi-Yagi antenna with directors. In addition, reduction in the overall size of the proposed quasi-Yagi antenna by 26.67% is achieved. An enhanced impedance bandwidth has also been noticed. The gain performance of the proposed antenna within the frequency band has been studied.

Inductive power transfer is recently a common method for transferring power. This technology is developing as the modern technologies need to get more efficient and updated. The power transfer efficiency has potential to get better. There are different ways to achieve a desirable efficiency. In this paper, a suitable geometry of a coil for transferring power as a transmitting coil is examined. In this work, three types of geometries are designed. Frequency analysis at frequency range (10 kHz-50 kHz) is done to investigate behaviour of various geometries. Magnetic field, electric field, magnetic flux density, and current density for various geometries are presented and compared. Magnetic flux density is measured via an experimental setup and is compared to simulated one to verify the validity of simulation results.

Shear-horizontal (SH) wave is commonly used in monitoring and detecting steel plate structures. Electromagnetic acoustic transducer (EMAT) based on magnetostriction owns higher transducing efficiency and can be applied in non-contact situations. In some practical applications, it is necessary to inspect the structure on a specific direction and the inspecting direction is required to be variable and accurately controllable. This work proposes a novel direction-controllable EMAT for SH0 mode waves based on magnetostriction. Theoretical foundation and analysis on the magnetostriction model of the new EMAT and working parameters determination are conducted. The detailed structure and design of the new EMAT are presented, with the pre-magnetized open annular nickel strap bonded to the steel plate providing the circumferential static bias magnetic field, and the cooperation of embedded conductors in the rotating slider and open metal rings providing the dynamic magnetic field. Besides, the experimental system for the performance verification of the new EMAT is setup. Three indexes, the dead zone angle, focus angle and consistency error are defined to evaluate the performance quantitatively. The dead zone angle of the new EMAT is 28.74°; the focus angle is 10.7°; the consistency error is only 1.4%. Experimental results show that the proposed direction-controllable EMAT is highly directional. The stimulating direction can be accurately controlled, and the circumferential consistency is fairly high. The direction-controllable EMAT can hopefully provide a practical solution for directional monitoring and inspecting for steel plate structures.

With increasing interest in the usage of wearable wireless communication technologies at 1.8 & 2.4 GHz and 5 & 9 GHz band of frequencies, investigations on the human body interaction with these devices are becoming important. This paper provides a microstrip-based multi-band monopole antenna for body Wearable Wireless Devices (WWD), covering licensed and license-free wireless technologies at UHF/UWB when placed on human body. Five parts of the body were considered to evaluate the electromagnetic (EM) effects on the body. Specific Absorption Rate (SAR) values were found to range from 0.09-0.25 W/kg by using numerical modelling. The thermal effects were investigated experimentally using infrared thermography, and temperature changes not exceeding 1˚C were noticed. Analyses of numerical, simulated and experimental results show that infrared thermography, a temperature-based technique, can be used to evaluate the compliance of WWDs with safety exposure limits for various wireless applications.

In this paper, an improved broadband substrate integrated waveguide (SIW) phase shifter with embedded air strips is presented. Phase shifter can be generated based on the variable widths of SIW, variable lengths of microstrip line and a row of embedded air strips. The simulated and measured results both show that this kind of SIW phase shifter has excellent performance for a wider bandwidth. Measured results indicate that the proposed SIW phase shifters for the 45° and 90° versions have achieved the fractional bandwidths of 59.6% from 10.2 to 18.85 GHz with the accuracy of 2.5°, and of 62.3% from 9.5 to 18.1 GHz with the accuracy of 5°, respectively. The return losses are better than 15.8 dB and 14.5 dB for 45° and 90° modules, respectively. In addition, the insertion losses are both found to be better than 1.6 dB in the considered band.