In this paper, properties of three types of Circular Polarization Selective Surface (CPSS) cells including Pierrot, Morin, and Tilston, for using in dual circular polarization reflectarray antenna design are investigated. First they are designed for a center frequency about 10 GHz, and circular polarization properties including Reflection Loss, Transmission Loss, Reflected Axial Ratio, and Transmitted Axial Ratio are calculated and presented. Finally, reflection phase curves are presented, and the comparison between simulated properties is accomplished. Simulations show that Tilston cell is more optimum in dual circular polarization reflectarray antennasr

A compact balanced UWB bandpass filter (BPF) is proposed in this paper, which is based on the half-mode substrate integrated waveguide (HMSIW) and the differential defected ground structure (D-DGS). Using the HMSIW, the filter can achieve compact size, wide passband and good compatibility. Two D-DGS cells are employed to provide good suppression for the common-mode (CM) noise, while they have small effect on the performance of differential-mode (DM) signals. To validate the design theory, a microstrip balanced UWB BPF is designed, fabricated and measured to meet compact size, low insertion loss, good return loss as well as proper bandwidth. The predicted results are compared with measured data and show reasonable agreement.

An analytical expression of an Airy-Gauss beam passing through a fractional Fourier transform (FRFT) system is derived. The normalized intensity distribution, phase distribution, centre of gravity, effective beam size, linear momentum, and kurtosis parameter of the Airy-Gauss beam are demonstrated in FRFT plane, respectively. The influence of the fractional order p on the normalized intensity distribution, phase distribution, centre of gravity, effective beam size, linear momentum, and kurtosis parameter of the Airy-Gauss beam are examined in FRFT plane. The fractional order p controls the normalized intensity distribution, phase distribution, centre of gravity, effective beam size, linear momentum, and kurtosis parameter. The period of the normalized intensity, phase, and centre of gravity versus the fractional order p is 4. The period of effective beam size, linear momentum, and kurtosis parameter versus the fractional order p is 2. The periodic behaviors of the normalized intensity distribution, phase distribution, centre of gravity, effective beam size, linear momentum, and kurtosis parameter can bring novel applications such as optical switch, optical micromanipulation, and optical image processing.

In this paper, we propose novel omnidirectional UWB printed monopole antenna for in-body microwave imaging applications. The proposed antenna consists of a square radiating patch, a microstrip feed line and a ground plane with pair of rotated T-shaped slots and another T-shaped slot that placed in between of two slots. The designed antenna provides a wide usable fractional bandwidth of more than 136.5% (2.96-15.8 GHz). This antenna has the advantages of wide bandwidth, compact size, low cost, good omnidirectional radiation patterns, and acceptable time domain behavior for using in In-Body microwave applications. The maximum measured gain for the fabricated antenna is around 6.1 dBi with an average efficiency above 89% throughout the bandwidth.

A center-feed dual-band dual-polarized circular microstrip antenna employing the curved slots on the ground is proposed. The proposed antenna radiates φ-polarization by introducing 10 units of curved slots symmetrically on the ground and θ-polarization by the coaxial probe at the center. The measured results show that the proposed antenna provides two resonant bands, TM₀₁ and TM₀₂ modes, covering the frequency bands of the WLAN (2.4-2.484 GHz) with an omnidirectional right-handed circular polarized (RHCP) radiation pattern and the WiMAX (3.3-3.6 GHz) with an omnidirectional horizontal polarized radiation pattern, respectively. In addition, the effects of the unit number of the curved slots and the width of the slots on the frequency ratio of these two resonant frequencies are studied. Furthermore, for the low profile of 0.056 λ₀ and good omnidirectional characteristic, the antenna is suitable for the modern multi-band wireless communication systems.

The focusing properties of radially polarized hypergeometric Gaussian beam are studied using the Richards-Wolf vectorial diffraction model. Such a polarized beam is decomposed into radial and longitudinal polarization. With a proper combination of the beam order, beam size and imaginary parameter variables, the adjustably confined flat-topped focus and focal hole can be obtained in the focal region. Moreover, we got originality characteristic for the axial intensity distribution of two shaped symmetric light spots. The tight focusing of a hypergeometric Gaussian beam may find applications in data storage, laser drilling, optical trapping, etc.

Variety of designs for artificial magnetic materials have been proposed in the literature. in most designs such as split-ring resonators, the inductive and capacitive responses of metallic inclusions are dependent since the area and perimeter of the resonators' geometry cannot be tuned independently. In this work, three generic resonators for the design of artificial magnetic materials are proposed. The resonators are called rose curve resonator, corrugated rectangular resonator, and sine oval resonator. The proposed resonators' patterns are characterized so that their areas and perimeters vary independently. Thus, the geometries are capable of satisfying any realizable combination of area and perimeter designed for an artificial magnetic material with desired properties. Numerical studies are considered showing the effectiveness of the new geometries to fulfil design specifications.

