This paper presents a novel monopole antenna which uses split ring loading in order to achieve a dual-wideband operation for WLAN (2.4/5.2/5.8 GHz) application. By adjusting the split ring position and its natural resonant frequency, the proposed antenna can produce more than 1 GHz wideband match in the 5 GHz band. According to the measured results, the bandwidth with reflection coefficient less than -10 dB is about 715 and 1017 MHz in the two bands. Good radiation patterns are also achieved. The dimensions of the monopole loaded with split ring are 27.2mm×16.2mm×1mm, which is suitable for a hallway antenna or ceiling mount antenna of WLAN application.

In this paper, a triangular patch antenna (TPA) with 15°-75°-90° angles is studied. The simulation results, using the full wave simulator, IE3D, for this TPA shape are compared with those for the equilateral triangular patch antennas (ETPA), the right angle isosceles triangular patch antenna (RAITPA), the 30°-60°-90° TPA and 30o-30o-120° TPA. It is found that for the same resonant frequency, the 15°-75°-90° TPA occupies the least area among these triangular shapes. In an attempt to verify the simulation results, a 15°-75°-90° TPA operating at 900 MHz is designed, fabricated, and measured. The measured value for the resonance frequency is very close to the value obtained by simulation. Finally, a 15°-75°-90° TPA with a shorting pin is investigated. As expected, a miniaturized patch is obtained by loading a shorting pin at the tip of the patch.

This paper investigate the near-field interaction between the coupling slot and the radiating ones in a dielectric-covered waveguide slot array environment. This interaction can strongly affect the array aperture distribution and input match, mainly when each radiating guide contains few slots or the slot offsets are small. We propose a full-wave Method of Moments approach, taking also into account the waveguide wall thickness, to evaluate this interaction. The use of entire domain basis functions allows to get a small and well-conditioned linear system. The results presented in this paper show that the coupling due to high-order modes in the region of the junction can significantly modify the radiating slot voltage, mainly when the offset is small, and also the array input match, though to a lesser extent.

An Improved Differential Evolution (IDE) algorithm is proposed for optimization problems. With the novel mutant operation adopting sub-optimal individual, the convergence of Differential Evolution (DE) algorithm is accelerated without increasing the risk of premature. Five typical test functions are minimized using DE and IDE algorithms, and the results show the superior performance of IDE algorithm. Furthermore, the algorithm is applied to pattern synthesis of two antenna arrays. Broad nulls are formed in radiation pattern of a linear array to suppress broad-band interferences. In a microstrip patch array, the sidelobe level of array is decreased about 12.9 dB and the mainlobe can scan to the desired angle.

The considerable overlap in the dielectric properties of benign and malignant tissue at microwave frequencies means that breast tumour classification using traditional UWB Radar imaging algorithms could be very problematic. Several studies have examined the possibility of using the Radar Target Signature (RTS) of a tumour to classify the tumour as either benign or malignant, since the RTS has been shown to be influenced by the size, shape and surface texture of tumours. The main weakness of existing studies is that they mainly consider tumours in a 3D dielectrically homogenous or 2D heterogeneous breast model. In this paper, the effects of dielectric heterogeneity on a novel Spiking Neural Network (SNN) classifier are examined in terms of both sensitivity and specificity, using a 3D dielectrically heterogeneous breast model. The performance of the SNN classifier is compared to an existing LDA classifier. The effect of combining conflicting classification readings in a multi-antenna system is also considered. Finally and importantly, misclassified tumours are analysed and suggestions for future work are discussed.

Local multipoint distribution service (LMDS) is a broadband wireless access technology that operates at microwave frequencies above 25 GHz. However, severe attenuation due to excessive rain in tropical regions presents a major challenge for achieving reliable communication over such frequencies. To overcome this problem, cell-site diversity (CSD) can be deployed in cellular-type LMDS networks. In this paper, we address the problem of reliable communication for LMDS networks in heavy rain regions by proposing a fuzzy weight controller based cell-site diversity (FWC-CSD) scheme. Rain cells are randomly simulated in an LMDS network to analyze the system performance using the proposed FWC-CSD scheme. Simulation results show that the proposed scheme yields improved performance in terms of average outage probability and throughput while maintaining the overall quality of service.

