This research work proposes an efficient four-wave mixing (FWM) based routing and wavelength assignment (RWA) scheme for the improvement of connection blocking probability in WDM/DWDM networks. However, the traditional RWA schemes are less efficient for the better quality of transmission, and the proposed RWA scheme partitions the entire fiber transmission window into N number of bands and assigns wavelength randomly from one of the band based on connection length. Finally, the analytical result proves that the mechanism reduces the FWM effect significantly in terms of connection blocking probability with higher partition, lower FWM effect and better performance.

This paper deals with an efficient methodology aimed at monitoring the radiated electromagnetic emissions along a high-speed railway system in the hundreds of kilohertz range. In particular, the proposed approach allows a compressed representation of the spatial distribution of the frequency spectrum of the radiated magnetic field generated by the currents placed on the railway conductors by electrical apparatus on board of running railway vehicles. The main idea underlying this work is that the standing wave nature of current distribution along the railway line results in a spatial distribution of radiated magnetic field which can be effectively represented by resorting to the emerging compressive sensing theory. To this aim, wireless magnetic-field sensors are assumed to be deployed along the railway line and used to provide spatial samples of the magnetic field spectrum. The main advantages of the proposed approach include a smaller number of sensors when compared with the number foreseen by the straightforward use of the conventional Nyquist-Shannon sampling approach, and a simple treatment of nonuniform spatial distribution of sensors. Suitability of the proposed approach is supported by measurement data and electromagnetic models already available in the related literature, whereas effectiveness of field spatial reconstruction is proved through numerical simulations. Although the application presented in this work is specific to the magnetic field distribution in a limited frequency range, the proposed approach has a general validity and could be effectively exploited for distributed monitoring of other physical quantities, in other frequency ranges, related to electromagnetic compatibility and safety/security issues in high-speed railway systems.

A novel wide band microstrip line-fed antenna with defected ground structure is proposed for circularly polarized characteristics. This antenna is suitable for C-band and partially X-band operation. Antenna1 structure consists of microstrip-line-feed, and the square-shaped slot with defect is incorporated in the ground plane. Furthermore, a rectangular and circular patch embedded in the square slot that improves the performance of the radiating Antenna2 and Antenna3 structure, respectively. The proposed Antenna3 is compact in size and shows a good quality of polarization at resonant frequency band. Antenna3 shows the measured impedance bandwidth of 40.72 % (6.45-9.75 GHz) and also shows the variations of 3-dB axial ratio bandwidth at the 6.806 GHz and 9.13 GHz frequencies with the simulated results, respectively. The return loss, axial ratio, gain, efficiency and radiation pattern of the proposed Antenna3 remain consistent for resonant frequency band. The antenna is practically fabricated and simulated. Measured result shows a good agreement with simulated and theoretical ones.

This paper introduces novel derived transformation equations to design Tri-band filters. The design utilizes the approach adopted for tri-band bandpass filter design based on asymmetric half-wavelength resonator. The obtained optimized filter by this approach is used as a reference, and the proposed transformation is applied to calculate the new filter design hardware parameters that satisfy its given specifications. The reference tri-band filter is designed to have: insertion better than 1.3 dB and return loss less than -10 dB at the resonance frequencies 1.4 GHz, 4 GHz and 5.6 GHz for L-Band DAB, Radar (G-band) and Radar (C-band) applications, respectively. To verify the transformation technique two tri-band filters are designed. The first tri-band filter is for WVL, WiMAX and WiLAN while the second tri-band filter is for UMTS, WiLAN and X-band Satellite applications. The momentum simulations for these filters show that the resulting filters specifications are: the insertion loss is better than 1.3 dB and the return loss is less than -10 dB at the resonance frequencies 1.3 GHz, 3.6 and 5.7 GHz for the first one. While the insertion loss is better than 1.4 dB and the return loss is less than -10 dB at the resonance frequencies 1.9 GHz, 5.35 GHz and 8.25 GHz for the second filter, respectively. A set of prototype of the final design of the proposed filters with optimal parameters was fabricated for experimental verification. The RT 5880 substrate is utilized in this design All the results are obtained using circuit and momentum simulation of the Agilent Design Simulator (ADS) package and the performance characteristics have been measured using the Rohde & Schwarz ZVB20 vector 4 port network analyzer. Analysis and comparison of the obtained results show that all the simulated and the measured results agree well.

