This work presents a straightforward way to obtain the coupling matrix of a bandstop filtering response from the original bandpass coupling matrix. The generated bandstop coupling matrix implements a response where the bandwidth is defined at the equiripple return loss of the lower and the upper passbands.

We propose a cylindrical invisibility cloak achieved utilizing two dimensional split-ring resonator structured metamaterials at microwave frequencies. The cloak has spatially uniform parameters in the axial direction, and can work very well even when the cloak shell is very thin compared with the concealed object and the working wavelength. Numerical simulation is performed to verify the functionality of the cloak, where the cloak layer is only around 1/4 of the operating wavelength. Our work provides a feasible solution to the experimental realization of cloaks with ideal parameters.

This paper presents two full differential bandpass filters with small occupied areas. Both filters are designed with the same basic structure which consists of two double coupled resonators with magnetic coupling. The resonators are stacked up and have the advantage of high coupling efficiency, reducing the area. Nevertheless, in the basic structure, the insertion loss in the high stopband is above -10 dB and therefore does not meet the requirement for bandpass filter design. Thus, two solutions are introduced to form the proposed filters. The first one integrates the ground plane, while the second one makes the use of an extra transmission zero. With the help of these solutions, two types of full differential bandpass filters are implemented on an FR4 using the embedded passive device technology, with the additional purpose of being designed for SiP applications. The passband of the filters conforms to the WLAN IEEE 802.11a (5 GHz) standard. Most importantly, the occupied areas of the two proposed bandpass filters are only 6 mm х 6.7 mm and 6.6 mm х 8.3 mm respectively. Compared with previous research, area reductions of up to 98.05% and 97.76% can be achieved.

A technical challenge in hyperthermia therapy is to locally heat the tumor region up to an appropriate temperature to destroy cancerous cells, without damaging the surrounding healthy tissue. Magnetic fluid hyperthermia (MFH) is a novel, minimally invasive therapy aiming at concentrating heat inside cancerous tissues. This therapy is based on the injection of different superparamagnetic nanoparticles inside the tumor. In our study, superparamagnetic nanoparticles, which we developed and characterized, consisted of iron oxide nanoparticles stabilized with polyethylene glycol. Moreover, a new technique for MFH using a specially designed external electromagnetic waveguide as applicator is presented. Three magnetite concentrations were used for making the tumor phantoms, which were embedded in muscle phantoms. The phantoms were radiated and located at three different distances from the applicator. Furthermore, two volumes of tumor (2.5 mL and 5.0 mL) were assayed. Heating curves, as a function of time, allowed the establishment of a more appropriate nanoparticle concentration for obtaining the temperature increase suitable for hyperthermia therapy. The results shown in this paper confirm the feasibility of using nanoparticles as agents to focus the energy over the tumor, without creating hot spots in healthy tissue. In addition, the experiments validated that by using this applicator in combination with nanoparticles, it is also possible to locally control the increments of temperature in tissues.

The literature describing scattering matrices for semi-analytical methods almost exclusively contains inefficient formulations and formulations that deviate from long-standing convention in terms of how the scattering parameters are defined. This paper presents a novel and highly improved formulation of scattering matrices that is consistent with convention, more efficient to implement, and more versatile than what has been otherwise presented in the literature. Semi-analytical methods represent a device as a stack of layers that are uniform in the longitudinal direction. Scattering matrices are calculated for each layer and are combined into a single overall scattering matrix that describes propagation through the entire device. Free space gaps with zero thickness are inserted between the layers and the scattering matrices are made to relate fields which exist outside of the layers, but directly on their boundaries. This framework produces symmetric scattering matrices so only two parameters need to be calculated and stored instead of four. It also enables the scattering matrices to be arbitrarily interchanged and reused to describe longitudinally periodic devices more efficiently. Numerical results are presented that show speed and efficiency can be increased by more than an order of magnitude using the improved formulation.

The main goal of this paper is to present a design procedure for a flexible compact universal UHF RFID tag antenna suitable for worldwide UHF RFID applications. Systematic design procedure is introduced through the derivation of dipole input impedance general relation using induced EMF method considering wire radius effect. T-matched chart is used to match the tag input impedance with the chip input impedance and finally develop a flow chart to summarize the design procedure. The proposed antenna compactness trend is achieved through applying meandering and Franklin shape to conventional printed dipole antenna. Flexibility trend is achieved through using liquid crystal polymer LCP material as antenna substrate. The proposed antenna covers the frequency band 865 MHz to 1078 MHz and occupies an area of 1306.6 mm². The computed radar cross section RCS and conjugate match factor CMF insure that the proposed antenna structure is easily detectable and achieves acceptable matching level. Power reflection coefficient PRC is computed, measured and good agreement is obtained. Other antenna parameters such as radiation efficiency, gain and radiation pattern are also calculated. The proposed antenna is cheap, flexible and suitable for UHF RFID universal application.

