A dual-band multifunction hybrid antenna for carborne satellite communication relay system is presented in this paper. As a consequence of the radiation requirements, the proposed antenna consists of a left-hand circularly polarized (LHCP) microstrip patch and an omnidirectional biconical antenna with a conductor tube holding and radome. The LHCP microstrip antenna is used for satellite signal reception, and bionical antenna is used for relay communication transmission. A novel overmoded coaxial waveguide feed structure eliminates the interference between two feed ports. The proposed antenna has the advantages of robustness, low cost, and easy fabrication with conventional materials and printed circuit technology. An antenna prototype is fabricated to validate the design. Both the simulated and measured results are obtained with reasonable agreement.

In this paper, jerk function for a transient process of RL circuit is investigated. Some new concepts such as time rate of change of induced emf, time rate of change of displacement current, and Appell function have been introduced for the first time in electromagnetic jerky dynamics. The problems on Appell function of several simple models in electromagnetic jerky dynamics are discussed. In the last conclusions and remarks are also presented.

This paper presents some improved analytical expressions of the magnetic field produced by arc-shaped permanent magnets whose polarization is radial with the amperian current model. First, we show that the radial component of the magnetic field produced by a ring permanent magnet whose polarization is radial can be expressed in terms of elliptic integrals. Such an expression is useful for optimization purposes. We also present a semi-analytical expression of the axial component produced by the same configuration. For this component, we discuss the terms that are difficult to integrate analytically and compare our expression with the one established by Furlani [1]. In the second part of this paper, we use the amperian current model for calculating the magnetic field produced by a tile permanent magnet radially magnetized. This method was in fact still employed by Furlani for calculating the magnetic field produced by radially polarized cylinders. We show that it is possible to obtain a fully analytical expression of the radial component based on elliptic integrals. In addition, we show that the amperian current model allows us to obtain a fully analytical expression of the azimuthal component. All the expressions determined in this paper are compared with the ones established by Furlani or in previous works carried out by the authors.

An all-dielectric composite route is proposed for the construction of a left-handed material at THz frequency. It is shown that the interaction between the crystal lattice vibration of the polaritonic dielectric and the electromagnetic wave could induce a negative permittivity. By combining the electric inclusion of polaritonic dielectric with the magnetic inclusion based on Mie resonance, the dielectric composite exhibits simultaneously negative permittivity and negative permeability, hence a negative refractive index. Additionally, the simulation results of the electromagnetic coupling between the electric and magnetic inclusions indicate that the behavior of the negative refractive index is closely related to the distance between the two inclusions.

A compact dual-band annular-ring slot antenna (ARSA) is proposed for use in 2.4/5 GHz wireless local-area networks (WLANs). With a meandered grounded strip embedded in the ring slot, three resonant modes were excited. With a pair of notches properly etched in the inner circular patch, the third resonant band was sufficiently lowered so that the second and third resonant bands are combined to form a wider upper operating band. If scaled to the same lower operating-band center frequency, the proposed ARSA measures only 53.6% the area of a conventional microstrip-line-fed ARSA. Measured and simulated results were found to agree reasonably well with each other.

Based on the use of micro electro-mechanical system (MEMS) switches this paper presents a composite right/left-handed (CRLH) transmission line (TL) with a reconfigurable behaviour. The design strategy here adopted consists on the use of metal-insulator-metal (MIM) capacitors and short-circuited stubs resulting in a very compact and monolithic CRLH unit cell well suited for phase shifter applications.

A novel circularly polarised (CP), single-fed widebeam microstrip antenna is presented. The antenna consists of a corner-truncated square patch and a three dimensional circular ground structure. Simulated and measured results show that, owing to the ground structure, the 3 dB beamwidth of the CP radiation can reach more than 165^o, which is about 85^o, greater than that of a corresponding regular microstrip antenna. It is also shown that experimental results were in good agreement with the simulated performance. Details of the proposed 3-D circular ground structure are described, and the effects of various dimensions of the proposed ground structure on the beamwidth enhancement of CP radiation are studied.

