Wideband Circularly polarized antenna receive much attention in the wireless communication applications such as Global positioning system (GPS) and Personal communication system (PCS). In this paper, a microstrip square patch, truncated in opposite corners, suspended above the ground plane is proposed. The geometry incorporates the capacitive feed strip which is fed by a coaxial probe. The proposed structure is designed, simulated and fabricated to cover the entire frequency of GPS, i.e., L₁ (1.575 GHz), L₂ (1.227 GHz), and L₅ (1.176 GHz), covering from (1.15 GHz-1.6 GHz). The parameters such as return loss, VSWR, impedance, radiation efficiency axial ratio and radiation pattern are used for analyzing the performance of the antenna. Both simulated and experimental results are presented and they exhibit broadband characteristics, covering the desired frequency bands.

A new multilayer power divider with Substrate Integrated Waveguide (SIW) technology is proposed. In this work, two-way and four-way power dividers realizations by two-layer and three-layer SIW, respectively, are presented. Considering the small size of the structure, extension of this method to n-way power dividers and antenna feed networks are possible, and it has the potential for integration of compact multi-layer SIW circuits. Due to the lack of a multiport counterpart of the two-port thru-reflect-line (TRL) calibration, scattering matrix of an n-way power divider must be reconstructed from measured data. A method is introduced for reconstruction of S-parameters of the n-port noncoaxial device with a two-port vector network analyzer (VNA). The two-way power divider is designed for 8.7-10.5 GHz band. Transmission coefficient about -3.5 dB and return loss below -10 dB has been measured for this two-way power divider. For four-way power divider, transmission about -7 dB in the 9.5-10.5 GHz has been achieved.

A dielectric resonator loaded patch antenna excited by a coaxial cable is proposed in this paper. The results from measurement show a wide impedance bandwidth of 57.1% from 3.75 GHz to 6.75 GHz and a peak gain of 11.5 dB at the center of frequency band with an average gain improvement of 3 dB over the frequency band in comparison with the common dielectric resonator antennas. These results are in good agreement with those obtained by the computer simulations. A simple study of the antenna shows that the aperture size increase is the cause of gain enhancement. A theoretical model based on the simulated gain results of reference antenna and its equivalent aperture is presented for the proposed antenna structure with good agreement with simulation and measurement results. The advantages of the proposed antenna are high gain with broad bandwidth, and low fabrication cost in comparison to other types of high gain DRAs having narrow bandwidths and complex structures.

It has been demonstrated in previously published results that large fourth Stokes parameter may be generated from a rough surface over multi-layered media, where only the top interface is rough while the others are all flat boundaries. In this paper, we consider the four Stokes parameters in microwave emission from a two-layer rough surface. In this case, there are two rough boundaries. The rough surfaces vary in one horizontal direction so that the azimuthal asymmetry exists in the 3-D problem. Periodic boundary conditions were assumed. The results are compared with the previously published results from a rough surface over multi-layered media. It is shown that the ``two-layer'' periodic rough surfaces can reduce the vertical and horizontal brightness temperatures remarkably; the interactions between the two rough surfaces also enhance the third and fourth Stokes parameters, which disappear in new structure for the large dips in the vertical and horizontal brightness temperatures presented in the former Sastrugi structure. In particular, the fourth Stokes parameter can be larger than that in previous layered structure. In addition, for the case of sinusoidal rough surface without large slope with snow's permittivities, the top boundary rough only layered structure cannot support the large third and fourth Stokes parameters any longer while the two-layer rough surface structure can do still up to -34 K and 15 K, respectively. It is also found that the reason resulting in the large fourth Stokes parameter is caused by relative magnitude of permittivities of the two layers, all cases with large fourth Stokes parameter should satisfy the upper layer's permittivity larger than the lower one due to total internal reflection from the lower layer.

Uncertainties in an electromagnetic observable, that arise from uncertainties in geometric and electromagnetic parameters of an interaction configuration, are here characterized by combining computable higher-order moments of the observable with higher-order Chebychev inequalities. This allows for the estimation of the range of the observable by rigorous confidence intervals. The estimated range is then combined with the maximum-entropy principle to arrive at an efficient and reliable estimation of the probability density function of the observable. The procedure is demonstrated for the case of the induced voltage of a thin-wire frame that has a random geometry, is connected to a random load, and is illuminated by a random incident field.

ΛOptical bistability (OB) behavior of a Kobrak-Rice 5-level quantum system is investigated. It is demonstrated that the OB of the system can be controlled by either the intensity or relative phase of driving fields. We have also shown that by applying an incoherent pumping field, the OB behavior of the system changes and the considerable output is obtained for zero input in the gain region induced by incoherent pumping field.