A number of transverse stratified configurations of metal and dielectric layers are studied for modulating Terahertz radiation in amplitude and phase. Pass band flat-top response and high wide-band transmission is achieved by means of a metallic grating filled with Liquid Crystal (LC) in different configurations and with the use of either grazing angles of incidence or cuts pierced within the grating. The transverse configuration with thin LC films allows for high speed tunability with low applied voltage. A dielectric grating with non-continuous electrodes is studied showing wide pass band response suitable for phase modulation applications.

This study concerns the 2D inverse problem of the retrieval, using external field data, of either one of the two physical parameters, constituted by the real and imaginary parts of the permittivity, of a z-independent cylindrical dielectric specimen subjected to an external, z-independent, quasistatic electric field. Six other parameters enter into the inverse problem. They are termed nuisance parameters because: 1) they are not retrieved during the inversion and 2) uncertainty as to their actual values can adversely affect the accuracy of the retrieval of the permittivity. This inverse problem is shown to have an exact, mathematically-explicit, solution, both for continuous and discrete input data, whose properties, with respect to the various nuisance parameter uncertainties, are analyzed, first in a mathematical, and subsequently in a numerical manner for noiseless data. It is found that: a) optimal inversion requires data registered at only a small number of sensors, b) the inverse solution, satisfying pre-existing physical constraints, exists and is unique. Moreover, the inverse solution is shown to be unstable with respect to three nuisance parameter uncertainties, the consequence of which is large retrieval inaccuracy for small nuisance parameter uncertainties, acting either individually or in combination.

A dual-polarized multiple-input-multiple-output (MIMO) antenna integrated with electromagnetic band-gap (EBG) is proposed. The MIMO antenna consists of two dual-polarized (0°and 90° polarizations) antenna elements. Each element includes four symmetrical arc-shaped slots. A mushroom-shaped EBG structure with four slots at its fringe is designed to enhance the gain of MIMO antenna. The bandwidth (return loss > 10 dB) of the proposed antenna is from 5.70 to 5.93 GHz, and the peak gain is 5.45 dBi. The isolation between the ports of adjacent antenna elements can be as small as less than -20 dB. The dual-polarized MIMO antenna with EBG has a compact volume of 44.5×77.5×1.6 mm³ and canbe suitable for 5.8 GHz WLAN application.

A novel dual-helix monopole antenna with circular polarization (CP) operation is proposed. By utilizing a pair of asymmetrical strip-sleeves shorted at the ground plane, the proposed CP design at 2.45 GHz ISM band can easily be achieved and provides the impedance bandwidth (RL≧10 dB) about 240 MHz and the 6 dB axial-ratio (AR) bandwidth about 126 MHz. The measured peak gain and radiation efficiency are about 9.1 dBic and 81% across the operating bands, respectively.

This paper presents a compact multilayer hybrid coupler based on a microstrip viatransition and short transmission line with a capacitor on each side to reduce circuit size. The microstrip via-transition is connected to two microstrip lines in different layers to configure a sandwich structure. To reduce the passive component circuit size, the design method uses a microstrip via-transition and a short transmission line with capacitors on each side. To validate the microstrip via- transition and short transmission line with capacitor, a multilayer hybrid coupler is implemented at a center frequency of 2 GHz. The measured characteristics agreed well with the simulation results, and above 90% circuit-size reduction compared with conventional couplers was realized.

A low-power on-off-keying impulse-radio (IR) ultra-wideband (UWB) pulse generator (PG) intended for wireless-powered IR-UWB radio applications is presented. The proposed PG has high flexibility, the center frequency, output power and pulse-width (PW) are controllable depending on channel conditions and data rates. Qualitative frequency-domain and transient analyses are presented. A new figure-of-merit (FoM) is proposed such that a more precise comparison between different PGs can be made. The PG is successfully implemented in a TSMC 90 nm CMOS process, measurements show the energy consumption and FoM to be 2.8-7.5 pJ/pulse and 1.6-2.6% respectively. The output swing and PW are 277-329 mV_p-p and 509-1088 ps respectively. The core area is 0.092 mm².

