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.

This paper addresses the design and development of HiperLAN antennas meeting the IEEE 802.11a standards for wearable applications. Five such antennas are investigated for their performance characteristics, out of which three are conventional copper based antennas and the remaining two are fully fabric antennas. The results reveal that all the proposed antennas are suitable for HiperLAN applications yielding antenna gain in the order of 7-11 dBi. This study demonstrates that fully fabric antennas outperform the copper based antennas.

We investigated a dielectric resonator ceramic microstrip patch antenna. The antenna was formed using barium strontium titanate (BST), which has a dielectric constant of 15. A new approach, i.e., the use of a high temperature dielectric probe kit, was used to determine the dielectric constant of BST. A computer simulation technology (CST) microwave studio was used to simulate the BST array antennas, taking into consideration the dielectric constant. We also measured the gain of the antennas loaded with two-, four-, and six-element arrays of the BST antenna and found that the gain of a six-element BST array antenna was enhanced by a gain of about 1.6 dB over the four-element BST array antenna at 2.3 GHz. The impedance bandwidths of these BST array antennas for voltage standing wave ratio (VSWR) < 2 were in the application ranges, i.e., 2.30 to 2.50 GHz, established for Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN). Compared with the conventional array antenna with the same aperture size, the performance of the antenna obviously was improved, and the design is suitable for array applications, including base stations, for example.

A novel trapezoidal slot patch antenna with an embedded trapezoidal strip is proposed for satisfying wireless local area network (WLAN) and worldwide interpretability for microwave access (WiMAX) applications simultaneously. The proposed antenna consists of a rectangular radiation patch with an etched trapezoidal slot and an embedded trapezoidal strip on the top and a beveled ground on the bottom side. By carefully selecting the width of the radiation patch and length of the beveled ground, the proposed antenna can generate two separate bands. The measured results show that the 10 dB return loss bandwidths of the proposed antenna are 430 MHz (2.30-2.73 GHz) and 3460 MHz (3.21-6.67 GHz), which can cover both the WLAN bands (2.4-2.484 GHz, 5.15-5.35 GHz, and 5.725-5.825 GHz) and the WiMAX bands (2.4-2.6 GHz, 3.4-3.6 GHz, and 5.25-5.85 GHz). Furthermore, good omnidirectional radiation patterns with appreciable gain are obtained over the operating bands.

Cluster-sparse multipath channels, i.e., non-zero taps occurring in clusters, exist frequently in many communication systems, e.g., underwater acoustic (UWA), ultra-wide band (UWB), and multiple-antenna communication systems. Conventional sparse channel estimation methods often ignore the additional structure in the problem formulation. In this paper, we propose an improved compressive channel estimation (CCE) method using block orthogonal matching pursuit algorithm (BOMP) based on the cluster-sparse channel model. Making explicit use of the concept of cluster-sparsity can yield better estimation performance than the conventional sparse channel estimation methods. Compressive sensing utilizes cluster-sparse information to improve the estimation performance by further mitigating the coherence in training signal matrix. Finally, we present the simulation results to confirm the performance of the proposed method based on cluster-sparse.

This paper proposes an algorithm for wide-band microwave imaging for the detection of a hemorrhagic stroke. A realistic head phantom and finite-difference time-domain program are used to estimate back-scattered signals which are subsequently used in the image reconstruction process. The proposed imaging approach can lead to a portable and cost effective system; particularly suitable for rural medical clinics that lack the necessary resources in effective stroke diagnosing.

The monopoles are theoretically defined as charges which produce fields whose divergence is, obviously, different from zero. However, the entities which have been experimentally detected in the spin-ices, with mimetic behavior to that of the magnetic monopoles, generate magnetic fields which seem to be compatible with ∇·B = 0. This apparent contradiction can create confusion and therefore it requires explanation. In this paper we have carried out an analysis of the different electromagnetic fields in the spin-ices materials. We clarify the differences between the average fields of standard Maxwell equations with zero divergence even in spin-ices and the non macroscopic fields when there are magnetic monopoles in these materials. We give the molecular or local fields which allow us to determine the molecular polarizability. We combine the extended Clausius-Mossotti equations with the Lorentz-Drude model for obtaining the extended susceptibility and the optical conductivity which can be used for explaining the action of the electromagnetic fields in spin-ices.

In the present study, we show that it is possible to achieve multi-channel filters in one-dimensional photonic crystals using photonic quantum well structures. The photonic quantum well structure consists of different 1-D photonic structures. We use (AB)₈/C_n/(BA)₈ structure, where A, B and C are different materials. The number of defect layers (C) can be utilized to tune the multi-channel filtering. The filter range can be tuned for desired wavelength with the change in angle of incidence for multi-channel filtering.

In this paper, a novel Metamaterial (MTM) CRLH Zeroth Order Resonance (ZOR) Circular microstrip patch antenna is proposed to have a monopole antenna pattern due to the completely closed loop of a magnetic current around the structure, and reduced profile and size due to the left-handedness. Different from other ZOR antennas of 1D periodic arrays with shorted patches, we suggest 1 circular patch capacitively coupled to 1 circular shorted ring to have ZOR and -1st resonance modes. The antenna is designed and modeled with equivalent circuits for the coaxial-fed central patch and the circular shorted ring and verified by the comparison with 3D EM simulation of the physical structure. The no-phase variation at the ZOR (2.4 GHz) and the -1st resonance mode (2 GHz) as the metamaterial properties are proven with electric field distributions and far-field patterns. The measurement shows there exist the ZOR and the -1 resonance modes despite the frequency shift from the simulation, which is proven by the monopolar radiation pattern and broadside radiation pattern, respectively. So the advantages of the proposed antenna will be addressed with the low-profile monopole at the ZOR and the size reduction effect at the -1st resonance.