The early identification of malignant tissue is one of the most significant factors in the successful treatment of breast cancer. Microwave imaging is an emerging breast screening modality based on the dielectric contrast between normal and cancerous tissues at microwave frequencies. When the breast is illuminated with an Ultrawideband (UWB) microwave pulse, the dielectric contrast between normal and cancerous tissues generates electromagnetic reflections. These reflected signals, containing tumor backscatter, are spatially focused using a beamformer which can compensate for attenuation and phase effects as the signal propagates through the breast. However, recent studies have shown the breast to be a dielectrically heterogeneous entity. High levels of heterogeneity reduce the dielectric contrast between normal and cancerous tissue, limiting the effectiveness of beamforming algorithms. One possible method to assist in the diagnoses of cancer in a heterogeneously dense breast is the use of contrast agents. Contrast agents modify the dielectric properties of a malignant tumor site in order to increase the dielectric contrast with fibroglandular tissue. In this paper, a number of beamforming algorithms are applied to MRI-derived models with endogenous and contrast enhanced malignant tissue properties. Two contrast agents are applied to heterogeneously dense breast phantoms and simulations are carried out prior and post contrast agent delivery. A range of tumor diameters are simulated and a number of beamforming algorithms are applied to the simulated data. The resulting differential scans are then compared across a range of appropriate metrics.

A full-wave approach is proposed to evaluate the shielding performance of metallic rectangular double-stage cascaded enclosures with apertures. The analysis has been carried out by means of the mode-matching technique and the mixed potential integral equation solved with the Method of Moments. The effects of the dimension of enclosures, the orientation of apertures, the polarization direction of the incident wave, the aperture thickness and the high-order modes propagating in enclosures are taken into account. The accuracy of the proposed approach is validated by comparing with other methods and numerical simulation results can derive some conclusions: the shielding performance of cascaded enclosures is better than that of single-stage enclosures, the shielding effectiveness can be improved with increasing the distance between stages in the range, and the shielding performance of the double-stage enclosure with parallel-pattern apertures in horizontal polarization case is better than that in vertical polarization case.

The scattering analysis from metallic Grid FSS consisting of rectangular perforations on a thick metallic screen illuminated by an oblique incident plane wave is presented. The grid structure is analyzed using Scale Changing Technique (SCT) which is based on the partition of the grid-plane into planar sub-domains defined at various scalelevels. Electromagnetic interaction between subsequent scales is modeled by mutually independent Scale-Changing Networks and finally the complete structure is simply represented by a cascade of these networks. Very good agreement is obtained between simulation results from SCT and the Finite Element Method (FEM) when computing the reflection/transmission coefficients and electromagnetic field backscattered by thick and finite size frequency selective surfaces. The computation time is significantly reduced when using SCT-based software compared with the FEM simulation tool.

A 3-bit phase array system including phase shifter blocks and antenna elements has been developed on a coplanar waveguide (CPW) using micro electromechanical system (MEMS) technology. The non Euclidean Koch fractal geometry has been used to improve the frequency behavior of the entire system. It is shown that the fractal geometry makes the design to have lower profile, wider frequency bandwidth, and lower mutual coupling effects. It also decreases the actuation voltage of the MEMS switch elements. The fabrication process has been fully described and the measured values regarding every single block is presented.

In implementing electromagnetic vulnerability (EMV) testing on operational helicopters fielding a variety of avionic, communication, and weapons systems, the testing levels as spelled out in MIL-STD-464A require most test labs to position the high power source antennas unreasonably close to the test item (sometimes within 2 m). Questions naturally arise concerning the efficacy of such testing with respect to both the manner of coupling of the fields to the helicopter systems as well as the levels required to achieve reasonable confidence in the coupling effects. This paper presents a comparison of the electric fields interior to an axially slotted circular cylinder and the fields in the slot aperture as a function of the distance from the source to the test item. Also, these measured interior and aperture fields are compared to two different mathematical/numerical models of the conducting cylinder with an axial slot running the length of the cylinder. Additional measurements are presented for the fields interior to a finite cylinder with conducting endcaps and a significantly reduced slot of finite length. Comparisons to one of the mathematical/numerical models for this finite length cylinder with finite length slot are presented also.

An efficient double superimposition model (DSM) is proposed to generate two-dimensional (2-D) ocean surface waves. On the basis of this efficient model, a modulated slope-deterministic facet model (MSDFM) is developed to compute the radar cross section (RCS) of synthetic aperture radar (SAR) for the generated ocean surface. Then, the properties of the SAR imaging mechanism for wind seas are discussed from a combination of SAR and ocean wave parameters. Furthermore, a hybrid facet scheme, which is the combination of physical theory of diffraction equivalent edge currents (PTDEEC) and physical optics (PO) method, is introduced to analyze the high frequency scattering characteristics of large ship target. Finally, this hybrid facet scheme combines with the four-path model and MSDFM to investigate SAR imaging for the composite model of ship on dynamic ocean scene. The resolution degradation of ship-ocean model arising from different facet velocities within a SAR resolution cell and the range migration caused by coupling scattering are investigated in this paper. SAR imagery simulations of marine scene are illustrated, proving the validity and practicability of the presented algorithms.

In this paper a square monopole antenna has been proposed which can be used for Ultra Wideband applications. Band-notch performance is introduced by an E-shaped slot on the patch. The dimensions are optimized to give not only the usual 3-10 GHz bandwidth with rejection in the 5-6 GHz band which is commonly used for WLAN, but also short received pulse duration when transmitted and received using a pair of these antennas. The demonstration of short received pulse-width is the primary novelty reported. The performance is verified by time domain measurements, in addition to the usual antenna characterization.