The design and simplified analysis of a compact and wide band (16%) negative permittivity complementary split ring resonator metamaterial is introduced. The proposed metamaterial component was applied to reduce the size of the feeding line filter of microstrip patch antenna for the sake of higher order harmonic suppression. The reduction has been done using only one element of the complementary split ring resonator, while maintaining the antenna's performance. Simplified theoretical study and design of the proposed circuits has been presented. Moreover, experimental results have been done for validation and conformation purpose. Results confirm that almost 95% of the antenna noise harmonics power has been removed.

Cylindrical EBG structures excited by a Hertzian dipole source and TM polarized plane wave at oblique incidence are analyzed using a rigorous semi-analytical method based on the cylindrical Floquet mode expansion. Concentric and eccentric cylindrical EBG structures are investigated. Resonance and stopband characteristics in the transmission spectra of the cylindrical EBG structures, enhancement and shading effects in the excited fields, radiation patterns of Hertzian dipole located inside the cylindrical EBG structures in both H-plane and E-plane are numerically studied. Co-polarization and cross-polarizations scattering effects between the electric and magnetic fields are investigated at the oblique incidence of plane waves.

In this paper, a microstrip circuit structure for a K-Band Wilkinson power divider is presented. The designed power divider is composed of two-step taper stubs based on empirical equations. The symmetry of this circuit allows a half circuit analysis through looking at the odd- and even-model excitations. To demonstrate its performance, the proposed Wilkinson power divider has been fabricated and tested. Results show that the measured insertion loss is less than 0.3 dB and that the output reflection, input reflection and isolation are better than 16 dB, 22 dB, 16 dB, respectively, in the frequency range from 18 GHz to 27 GHz.

A key structure in so-called metamaterial mediums is the elementary split-ring resonator. We consider in this paper the low-frequency electromagnetic scattering by a split-ring particle modelled as a perfectly conducting wire ring, furnished with a narrow gap, and derive analytical solutions for the electric and magnetic dipole moments for different kinds of incidence and polarisation in the quasi-static approximation. Through a vectorial homogenisation process, the expressions discovered for the dipole moments and the related polarisability dyadics are linked with the macroscopic constitutive equations for the medium. We further show that the condition for resonance of a medium consisting of simple split-rings cannot be achieved by means of the given quasi-static terms without violating the underlying assumptions of homogenisation. Nevertheless, the results are applicable for sparse medium of rings, and we derive numerical guidelines for the applicability with some examples of the effect of the considered split-ring medium on electromagnetic wave propagation.

In this paper, a novel dual planar electromagnetic bandgap (DP-EBG) microstrip structure is investigated to suppress the spurious radiation of the patch antenna. It is demonstrated that the proposed structure achieves a ultra-wide stopband and excellent passband performance within a compact circuit area. Utilizing such special features, two units of the DP-EBG structure are employed in the feed line of patch antenna with the aim of suppressing harmonics and other spurious modes. The calculated and experimental results all verify that the application of this DP-EBG structure not only drastically diminishes spurious radiations of 2nd ~ 6th harmonics in a broad frequency band, but also overcomes some shortages of other EBG microstrip antennas introduced in previous research such as large back radiation or beam squint. Besides that, by adjusting the separation between the DP-EBG structure constructed in the feed line and the patch's bottom edge in a moderate distance, the procedure for designing the EBG patch antenna working on a certain frequency with the goal of reducing spurious radiation is simplified.

Aluminum conductor steel-reinforced (ACSR) cable is a specific type of stranded cable typically used for electrical power delivery. Steel strands in ACSR cable play a supportive role for overhead power line. Inspection timely is an important means to insure safety operation of power lines. As steel strands are wrapped in the center of ACSR cable, the common artificial inspection methods with optical instruments are limited to find inner flaws of power line. Recently, inspection of power line by robot with detectors is a method with good prospect. In this paper, the optimal design model of detector based on magnetic leakage flux (MLF) carried by robot for detecting broken steel strands in ACSR cables has been proposed. The optimal design model of MFL sensor is solved by niche genetic algorithm (NGA). Field experiment results show that the design method of the detector can be applied to different types of ACSR cables. The magnitude field induced by transmission current has nearly no influences on the detection of broken steel strands, and the developed detector carried by robot can identify broken steel strands with high reliability and sensitivity.

We present a numerical analysis of the interaction between novel scanning near field optical microscopy probes based on an asymmetric structure and a single fluorescent molecule. Our finite element analysis shows how such near field probes can be effectively used for high resolution detection of single molecules, in particular those with a longitudinal dipole moment. At the same time, fluorescent molecules can be exploited as point-like probes of the single vectorial components of the near field distribution at the probe apex, providing a powerful tool for near field probe characterization.