Magnetic lens based on metamaterials has helped to increase the inductive coupling of two-coil system in wireless power transfer. By coordinate transformation, the spatially mapped metamaterials are proposed in this paper for a new magnetic concentrator in two-coil system to improve the mutual coupling. To achieve such metamaterials, the virtual rectangular domain is spatially mapped into a deformed spherical shell. The effects of such mapped spherical shell, functioning as magnetic concentrator, are simulated and evaluated. The fabrication and simplification of this magnetic concentrator are also considered. Finally, this model of spherical shell is compared with that of a traditional magnetic concentrator to demonstrate its advantage.

A time-efficient method is proposed to calculate the near-field time-domain physical-optics (TD-PO) integral to analyze the transient electromagnetic fields scattered from three-dimensional perfectly conducting objects under the illumination of a pulsed plane wave. It is shown that the TDPO integral can be reduced to a close-form expression by introducing locally expanded Green-function approximations used in conjunction with the surface partitioning. As a result, the near-field TD-PO response to a general pulsed plane wave excitation is derived by a convolution of the excitation waveform with the TD-PO impulse response, which can be performed in a closed form. To satisfy the causality, i.e., the transient field cannot travel away from the sources faster than the speed of light, the high-order derivative of a modulated-Gaussian wave is specified as the excitation waveform. The efficiency and accuracy of the proposed near-field formulas are validated through numerical examples.

In this article, a novel compact triple-band monopole antenna for WLAN/WiMAX applications is proposed. The proposed antenna is designed on an FR-4 substrate with thickness of 0.8 mm, relative permittivity of 4.4, and loss tangent of 0.02. It consists of a square ring, an open ended stub, and an inverted T-shaped stub. Three bands covering 2.3-2.76, 3.387-3.73, and 4.97-6.28 GHz are achieved, which cover all the 2.5/3.5/5.5 GHz WiMAX and 2.4/5.2/5.8 GHz WLAN operation bands. Moreover, the presented antenna has a compact size of 24 × 36 mm². Experimental results show that the proposed antenna gives good gains and has nearly omnidirectional radiation patterns across all the operation bands.

A new method for designing compact Wilkinson power dividers with three order harmonics suppression is presented. The quarter-wavelength transmission line in the traditional Wilkinson power divider is replaced by two pairs of parallel coupled lines with one end connected in series with an open stub. With this structure, the quarter-wavelength line will be shorter and three attenuation poles can be added in the stopband. As a result, this newly proposed structure carries the functions of impedance matching at operating frequency and three orders harmonics suppression. In this study, an example of power divider operating at 1 GHz is designed and fabricated. The measured results show good performance at the operating frequency. In addition, the second, third and fourth harmonics suppressions are 43 dB, 49 dB and 37 dB, respectively, which validates the feasibility of the proposed design.

In high power operations, the ageing of power semiconductor modules has been often observed by several failures due to high temperature cycling. The main failures may be metallization reconstruction, solder delaminations, bond wire lift-offs or bond wire heel crackings, conchoidal breaking of ceramics. The paper focuses on the non-contact monitoring of the ageing of the aluminum metallization top layer and of the solder bottom layer of a power die, using the eddy current method. The ageing is assumed to induce a decrease of these layers conductivity. The evaluation of both layers conductivity changes are estimated using artificial neural networks starting from eddy current data provided by finite element computations carried out in the case of several aged die configurations. The error of estimation is less than a few percent in the considered cases and it demonstrates the relevance of the eddy current method to monitor the ageing state of power modules. The proposed approach provides relevant results which will be validated on experimental data in future works.

A waveguide standard is introduced for validation purposes on the measurement accuracy of electric and magnetic properties of materials at microwave frequencies. The standard acts as a surrogate material with both electric and magnetic properties and is useful for verifying systems designed to characterize engineered materials using the Nicolson-Ross-Weir technique. A genetic algorithm is used to optimize the all-metallic structure to produce a surrogate with both relative permittivity and permeability within a target range across S-band. A mode-matching approach allows the user to predict the material properties with high accuracy, and thus compensate for differences in geometry due to loose fabrication tolerances or limited availability of component parts. The mode-matching method also allows the user to design standards that may be used within other measurement bands. An example standard is characterized experimentally, the errors due to uncertainties in measured dimensions and to experimental repeatability are explored, and the usefulness of the standard as a verification tool is validated.

Decomposition of the electromagnetic energy into its stored and radiated parts is instrumental in the evaluation of antenna Q and the corresponding fundamental limitations on antennas. This decomposition is not unique and there are several proposals in the literature. Here, it is shown that stored energy defined from the difference between the energy density and the far field energy equals the energy expressions proposed by Vandenbosch for many but not all cases. This also explains the observed cases with negative stored energy and suggests a possible remedy to them. The results are compared with the classical explicit expressions for spherical regions where the results only differ by the electrical size ka that is interpreted as the far-field energy in the interior of the sphere. Q