A new method to rapidly design 2D metamaterials for rectangular waveguides by rebuilding their dispersion properties is proposed. The Modal Expansion Theory (MET) is revisited for theoretical surfaces with fixed surface impedances Z_S. Then, it is pursued for real dispersive anisotropic surfaces, which have surface impedances that are dependent on the frequency and the incidence angle. An algorithm which calculates the correct incidence angle of the guided electromagnetic mode at each frequency is presented. By including this algorithm in the MET and by combining it with a code based on the Finite Element Method (FEM) to calculate the surfaces impedances, dispersion diagrams of waveguides with real 2D anisotropic walls are correctly rebuilt. This is validated by comparing the results for two different metamaterials, corrugation- and T-structure, corrugations and metamaterials, with those obtained using a commercial software.

A simple and novel WLAN antenna and a kind of neutralization line, which introduces a certain amount of signal to cancel out the unwanted mutual coupling between two antennas, are designed in this paper. The WLAN antenna working at 2.45 GHz and 5.8 GHz frequency bands is designed, fabricated and measured. The simulated and measured results show that the isolation between the two decoupled antennas can be improved to above 20 dB in both frequencies after decoupling. The lumped match network occupies less space for antennas and gains a good matching performance in the operating frequencies.

A compact fully integrated wideband six-port device composed of a suspended stripline Wilkinson power divider and three bias stripline of 3-dB quadrature directional couplers is presented. In order to integrate the six-port circuit, a multilayer circuit structure has been adopted by the via hole interconnection at the output port of the divider. The 3-dB quadrature directional coupler is composed of two 8.34-dB quadrature directional couplers by series connection. In this way, the six-port circuit structure is simplified and reduced. A multisection impedance match structure has been adopted in the suspended stripline Wilkinson power divider to achieve ultra-wide frequency band. In the experiment, The fully integrated six-port device has obtained good measurement result. It is superior to other present six-port networks in microwave performance with the same dimension.

Radar holography has been established as an effective image reconstruction process by which the measured diffraction pattern across an aperture provides information about a threedimensional target scene of interest. In general, the sampling and reconstruction of radar holographic images are computationally expensive. Imaging can be made more efficient with the use of sparse sampling techniques and appropriate interpolation algorithms. Through extensive simulation and experimentation, we show that simple interpolation of sparsely-sampled target scenes provides a quick and reliable approach to reconstruct sparse datasets for accurate image reconstruction leading to reliable concealed target detection and recognition. For scanning radar applications, data collection time can be drastically reduced through application of sparse sampling. This reduced scan time will typically benefit a real-time system by allowing improvements in processing speed and timeliness of decision-making algorithms. An added advantage is the reduction of required data storage. Experimental holographic data are sparsely sampled over a two-dimensional aperture and reconstructed using numerical interpolation techniques. Extensive experimental evaluation of this new technique of interpolation-based sparse sampling strategies suggests that reduced sampling rates do not degrade the objective quality of holograms of concealed objects.

In this paper, a slot array with a new technique of metamaterial on Electromagnetic Band Gap (EBG) structure is used to demonstrate the possibility of building high gain top-mounted antenna for mobile base station. We describe the method for gain improvement by transferring the electromagnetic fields from a 1×4 slot array with a PEC reflector radiated through the cavity of curved woodpile EBG. The proposed technique not only has the advantages of reducing the total length of the slot array, but also provides higher gain and easier installation. In addition, to provide the azimuth patterns covering 360° around the base station, a triangular array configuration consisting of three panels of such an antenna array has also been presented, while the fabricated cavity of the curved woodpile EBG structure exhibits band gap characteristics at 2.1 GHz for realizing a resonant cavity of the slot array. This idea is verified by comparing between the results from Computer Simulation Technology (CST) software and the experimental results. Finally, it is found that the measured and simulated results are in a good qualitative agreement, and the antenna prototype yields directive gain of each panel around 17.1-17.2 dBi.

This paper presents an active resonant conductance method (ARCM) for the design of large traveling-wave-fed SIW linear slot arrays. Two key slot parameters, slot offsets and lengths, are derived from excitation coefficients with intermediary active resonant conductance. In this method, both dominant mode mutual coupling which includes external & internal and higher order modes mutual coupling are considered. An efficient way to derive active resonant conductance of slots in large slot arrays is proposed, which makes ARCM feasible for the design of large traveling-wave-fed linear slot arrays with high performance, e.g. low sidelobe level (SLL). Finally, a 16-slot and a 32-slot traveling-wave-fed SIW slot array antennas are designed. The processing of the 32-slot array design shows the efficiency of the proposed method for large arrays. The 16-slot array is fabricated and measured. Results from simulation and measurement verify the proposed method.