Research on digital modeling and realization of non-correlation measurement frame for compressive sensing (CS) is conducted aiming at applying CS to imaging radar. FPGA based Analogue-to-Information Converter (AIC) is proposed and implemented. Real measurement data from AIC hardware platform and simulation data from AIC software platform are compressed to get range profiles, and the results agree well with what expected. The results show that the noise and synchronization error in real system deteriorate the performance of AIC thus CS remarkably.

A new design of microwave band pass filter design is presented using metamaterial-inspired Epsilon Near Zero (ENZ) and Mu Near Zero (MNZ) behaviors. These filters are based on waveguide technology. The proposed structure allows us to reduce the number of tunnels normally used for passband filter design by reducing its size. It is also incorporated the half mode concept to the tunnels leading a greater miniaturization. Two Chebyshev filters with two and four-poles were designed, fabricated and measured showing good agreement between simulated and experimental results.

We investigate the localized surface plasmon resonances (LSPR) of a pair of dielectric-core/silver-shell nanospheres, with and without a silver nanobar connecting them, for different values of the permittivity of the dielectric core, using the finite element method. Results show that the structure of a pair of core shells with a nanobar possesses a distinct blue-shifted behavior that can be manipulated from near infrared to visible light. The near field intensity can be enhanced by several orders of magnitude and the working wavelengths depend on the shell thickness, dielectric medium in hollow metallic shell and the diameter of the nanobar. In addition, three or more pairs of nanospherical chain waveguides have also been investigated in our simulations.

To meet the requirements for broadband operation, high port-to-port isolation, and miniature chip area, a doubly balanced monolithic microwave ring mixer with an advanced IF extraction fabricated using 0.15 μm GaAs pHEMT process is presented. A miniature Marchand-like spiral balun with low-pass filter is used to extract IF signals and maintain balun performance simultaneously. The low-pass filter can filter out both the RF and LO signals. This miniaturized mixer design can mitigate layout complexity, improve port-to-port isolations suitable for ultra-broadband Ku-, K-, and Ka-band applications. Subsequently, the LO/RF-to-IF isolations are greater than 43.2 and 32 dB from 11 to 40 GHz, respectively. The LO-to-RF isolation is between 26.9 and 50.7 dB within the same swept range. The conversion loss is 7.2-12.4 dB within the operating bandwidth.

A planar array composed of 41 parasitic dipoles, above a ground plane, fed by an active dipole at 5 GHz, was designed to obtain a pencil beam pattern with a moderate gain and bandwidth. Experimental results are in good agreement with the theory and show a pattern with an 18.78 dB gain, a sidelobe level (SLL) of -15 dB, an impedance bandwidth of 16.53% (the frequency range over which the value of S11 is below -10 dB) and a 2.7% bandwidth that is achieved within 1 dB gain variations.

This paper presents a novel permanent-magnet (PM) machine for wind power generation. In order to achieve high power/torque density as well as get rid of the nuisances aroused by the mechanical gearbox, a coaxial magnetic gear (CMG) is engaged. Different from the existing integrated machine in which armature windings are deployed in the inner bore of the CMG as an individual part, stator windings are directly inserted among the slots between the ferromagnetic segments in this proposed machine. Thus, it can offer several merits, such as simpler mechanical structure, better utilization of PM materials and lower manufacturing cost. Moreover, by artfully designing the connection of the armature windings, the electromagnetic coupling between the windings and the outer rotor PMs can be dramatically decreased, and the electromechanical energy conversion can be achieved by the field interaction between the inner rotor PMs and the armature windings. This machine adopts an outer-rotor topology, for compact design, the wind blades are directly mounted on the outer rotor of the machine, while the fairing is equipped on the front end of the stator. The design details and operating principle are elaborated. By using the time-stepping finite element method (TSFEM), the electromagnetic characteristics of the proposed machine are analyzed. The results verify the validity of the proposed machine.

A novel kind of room temperature terahertz photodetector based on Electromagnetically Induced Transparency (EIT) is presented. The main idea for room temperature and THz range operation is reduction of dark current which is done by converting of the incoming terahertz signal (long-wavelength Infrared signal) to short-wavelength field through EIT phenomena. For realization of this idea, we examine EIT phenomena in multi levels atomic system and quantum wells cascade structures. In the proposed structure the quantum interference between long wavelength and short-wavelength radiation modifies the absorption characteristic of short-wavelength probe field. By this means, the terahertz signal does not interact directly with ground state electrons, but affects on the absorption characteristics of the short-wavelength or visible probe optical field which directly interact with ground state electrons. Therefore, the important thermionic dark current in terahertz detection, can be strongly reduced. So, the proposed idea is appropriate for terahertz and room temperature applications.