In this paper, a dual-band Substrate Integrated Waveguide (SIW) resonator with Sierpinski fractal geometry is proposed. The space-filling property of the employed fractal shape allows to reduce the resonator size. The bandwidth, the minimum insertion loss, the maximum return loss and the stop band rejection are considered for evaluating the effect of the fractal geometry on the resonator characteristics. An accurate electromagnetic investigation is made using a full wave finite element method solver (Ansoft HFSS). Simulated and measured results are in good agreement. The second iteration fractal resonator exhibits two simulated bands centered at the frequencies f₁=11.57 GHz and f₂=25.7 GHz, while the measured frequencies are f₁=11.33 GHz, f₂=23.67 GHz. The measured bandwidths are BW=1.15 GHz and BW=2 GHz and the minimum insertion losses are close to -1.36 dB and -1.97 dB, respectively. The prototypes of the square resonator without, with first and with second iteration fractal geometry are fabricated via standard printed circuit board process (PCB). A Rogers Duroid 5880 substrate with thickness t=0.381 mm is employed.

The concept of Scattering-Induced Mutual Coupling Effect (SIMCE) is proposed, and the mechanism of producing this phenomenon in Multiple-Input Multiple-Output (MIMO) communication systems at MilliMeter Wave (MMW) band is demonstrated. The model of estimating the scattering-induced mutual impedance in rain environment is derived, and the characteristics of Rain-Induced Scattering Mutual Impedance (RISMI) are discussed taking parabolic antennas as an example. The model of estimating the rain-induced mutual impedance is helpful for investigating the SIMCE in other discrete random media. And, the results given in this paper are significant for developing MMW MIMO communication systems.

This paper presents an effective joint range-DOA-frequency (JRDF) estimation method based on fourth-order cumulants for multiple mixed near-field sources and far-field sources impinging on a symmetric uniform linear array, named as JRDF algorithm. Making use of the proposed method, range-DOA-frequency can be effectively estimated by the same eigen-pair of a defined ``information matrix'' constructed by two fourth-order cumulant matrices. Compared with the related works, the proposed method can provide superior performance, such as higher estimation accuracy, without the procedure of parameter search or parameter matching. Simulation results are presented to demonstrate the efficacy of the proposed approach.

Based on the Collins integral formula and Lohmann optical system, we expand the hard edge aperture into complex Gauss function and derive an approximate analytic expression of intensity distribution theoretically for Hypergeometric-Gauss beams through the fractional Fourier transform (FRT) optical systems with hard edge aperture. The influences of FRT order, aperture size and other optical parameters on the light intensity distribution of Hypergeometric-Gauss beams passing through the FRT optical systems are discussed in detail. The results show that the FRT is an excellent beam-shaping method.

We have studied the instability of electrostatic ion-cyclotron waves in collisional magnetized two-ion component plasma (light positive K⁺ ions and heavy positive Cs⁺ ions). An ion beam propagating through collisional magnetized plasma containing electrons and two positive ion components drives electrostatic ion cyclotron (EIC) waves to instability via Cerenkov interaction. Analytical expressions & numerical calculations have been carried out for the frequency and growth rate of ion cyclotron waves for two EIC wave modes for existing experimental parameters, and it is found that the unstable mode frequency does not depend on electron collision frequency, while the growth rate is increased linearly with the electron collision frequency. Moreover, as the light ion concentration is increased, the frequency of the heavy ion mode moves closer to its gyrofrequency. Similarly, the frequency of the light ion mode approaches the light ion cyclotron frequency as the heavy ion concentration is increased. It is also found that the normalized unstable mode frequencies remains unchanged with electron collision frequencies, while the growth rate is increased linearly with the electron collision frequencies. In addition, the unstable mode frequencies are found to be dependent on the magnetic field strengths.

In this paper, a compact microstrip fed ultra-wideband antenna with a band notch characteristic is presented. The proposed antenna consists of two tridents and two uneven split ring resonators. The overall size of the antenna is 26 mm × 24 mm × 1.53 mm. By adding the uneven split ring resonators to the dual trident ultra-wideband antenna, a band notch of 5.05 GHz to 5.9 GHz is achieved. The band notch is adjusted by the size and the split locations of the resonators. CST microwave studios software was used to simulate the design. The measured |S₁₁| (dB) pass band and notch band agree with the simulation within the frequency band from 3.65 GHz to 12.85 GHz.

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.