A novel balanced filter circuit with wideband common mode suppression using coupled lines is proposed in this paper. A wideband filter with half open stubs is used to realize two transmission zeros for the differential mode passband. The common mode can be suppressed over 15 dB from 0 GHz to 3f₀ (f₀ is the center frequency of the passband) with insertion loss greater than 15 dB over the upper stopband. A balanced filter with 3-dB fractional bandwidths of 38% is designed and fabricated. Good agreement can be observed between measured results and theoretical expectations.

Principal component analysis is usually used for clutter suppression of ground penetrating radar, but its performance is influenced by the selection of main components of target signal. In the paper, an improved principal component selection rule is proposed for selecting the main components of target signal. In the method, firstly difference spectrum of singular value is used to extract direct wave and strong target signal, and then, Fuzzy-C means clustering algorithm is used to determine the weights of principal component of weak target signal. Finally, the principal components of strong target signal and weak target signal are reconstructed to obtain target signal. Experimental results show that the proposed method can effectively remove the clutter signals and reserve more target information.

A conductor backed coplanar waveguide (CPW) fed multiband antenna is presented. The shorting of ground in CPW feed and conductor backed arrangement extend the area of ground plane. The proposed antenna consists of rectangular monopole with Complementary Split Ring Resonator (CSRR) engraved in the extended ground plane. The prototype antenna is designed, fabricated and measured. CSRR characteristics are also analyzed. Simulated and measured results of the antenna are in good agreement with each other and are discussed. The proposed antenna can be used for WiMAX, WLAN and RADAR applications at 3.4 GHz, 5.16 GHz and 9.5 GHz, respectively.

We propose an all circular-air-hole short-length polarization beam splitter (PBS) with high extinction ratio based on dual-core highly birefringent photonic crystal fiber (PCF). The impacts of geometrical parameters on the coupling polarization dependence, coupling length ratio (CLR), and propagation property are numerically investigated by the full-vector finite element method (FEM) and the semi-vector beam propagation method (BPM). From simulation results, it is seen that CLRs at the excitation wavelength of 1.55 μm can be optimized to be closed to the desired values of 3/2 and 4/3 to satisfy the sufficient condition of splitting polarized modes by appropriately tailoring the air-hole sizes. For the two optimal structures, the separation of x- and y-polarized modes can be achieved in short lengths of 1.41 mm and 2.89 mm at the operating wavelength of 1.55 μm, respectively. Furthermore, the extinction ratios at λ = 1.55 μm are estimated to be 97.7 dB and 88.1 dB, and the wavelength bandwidths of extinction ratio better than 15 dB are about 107 and 82 nm, respectively.

In this paper, a 3D quasistatic numerical algorithm for computation of the electric field produced by overhead power lines is presented. The real catenary form of the overhead power line phase conductors and shield wires is taken into account with an arbitrary number of straight thin-wire cylindrical segments of active and passive conductors. In order to obtain more precise results of the charge density distribution, segmentation is conducted for each overhead power line span separately. Moreover, the presence of the towers which distort the electric field and significantly reduce its magnitude is taken into account. Therefore, the towers of overhead power lines are approximated using thin-wire cylindrical segments of passive conductors with electric potential equal to zero. From self and mutual coefficients of these components, system of linear equations for computation of the charge density distribution was obtained. In the numerical example, electric field intensity distribution in the vicinity of towers and under the midspan of overhead power lines is shown. In order to verify the accuracy of the presented model, the obtained results are compared with similar published examples and results available in the literature.

The advantages of integrating beamforming Butler matrix in 4×4 Multiple-Input Multiple-Output (MIMO) systems for underground mine wireless communications in the 2.4 GHz band are investigated. To satisfy both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions, two separate measurement campaigns are performed in a real L-shaped underground mine gallery; the first uses 4-elements beamforming conformal microstrip patch arrays (CMPA), while the second uses 4-elements beamforming Butler Network (BN-MIMO) by means of connecting a planar microstrip patch array to a Butler matrix. Due to its high radiation efficiency, the latter shows further performance for enhancing the channel propagation characteristics, and thus, for reducing the average path loss by about (2.2 dB, 5.1 dB) under (LOS, NLOS) conditions, respectively. Similarly, a reduction of (0.67 ns, 3.7 ns) in the RMS delay spread has been achieved to result in an additional gain of (4.6 MHz, 0.82 MHz) in the channel's coherence bandwidth. Furthermore, the orthogonal property of BN array radiation beams has led to a suppression of about (6%, 11%) in inter-subchannels correlations to boost (1.1 bit/s/Hz, 4.35 bit/s/Hz) in the channel capacity.

In this paper, we provide full-wave numerical results concerning the effective magnetic permeability of the rod-shaped ferrites which is useful in the calculation of the inductance or the efficiency of rod antennas. This study concerns the circular cross-section ferrites with a centered winding fitting the diameter of the rod. A careful attention is taken to the simulation model, and obtained results are in better agreement with the measured coils than existing solution published earlier.