Low speed flux-modulated permanent magnet machines (FMPMs) which are based on `magnetic-gearing effect' have attracted increasing attention due to their high torque capability and simple structure. In order to assess the potentials of FMPMs in the application of low-speed direct-drive, two flux-modulated interior PM machines with distributed windings and concentrated windings are quantitatively compared by using finite element method. The results demonstrate that the machine with distributed windings can offer higher peak electromagnetic torques and lower torque ripples. Moreover, the machine with distributed windings also present stronger flux-weakening capability and lower power losses. The results also indicates that the magnetic saturation problem should be paid full attention when design flux-modulated interior PM machine with concentrated windings. If this problem can be well solved, the performance of machine with concentrated windings may be improved.

Two novel compact magic-T configurations designed as a two layer structure are proposed in this paper. They consist of a microstrip tee-junction and resonance circuit composed of a microstrip line combined with rectangular or radial stubs. These microstrip circuits are respectively printed at the top and bottom layers of the structure, and coupled via a slot located in the common ground plane. The microstrip patch and slot are placed parallel to each other forming novel microstrip-slotline transitions, which provide broadband operation of the magic-Ts. Transmission line equivalent circuits are used to explain the performance of the proposed hybrids. It is shown that magic-T with a radial stub demonstrates wider operation bandwidth and better performance than the structure with a rectangular stub. In order to validate their performance, the prototypes of both configurations were manufactured and measured. Experimental and simulation results show that the resulting magic-T using a radial resonator has a fractional bandwidth of over 40% for 0.2\,dB amplitude and 1° phase imbalance. The experimental results are in good agreement well with equivalent circuit and full-wave simulations.

In the paper, the analysis of electromagnetic wave scattering from frequency selective surface is presented. The surface is composed of periodically arranged posts. The multimodal scattering matrix of such structure is derived and the transmission and reflection characteristic for the structure with arbitrary plane wave illumination are calculated. The exact full-wave theory based on the mode-matching method is applied to develop an efficient theory to analyze such structures. The validity and accuracy of the approach are verified by comparing the results with those obtained from alternative methods.

Spatial beam compression of an electromagnetic wave is one of the fundamental techniques employed in microwaves and optics. As there are many ways to achieve this task using the combination of prisms and lenses, recent research suggests the parabolic gradient index photonic crystals (GRIN PC) for the design of spatial beam compressor owing to its functionalities. However, the fabrication of a graded media with the parabolic profile is a difficult challenge in practical realization. To an alternative, present work attempts this problem with respect to the triangular gradient index profile. The performance and aspects of the beam compression are investigated experimentally using the pillar type GRIN PC at the microwave length-scales. The utility of the device for an effective beam injection to the photonic-waveguide component is further demonstrated experimentally.

We calculate the optical force exerted on the nanoparticle close proximity to the surface of fishnet metamaterials based on metal/dielectric/metal films when irradiated at near infrared wavelength. These forces show the resonant frequencies similar to the magnetic resonant frequencies in the double negative index fishnet metamaterial. We also present that the optical force can be enhanced by optimizing the geometry of the fishnet to provide a stronger magnetic resonant dipole. In contrast to the other plasmonic nanostructure always obtaining trapping force using electrical resonant dipole, our presented structure utilizes the magnetic resonance to provide a gradient force, which is suitable for the optical trapping of the nanoscale particles at illumination intensities of just 1 mW/μm², the optical force is sufficient to overcome the Earth's gravitational pull.

This paper presents a practical direction finding receiver based on six-port networks. To expand beam direction angles, improve measurement accuracy, and avoid phase ambiguity, we introduce a dual-baseline architecture into the direction finding receiver. We also propose a calibration technique based on support vector regression (SVR) for the following reasons: The nonlinearity of diode detectors and the asymmetry of six-port junctions can cause measurement phase errors. Moreover, the transmission parameters of two microwave channels differ with changes in received power. Results show that the SVR model can achieve a direction finding accuracy of 0.2932°.

Preparing the 3D-geometry models to perform electromagnetic compatibility (EMC) numerical simulations can be tedious and time consuming. Furthermore, the need to include the test setup in the models, in order to validate the software, by comparing the numerical results with the measured data, may lead to unwieldy simulation models with often unaordable computational costs. In this paper, we provide strategies for optimizing and simplifying the modeling process, together with guidelines for achieving the most unfavorable case in the simulation of EMC problems, as required for a certication process. A test case from the European FP7 HIRF-SE project is analyzed in this paper as an example of how to identify the unnecessary elements for the simulation, while retaining the essential physics of the problem.

A novel compact tree-design antenna (NCTA) with the ability of reconfigurable ultra-wideband (UWB) of 3.1 GHz to 10.6GHz to five multi-narrowband applications is proposed. This antenna has a novel radiating element design that consists of seven small circles (7-filter) surrounding a central circle. Moreover, the NCTA incorporates the 7-filter that functioned as filter into the antenna design. The compact 38mm x 38mm antenna integrates three PIN diode switches, which are connected to a single National Instrument Data Acquisition (NI-DAQ) Board. The DAQ itself is controlled (ON/OFF state) by a virtual instrument known as "Lab VIEW Interface Software". The activation of specific PIN diode switches in the configuration that is controlled by the DAQ then, in turn, determines the frequency agility. The presented antenna is capable of performing up to five multi-bands. The operating frequencies are as follows; band 1 (2.72-11.8 GHz), band 2 (2.4-4 GHz, 5.3-11.6 GHz), band 3 (2.7-6.5 GHz, 7.1-11.6 GHz), band 4 (2.7-4.4 GHz, 5.2-6.5 GHz, 7.1-11.7 GHz) and band 5 (2.6-3.5 GHz, 4.8-7.0 GHz, 7.4 GHz-11.5 GHz). Furthermore, the antenna has a gain of up to 6dBi, which is considered better than that of conventional antenna. The proposed antenna produces a proficient divisive radiation pattern at 4 and 6 GHz. The experimental results exhibit the success of the antenna performance. It is competent as future candidate for cognitive radio and military applications.