In this paper, a compact wideband high-rejection microstrip bandstop filter using two meandered parallel-coupled lines of different electrical lengths and characteristic impedances in shunt is presented. The transmission and reflection zeros of the filter can be controlled through analytical equations and rulers given. Using this signal interferences technology, this filter obtains a low insertion loss and sharp rejection. Bandwidth and rejection level of the filters of this bandstop filter can be designed by choosing different even- and odd-mode characteristic impedances values of the coupled lines. According to the transmission zeros number, two types of filters are shown in the paper. To validated this topology, a wideband bandstop filter with a 3 dB cutoff frequency bandwidth of 92% centered at 2.6 GHz with sharp rejection characteristics is built to verify the theoretical prediction. The measured frequency response of the filter agrees excellently with the predicted result.

A simple and novel printed monopole antenna with dual broad operating bands is presented. The antenna fed by a 50-Ω microstrip line is composed by dual twin-pair inverted-L shaped strips as well as a small back truncated ground. By properly selecting widths of these inverted-L shaped stripes, dual broad bandwidths formed from triple resonances to meet the band requirement of the 2.4/5.2/5.8 WLAN or the 2.5(3.5)/5.5 GHz WiMAX standard can be achieved. Experimental results for case of the obtained antenna prototype suitable for use in a 2.4/5.2/5.8 GHz WLAN system have been done and shown good agreement with simulation. Good radiation performances including dual wide bandwidths of 270 MHz and 3.16 GHz, high average antenna gains of ≥ 2.6 and 4.6 dBi, and monopole-like radiation patterns over the two operating bands, respectively, make this antenna a good candidate for use in the modern dual-broadband wireless communication system.

In this paper, we present the space-domain integral-equation method for the analysis of frequency selective surfaces (FSS), consisting of an array of periodic metallic patches or a metal screens perforated periodically with arbitrarily shaped apertures. The computation of the spatial domain Green's function is accelerated by the Ewald transformation. The geometric model is simplified by the lattice symmetry, so that the unknowns are greatly reduced. Time of filling MOM matrix and solving linear system is dramatically reduced. Our technique shows much higher efficiency when compared with the available commercial software and the existing methods published.

The existence of reverse radiation noise in the millimeter-wave (MMW) radiometric imaging system with a superheterodyne receiver seriously affects the imaging experiments carried out at short range, thus leading to the degradation of MMW radiometric images and difficulty in recognizing targets. Based on the generation mechanism of reverse radiation noise, the specific influence on imaging for relative radiometry is investigated in this paper, and some methods of eliminating or reducing this noise are proposed. Then, two series of comparative imaging experiments are conducted with a 3 mm band radiometric imaging system. Both theoretical analysis and experimental results are presented to validate the actual existence of interference-like stripes imposed by the reverse radiation noise. Moreover, it is proved that adopting an isolator in the MMW receiving front-end can effectively reduce the reverse radiation noise and significantly improve the imaging performance.

Since its introduction in 1994 direct conversion six-port receivers have attracted a considerable attention at microwave frequencies, with most recent work focusing on the so called six-port receivers with analog $I/Q$ generation. Besides its applications at microwave frequencies, six-port receivers with I/Q regeneration play a crucial role in the optical communications field, as they are the most promising candidates for optical coherent receivers that are being developed for 100 Gigabit Ethernet transceivers. In this paper we analytically model the influence of six-port junction hardware impairments on receiver performance. New analytical expressions are developed which give geometrical interpretation of signal constellation distortion due to hardware impairments and allow for the definition of several interesting figures of merit. Closed formulas are also proposed to analytically calculate BER degradation, under AWGN conditions, from these figures of merit. Finally, the proposed formulas are validated by means of simulation, and it is shown that they can be of practical interest to set the specifications of the six-port junction components.

We have studied a new type of double-negative metamaterials (DNMs) composed of split ring resonators (SRRs) and wire strips with substrate teflon, suitable for generation of reversed Cherenkov radiation (RCR) which is TM radiation. We have experimentally observed a narrow pass band in a circular waveguide partially loaded with the DNMs and stop bands for SRRs-only with teflon and for wire strips-only with teflon, respectively. The experimental data show that the DNMs exhibit double-negative behavior over a frequency band of interest. This study provides a foundation for future experiment to observe RCR emitted by charged particles.

The random wire bundle is an important factor resulting in the randomness of the interferences. This paper studies the effect of random wire positions due to the bundle rotation on the coupling with external fields and presents an efficient method to estimate the averages and standard deviations of the voltages and powers induced on the loads. Three configurations of a four-wire bundle under external fields are investigated by using the Baum-Liu-Tesche equation in the frequency domain and together with the inverse Fourier transform in the time domain, and the results show that the induced voltages and powers change as sine functions when the bundle rotates. The proposed method can estimate the averages and standard deviations of the induced voltages and powers quickly, just by three times repeated analysis, and the results agree well with those obtained statistically.