In this paper, a dual-band circularly polarized (CP) patch antenna with left-hand circular polarization (LHCP) in the lower band and right-hand circular polarization (RHCP) in the higher band is proposed. On the basis of aperture coupled feed, the dual-band circular polarizations are achieved by adopting two rectangular patches with different rotation angles on the front and back of a substrate. A good agreement between the simulated and measured results is obtained. The 10-dB impedance bandwidths and 3 dB Axial Ratio (AR) bandwidths are 18.4% (1.93-2.32 GHz) and 3.2% (2.14-2.21 GHz) in the lower band and 12.4% (2.58-2.92 GHz) and 1.7% (2.84-2.89 GHz) in the higher band, respectively. The proposed antenna with its simple structure, compact size and excellent performanceprovides a reference forcommunication system applications.

This paper presents a method for improving Angle-of-Arrival estimation accuracy in multipath environments using a sliding antenna array consisting of only two antennas. The proposed method is then experimentally validated by means of a dual channel Software-Defined Radio receiver and a wireless microphone.

We present an extremely sub-wavelength negative index metamaterial structure operating at radio frequency. The unit cell of the metamaterial consists of planar spiral and meandering wire structures separated by dielectric substrate. The ratio of the free space wavelength to unit cell size in the propagation direction is record breaking 1733 around the resonance frequency. The proposed metamaterial also possesses the most extreme refractive index of -109 that has been recorded to date. Underlying magnetic and electric response originate from the spiral and meandering wire, respectively. We show that the meandering wire is the key element to improve the transparency of the negative index metamaterial.

A scheme for efficiently solving the nonlinear electromagnetic inverse scattering problem on sparse investigation domains is described. The proposed scheme reconstructs the (complex) dielectric permittivity of an investigation domain from fields measured away from the domain itself. Least-squares data misfit between the computed scattered fields, which are expressed as a nonlinear function of the permittivity, and the measured fields is constrained by the L₀/L₁-norm of the solution. The resulting minimization problem is solved using nonlinear Landweber iterations, where at each iteration a thresholding function is applied to enforce the sparseness-promoting L₀/L₁-norm constraint. The thresholded nonlinear Landweber iterations are applied to several two-dimensional problems, where the ``measured'' fields are synthetically generated or obtained from actual experiments. These numerical experiments demonstrate the accuracy, efficiency, and applicability of the proposed scheme in reconstructing sparse profiles with high permittivity values.

This paper proposes a double negative metamaterial surface as a superstrate for a multilayer cylindrical dielectric resonator antenna (MCDRA). The aim is to achieve a broadband and high gain Electromagnetic Band Gap (EBG) antenna that can be used in harsh propagation areas to satisfy all the requirements for the 60 GHz wireless communications offering a bandwidth of 7 GHz in the unlicensed ISM band (57−65 GHz), permitting to reach data rates of 10 Gbit/s and more. To meet these objectives various techniques are combined. Numerical and experimental results showed satisfactory performances with achievable impedance bandwidth of more than 10.5% (from 58.1 to 64.2 GHz) and a 18 dBi gain, an enhancement of 13 dBi compared to a homogenous DRA without metamaterial superstrate. The proposed antenna exhibits directive and stable radiation pattern in the entire operating band.