Magnetic Induction Tomography (MIT) is a relatively new and emerging type of tomography techniques that is able to map the conductivity distribution of an object. Its non-invasive and contactless features make it an attractive technique for many applications compared to the traditional contact electrode based electrical impedance tomography. Recently, MIT has become a promising monitoring technique in industrial process tomography, and the area of the research interest has moved from 2D to 3D because of the volumetric nature of electromagnetic field. Three dimensional MIT images provide more information on the conductivity distribution, especially in the axial direction. However, it has been reported that the reconstructed 3D images can be distorted when the imaging object is located at a less sensitive region. Although this distortion can be com- pensated by adjusting the regularisation criteria, this is not practical in real life applications as the prior information about the object's location is often unavailable. This paper presents a memory ecient 4D MIT algorithm which can maintain the image quality under the same regularisation circumstances. Instead of solving each set of measurement individually, the 4D algorithm takes advantage of the correlations between the image and its neighboring data frames to reconstruct 4D of conductivity movements. The 4D algorithm improves the image qualities by increasing the temporal resolution. It also overcomes some sensitivity issues of 3D MIT algorithms and can provide a smoother and stabler result. Several experimental results are presented for validating the propose algorithms.

In this paper, two radiation pattern-reconfigurable antennas are designed to operate over DCS 1800 frequency bands. The geometry of the proposed antennas is symmetric with respect to the vertical center line. The electrical shapes of the antennas are composed of a monopole-loaded loop and an open wire. The open wire functions as either a director or reflector for the two antennas. Depending on the switching state, the antennas can select between two beam directions with no input impedance difference. The sizes of each antenna are then optimized to achieve beam switching capability using PIN diodes and FETs. The reflection coefficients and gain patterns for two bias conditions using both switches are measured and compared with the simulated results. The measured results show that the proposed antennas can clearly alternate their beam directions using the switching components.

This research introduces compressed sensing (CS) principle into inverse synthetic aperture radar (ISAR) imaging of non-uniform rotation targets, and high azimuth resolution can be achieved with limited number of pulses. Firstly, the sparsity of the echoed signal of radar targets with non-uniform rotation in certain matching Fourier domain is analyzed. Then the restricted isometry property (RIP) and incoherence of partial matching Fourier matrices are checked, following which an ISAR imaging method based on CS for both random sparse aperture and short aperture cases is proposed. In particular, considering the dependence of the sparse dictionary on the relative rotation parameter, a parameter estimation method by the optimal search in fractional Fourier domain is presented. Simulation experiments verify the effectiveness as well as superiority of the proposed imaging method over traditional methods in terms of imaging performance.

All-dielectric frequency selective surfaces (FSSs) can serve as an alternative to their metallic counterparts when they must operate at very high power, loss must be minimized, or when the surface itself must be low observable. When metals are avoided, there is a weaker interaction with electromagnetic waves and it becomes more difficult to achieve strong suppression in the stop band while also realizing compact size, wide field-of-view or broadband operation. One attractive approach utilizes guided-mode resonance (GMR) as the filtering mechanism, but this phenomenon exhibits several drawbacks that must be overcome for practical application at radio frequencies. This paper introduces the concept of guide-mode resonance for FSSs and describes how they can be made to operate with a dramatically fewer number of periods than conventional GMR devices.

In this paper, we report on the design, fabrication and characterization of a slot antenna on quarter wavelength silicon substrate coupled to a Titanium microbolometer for detection at 94 GHz. The detector was fabricated using conventional photolithographic and microfabrication techniques. The detector exhibited a responsivity of 0.779 V/W, a noise equivalent power (NEP) of 10.2 nW/√Hz, and a time constant of 3.88 μsec.

In this paper, a new design of a dual-polarized antenna with high isolation and low cross polarization is proposed. The main radiation structures comprise two pairs of petaloid patches, which are fed by coaxial lines. Behind the patches, a U-shaped ground is placed to improve the front-to-back ratio of the antenna. Stable and symmetric radiation patterns at slanted ±45° polarization have been obtained within the frequency band 1.71-2.17 GHz. A return loss of -14 dB is achieved and measured isolation between the two input ports is over 31 dB. The 3 dB beamwidths of the two polarizations is stable (65°) and the average gain of the proposed antenna is about 9dBi across the whole frequency band.