This paper addresses the sensor selection problem which is a very important issue where many sensors are available to track a target. In this problem, we need to select an appropriate group of sensors at each time to perform tracking in a wireless sensor network (WSN). As the theoretical tracking performance is bounded by posterior Cramer-Rao lower bound (PCRLB), it is used as a criterion to select sensors. Based on the PCRLB, sensor selection algorithms with and without sensing range constraint are developed. Without sensing range limit, exhaustive enumeration is first adopted to search all possible combinations for sensor selection. To reduce complexity of enumeration, second, we restrict the selected sensors to be within a fixed area in the WSN. With sensing range constraint, a circle will be drawn with the help of communication range for sensor selection. In a similar manner, two approaches, namely, selecting all sensors inside the circle or using enumeration to select sensors within the circle are presented. The effectiveness of the proposed methods is validated by computer simulation results in target tracking for WSNs.

Modern electronic products are increasingly based on high-speed, high-density circuitry operating at lower voltages. With such designs, the signal integrity (SI) in a poor printed circuit board layout is affected by noise and may become unstable. Crosstalk is a major source of noise that interferes with SI. Generally, crosstalk can be reduced by adding a guard trace between the victim and aggressor areas of the circuit. In addition, grounded vias can be added to the guard trace to help reduce crosstalk. Since a large number of grounded vias degrade the SI and reduce the flexibility of the circuit routing, we propose a method to calculate the optimal distance between grounded vias in the guard trace and determine the smallest number of vias required to achieve optimal performance in reducing crosstalk. We show by time-domain simulation that our method reduces the near-end crosstalk by 27.65% and the far-end crosstalk by more than 31.63% compared to the three-width rule. This is backed up by experimental results that show not only reductions of 34.49% and 37.55% for the near- and far-end crosstalk over time-domain, respectively, but also reductions of 2.1 dB and 3.3 dB for the near- and far-end crosstalk over the frequency-domain, respectively. Our results indicate that our method of optimal grounded vias has better performance than other methods.

An accurate and efficient formulation is presented for the electromagnetic analysis of dielectric waveguide gratings under plane-wave conical incidence. An arbitrary number of dielectric bars can be placed inside each one-dimension periodic cell, including the effect of dielectric losses. The reflectance of a dielectric waveguide grating under conical incidence is compared with theoretical results presented by other authors, finding a very good agreement. A single-layer reflection filter has been designed centered at λ₀=1.5 μm whose spectral and angular responses are shown. For this structure, the effect of the asymmetry of the distribution of the refraction index in the reflectance has been analyzed, observing a splitting of the reflection peak around the design wavelength. Finally it is discussed the equivalence between a volume grating and a shallow surface-relief grating, providing two examples of designing prescriptions.

In this paper, we study the bistatic reflection and transmission properties of random rough surface with large slope and large height. Method of Moment (MOM) is used to solve the surface integral equations for 2D rough surface scattering problem. The modeled rough surfaces are similar to random rectangular grating, so that there are large slopes on the surface. The motivation of the study is to analyze scattering by sastrugi surface in Polar Regions. The ridges on the sastrugi surface have heights of about 20 cm. In microwave remote sensing of land at 5 GHz, 10 GHz, 19 GHz and 37 GHz, these heights are larger than wavelength. Next, we consider the scattering problem of the sastrugi rough surface over multi-layered snow. The bistatic reflection and transmission coefficients from MOM solutions are used as the boundary conditions for multi-layered radiative transfer equations. The radiative transfer equations are solved and the reflectivities are calculated. Numerical results are illustrated as a function of roughness and multi-layered parameters. We demonstrate that rough surface of sastugi, when interactions with layered media, causes increase in reflectivity and the decrease in emissivity. The increase of reflectivity can be attributed to the fact that rough surface with large slope facilitates large angle transmission. The large angle transmission results in increase of subsurface reflection and the possibility of total internal reflection in layered media below the rough surface.

A method based on plant growth simulation algorithm (PGSA) is presented for pattern nulling by controlling only the element amplitudes of linear antenna array. The PGSA is a new and highly efficient random search algorithm inspired by the growth process of plant phototropism. Simulation results for Chebyshev patterns with the imposed single, multiple and broad nulls are given to show the performance of the proposed method.

A planar, circular monopole antenna (PCMA) with satisfactory radiation characteristics over an ultra-broadband is demonstrated. Compared to the classical coplanar-waveguide (CPW) fed PCMA, the radiation characteristics of the proposed CPW-fed PCMA are significantly improved, particularly at the frequencies around the higher band edge. This improvement is achieved by exploiting a tapered and periodically corrugated edge design to the CPW ground plane. The tapered and corrugated ground-plane edge design, in essence, modifies the current distribution on the circular disc as well as along the edges of the ground plane. With this design, the cross polarization radiation is remarkably reduced, and the pattern deterioration, especially at the planes perpendicular to the plane of the antenna, is greatly alleviated. The demonstrated CPW-fed PCMA features an over 150 % VSWR=2 fractional bandwidth (0.81-5.87 GHz) and promises satisfactory radiation characteristics over the entire band. The proposed PCMA is poised for applications in wideband/ultra-wideband communication systems.