Extracting instantaneous frequency (IF) of Micro-Doppler (M-D) is the key to estimating Micro-motion parameters. In this paper, firstly, the micro-motion model of the coning was set up. Meanwhile, the theoretical analysis and derivation of the micro-Doppler were performed. Then we introduced occlusion effect and Time Frequency transform to better accord with the complexity and reality of feature extraction of Micro-Doppler in the real world. Besides other computational complex separation methods, we extended the Viterbi algorithm for some cases and proposed two novel means, selecting local maximum value and extracting central position, to solve the dilemma which unable the Viterbi algorithm. Finally corresponding simulation correct the performance of the two methods in different Signal to Noise Ratio (SNR).The simulation analysis showed that the methods were effective if time-frequency map was not polluted seriously by noise.

Perfectly Matched Layer (PML) is modeled by Split-Field FDTD (SF-FDTD) in order to simulate Radar Cross Section (RCS) of a plasma slab. PML is used as an absorbing boundary, and discrete plane wave (DPW) is employed to generate plane wave. DPW method has a power isolation of -300 dB between scattered-field and total-field regions. The dispersive media is modelled by shift-operator FDTD. In this article, the SO-FDTD and DPW are combined, and it is proved that this combination shows a good stability. Finally, two different plasma profiles (exponential and polynomial) are used to prove reflection coefficient of a conductive layer can be reduced by choosing true profile of covering layer. By using Near-to-Far-Field Transformation, all fields are transferred to far-field region to calculate RCS.

In this paper, a novel wideband single-feed circularly polarized patch antenna is presented. The antenna consists of an L-shaped probe, four parasitic patches perpendicular to the probe, and a planar reflector. By modifying the structure of the patches, two orthogonal radiation modes are created to realize the circular polarization in the broadside direction. This antenna exhibits a wide impedance bandwidth of 82.4% from 2 GHz to 4.8 GHz for the voltage standing wave ratio (VSWR) ≤ 2 and a 3-dB axial ratio (AR) bandwidth of 56.2% from 2.11 GHz to 3.77 GHz, over which the antenna gains vary from 5.7 dBic to 9.7 dBic. The measured results agree well with the simulated ones.

Covariance matrix adaptation evolutionary strategy algorithm is applied to optimize a dielectric loaded microstrip patch antenna. The optimization process performance is enhanced by not considering the symmetrical factor of the antenna structure. The antenna is optimized to work for IEEE 802.11a WLAN 5-6 GHz band. Experimental measurements have also been performed to validate the performance of the proposed antenna.

This paper presents an analytical solution for capacitance and characteristic impedance of CPW with defected structures (CPW_DS) in signal line. The first category of incomplete elliptic integrals F(φ, k) is employed for calculation, and the capacitance and characteristic impedance of CPW_GS in signal line are first time achieved by the analytical solution. FEM simulation results are used toverify the results of analytical solution,which shows a good agreement. All calculations are completed in software Wolfram Mathematica, and CPW structures are simulated in software HFSS.

A new method of electrodynamic analysis of gyrotropic (isotropic and anisotropic) media is developed. This method is based on the scalar representation of Maxwell's equations corresponding to 4×4- matrix formulation and coupling equations for gyrotropic medium in the Drude's form. It is utilized by solving the wave equations of second and fourth order, followed by cross-linking the fields at the boundary. The obtained results are experimentally verified by their good matching with the popular benchmark data, such as quartz rotatory power and in comparison with a known standard parameter of an optical element, such as λ/4-plate. This method simply summarizes the polarimetric and ellipsometric calculations.

A novel ultra-wideband (UWB) coupled-line coupler with an operating frequency band from 2 to 22 GHz is presented in this article. The proposed coupler is composed of six coupled-line sections. The continuous zigzag capacitive compensation (CZCC) technology is used to broaden the operation frequency band, which also significantly enhances the isolation and return losses of the coupler. The coupler is built on a multilayer circuit structure. In order to improve the design accuracy of the three-dimensional circuit structure, the combination simulation of EM simulator and circuit simulator are employed. The simulated and measured results of the UWB 10 dB asymmetric directional coupler are presented and discussed, which demonstrate that it is practical to achieve good performances in such a circuit structure.