A single-layer partially reflective surface (PRS) structure is presented to design single-feed Fabry-Perot resonator antennas (FPRA) with a large gain bandwidth and compact size. The design of the PRS structure applied in this antenna is based on the theory of tightly coupled antenna arrays. Owing to strong mutual coupling between the overlapped patches, the proposed antenna obtains a wider bandwidth and more compact size. Experimental results show that the antenna obtains a 32% 3-dB gain bandwidth from 8.8 GHz to 12.2 GHz, with a peak gain of 13.5 dBi. Moreover, the relative impendence bandwidth is 40.9% for the voltage standing wave ratio (VSWR) less than 2 from 8.45 GHz to 12.8 GHz.

In this paper, two-dimensional (2-D) analytical magnetic field calculations are used to compute crucial quantities of Brushless permanent-magnet (PM) machines with surface-inset PMs. The analytical magnetic field distribution is based on the subdomain technique in which the slotting and tooth-tip effects have been considered. It includes both different magnetization patterns (e.g., radial, parallel and Halbach) and different spatial distribution of winding (e.g., concentrated and distributed with one or more layers). The saturation effect of the magnetic circuit is neglected. In this investigation, the phase and line induced back electromotive force (EMF) waveforms, electromagnetic/cogging/reluctance torques, self-/mutual-inductances and unbalanced magnetic forces (UMFs) have been analytically calculated. The analytical expressions can be used for Brushless machines having surface-inset PMs with any radius-independent magnetization pattern. In this study, two slotted Brushless PM machines with surface-inset PMs have been selected to evaluate the efficacy of the analytical expressions by comparing the results with those obtained by the finite element method (FEM). One of the case studies is a 9-slots/8-poles Brushless DC (BLDC) machine with radially magnetized PMs, non overlapping all teeth wound winding and six-step rectangular armature current waveforms. The other is a 15-slots/4-poles Brushless AC (BLAC) machine with Halbach magnetization PMs, double-layer overlapping winding and sinusoidal armature current waveforms.

The general principles of design and development of microwave absorbing materials are discussed and analysed in respect to 26-37 GHz frequency range (Ka-band). Dispersive composite materials based on carbon nanotubes in epoxy resin matrix are produced, and their electromagnetic responses are investigated in Ka-band. Both theoretical and experimental results demonstrate that presented composites may be used as compact eective absorbers in 26-37 GHz range.

In this paper we develop a higher order extraction method to accelerate the convergence in the computation of broadband Green's function for an arbitrary shaped waveguide. This is applied to a homogeneous waveguide of arbitrary shape. The broadband Green's function is based on modal expansion in which the modal fields are frequency independent. The higher order extraction is obtained by using three low wavenumbers for extraction. It gives a modal expansion of Broadband Green's Function with Low Wavenumber Extraction (BBGFL) with 6th order convergence requiring much fewer evanescent modes for convergence. Numerical results are illustrated for homogeneous waveguides for both lossless and lossy dielectric cases. The accuracy of results are validated with direct method of moment (MoM) and HFSS. The BBGFL method is computationally efficient for broadband simulations.

Wideband circularly polarized antenna is required for many satellite applications. Circularly polarized (CP) Equilateral Triangular-Ring Slot (ETRS) antenna has narrow 3-dB axial ratio bandwidth (ARBW) compared to its impedance bandwidth. Two diagonal line slots were introduced to ETRS for enhancing its 3-dB ARBW. The diagonal line slots were inserted on the left and right side of ETRS. Lengths of the left and right line slots correspond to the lowest and highest frequencies of ETRS antenna 3-dB ARBW, respectively. Both diagonal line slots have successfully improved 3-dB ARBW of ETRS antenna by achieving 680 MHz or 37% fractional bandwidth. Measured results of x-z and y-z planes of radiation patterns also confirm that the antenna has bidirectional radiation and presents good CP performance within its 3-dB ARBW. ETRS antenna RHCP gain is also improved thanks to the diagonal line slots insertion.

A novel capacitive loaded U-slot defected ground structure (DGS) is presented in this letter to provide narrowband rejection property. The principles for the selective rejection and the strategies for size-reduction and external Q-factor improvement are detailed based on transmission line equivalent model and the lumped parallel RLC model developed from transmission line model at resonance frequency. The design concept is well validated by the design and measurement of an exemplary high Q BSF.

The paper presents analytical solution of nonmagnetic and conductive disc levitation problem. The alternating magnetic field exerts eddy currents in conductive disc and levitation force, subsequently. The electromagnetic field and eddy currents distributions are determined. The force acting upon nonmagnetic disc (Lorentz, Maxwell, coenergy methods) and power losses (Joule volume integral, Poynting surface integral methods) are evaluated. For example, levitation force and power losses versus field frequency are figured out. Additionally, an optimization task for power losses at constant disc volume is solved.