In this paper, the conformal finite-difference time-domain (CFDTD) method using PSO optimization is applied to design a compact directive balanced antipodal Vivaldi antenna for ultra-wideband (UWB) applications. This paper demonstrates miniaturized antipodal Vivaldi antenna (32 × 35 × 1.6 mm³), having low-cross polarization levels and reasonable gain from 3.1 to 10.6 GHz. The antenna peak gain is 5.25 dBi in the specified band. The simulated and experimental results of return loss, far field patterns and gain are presented.

We provide here a theoretical description of electromagnetic scattering by multi-wall carbon nanotubes based on an effective-boundary condition derived previously using a phenomenological quantum model. We present the basic analytical solution, extending it then to include the electromangetic interaction between multiple concentric tubes in the general multi-wall carbon nanotube case.

The design, simulation and performance enhancement of a new structure for X-band high-power, low-loss, low-bias, triangular-ferrite waveguide circulator are presented. Dual circulation property is obtained by triangular shape of ferrite post. The effects of circulator's structure parameters, such as ferrite parameters and magnetic DC bias, on isolation, insertion loss and return loss of circulator are discussed. The HFSS software is used for simulating the circulators. Final dual band designs with 20 dB return loss, 20 dB isolation and 0:1 dB insertion loss in dual frequency in X-band (8:2 GHz and 10:4 GHz) with only a magnetic bias of 10 Oe are obtained.

Multiple-input multiple-output (MIMO) systems play a vital role in fourth generation wireless systems to provide advanced data rate. In this paper, a better performance and reduced complexity channel estimation method is proposed for MIMO systems based on matrix factorization. This technique is applied on training based least squares (LS) channel estimation for performance improvement. Experimentation results indicate that the proposed method not only alleviates the performance of MIMO channel estimation but also significantly reduces the complexity caused by matrix inversion. The performance evaluations are validated through computer simulations using MATLAB® 7.0 in terms of bit error rate (BER). Simulation results show that the BER performance and complexity of the proposed method clearly outperforms the conventional LS channel estimation method.

We report fast and accurate simulations of metamaterial structures constructed with large numbers of unit cells containing split-ring resonators and thin wires. Scattering problems involving various metamaterial walls are formulated rigorously using the electric-field integral equation, discretized with the Rao-Wilton-Glisson basis functions. Resulting dense matrix equations are solved iteratively, where the matrix-vector multiplications are performed efficiently with the multilevel fast multipole algorithm. For rapid solutions at resonance frequencies, convergence of the iterations is accelerated by using robust preconditioning techniques, such as the sparse-approximate-inverse preconditioner. Without resorting to homogenization approximations and periodicity assumptions, we are able to obtain accurate solutions of realistic metamaterial problems discretized with millions of unknowns.

In the present paper notch loaded shorted microstrip patch antenna has been analysed using cavity model. The proposed antenna shows dual band operation which depends on notch dimensions as well as shorting wall. The frequency ratio is found to be 1.5278 for the notch loaded rectangular patch, while in notch loaded shorted patch, the frequency ratio varies from 2.9764 to 2.725 for increasing value of notch width and it is almost invariant with notch depth. Further a slot loaded shorted patch antenna shows the dual frequency nature with the frequency ratio1.7. The theoretical results are compared with IE3D simulation as well as reported experimental results.

By employing Microelectromechanical system (MEMS) technology, Fabry Perot Optical Tunable Filter (FPOTF) with hybrid tuning mechanism, varying d and altering incident angle is presented. The proposed structure consists of a floating dual membrane FPOTF with capability to be tuned at different light incident angles. Three electrostatic cavities have been designed to perform this task independently. This technique is capable to increase the tuning range up to 2/3 of capacitance gap with additional doubly range of incident angle. Optic, mechanic and electrostatic analysis of the proposed structure has been validated by simulation. Analysis in optical performance shows the tuning range enhancement is about 1.92% for +/-2^o mirror tilting at 6^o initial angle compared to conventional dual beam MEMS FPOTF. This analysis validates the principle of hybrid tuning method.