Two novel microstrip MIMO antennas have been proposed and presented in this paper. The objective is to design a compact and dual-broadband MIMO antenna module appropriate for many wireless devices including WLAN, LTE and WiMax. The presented MIMO antennas have been analyzed, designed, simulated and investigated using CST_MW simulator. They have been fabricated (FR-4 substrate), and their scattering matrices and total efficiencies have been measured. The first MIMO antenna module is composed of four proposed broadband microstrip antennas arranged in two MIMO antenna pairs. The first MIMO pair resonates at 5.2 GHz (5.08-5.313 GHz) while the second pair resonates at 5.8 GHz (5.643-5.96 GHz). This MIMO antenna has a compact size of 40x40 mm², dual-broadband, minimum mutual coupling below -25 dB, bandwidth greater than 225 MHz and gain of 3.8 dBi. The second MIMO antenna module consists of two proposed and modified dual-broadband microstrip monopole antennas, where, each has a dual resonance at 3.7 GHz (3.46-3.94 GHz) and 5.2 GHz (4.99-5.41 GHz). This MIMO antenna has an overall compact size of 20x50 mm², minimum coupling below -22 dB, bandwidth greater than 425 MHz and gain of 2.5 dBi. Good agreement has been achieved between measured and simulated results. The proposed MIMO antennas cover many wireless applications with the following specifications: compact size, dual-broadband, moderate gain, good efficiency and high port-to-port isolation.

A broadband circularly polarized planar antenna based on a quarter-mode substrate integrated cylindrical cavity subarray is presented in this communication. It is composed of two layers: a quarter-mode substrate integrated cylindrical Cavity (QMSICC) subarray and the feeding network comprised of three Wilkinson power dividers. The measured 10-dB return loss and 3-dB axial ratio bandwidths at the center frequency 5.2 GHz are 40% and 25.5%, respectively. The gain measured for right-hand circular polarization (RHCP) is 4.6 dBi at 5.2 GHz. And it will be used in WLAN operating at 5.2 GHz.

A novel microstrip tri-band bandpass filter is proposed and implemented using hybrid resonator with independently controllable center frequencies and good in-between isolation. This hybrid resonator is constructed by a stepped-impedance stub resonator and a single end shorted resonator. The stepped-impedance stub resonators are applied to achieve the first and second passband, while the third passband is implemented by single end shorted resonators. By applying the even-odd mode approach, the resonance frequency ratio between even mode and odd mode inside the stepped-impedance stub resonators is attained. Furthermore, the filter with multi-path coupling structure can generate the transmission zeros at the edge of the passband, which can effectively improve the filter passband selectivity. Finally, a tri-band filter operating at 1.91, 2.73, and 3.45 GHz is designed and fabricated. The measurement results accord well with the full-wave electromagnetic designed responses.

Underestimation of path loss when planning the deployment of 802.11n APs can lead to coverage gaps and user dissatisfaction. The use of Free Space Path Loss modelling can sometimes lead to underestimation of path loss in urban environments when the effect of small scale fading is not considered. A field experiment was conducted with the aim to investigate the applicability of the ITU-R P.1141-7 Recommendation in path loss estimation of 802.11n signals in an urban environment in Malaysia. The results showed that Section 4.3 of ITU-R P.1411-7 can estimate the path loss of 802.11n signals with very low error margins of between 0 dB and 5 dB for transmitter receiver distances of 50 m and more. At these distances, the average difference of path loss estimation between FSPL and measured path loss is approximately 18 dB. The study concludes that 802.11n APs may need to be placed at closer proximities than previously assumed if FSPL is used to model the path loss. This is to ensure that targeted traffic is actually offloaded; coverage gaps are reduced; user satisfaction is improved.