In the present paper the analysis of notch loaded shorted half disk patch is given. It is found that the bandwidth of the antenna depends inversely on the notch width whereas it is invariant with the notch length. Further antenna shows dual band behavior for a gap spacing below 7.5 mm in the gap coupled half disk shorted patch whereas it behaves as a wideband antenna for gap spacing more than 7.5 mm. Theoretical results are compared with simulated and experimental results.

In this work a new robust adaptive digital beamforming algorithm called Gaussian Robust Capon Beamformer (GRCB) is proposed, it is based on conventional Capon criteria and provides compensation of the steering vector errors through diagonal loading approach. This research was conducted assuming a critical scenario where a communication environment presents a high value of angular spread (AS >2 degrees) on signal of interest and in which other beamforming methods, including robust Capon algorithm, can degrade their performance upon presenting the phenomenon of auto-cancellation of the signal of interest. Additionally, is discussed a study of the beamforming algorithms performance, based on Minimum Variance Distortionless Response (MVDR) method as well as its robust version; this study is conducted using a radio channel model with a Gaussian scatters distribution, around the signal of interest and typical angular spread values for different mobile communication environments. Finally, simulations results are shown where the performance of GRCB algorithm is compared with different approaches of Capon beamforming, can be observe that using the proposed algorithm is possible to achieve a minimization in signal of interest degradation and a better isolation, regardless of interferers and noise levels.

The diffraction by a semi-infinite parallel-plate waveguide with sinusoidal wall corrugation is analyzed for the H-polarized plane wave incidence using the Wiener-Hopf technique combined with the perturbation method. Introducing the Fourier transform for the unknown scattered field and applying an approximate boundary condition together with a perturbation series expansion of the scattered field, the problem is formulated in terms of the zero-order and first-order simultaneous Wiener-Hopf equations. The Wiener-Hopf equations are solved via the factorization and decomposition procedure leading to the exact solutions. Explicit expressions of the scattered field inside and outside the waveguide are derived analytically by taking the inverse Fourier transform and applying the saddle point method. Far field scattering characteristics of the waveguide are discussed in detail via representative numerical examples.

A new integration technique based on use of Quasi Monte Carlo Integration (QMCI) technique is proposed for Method of Moments (MoM) solution of Integral equation for capacitance computation. The integral equation for unknown charge distribution over the capacitors is formulated. The solutions are obtained by MoM using the QMCI technique. It is observed that the proposed method is not only capable of dealing with the problem of singularity encountered in the Integral Equation efficiently but also provides accurate computation of the capacitances of parallel plate, cylindrical and spherical capacitors.

In this paper, a novel corrugated structure at the edges of the Vivaldi substrate is presented. Compared with the Vivaldi antenna without corrugated structure, the new structure has a better radiation pattern. While compared with the traditional corrugated structure, the new structure has a better front-to-back ratio (F/B ratio). Properly chosen thickness and dielectric constant of substrate ensure a relatively small size while the lower frequency is around 1 GHz. A Vivaldi structure also promises high gain in ultra-wideband (UWB) range. For its planar structure, the antenna is easily fabricated with a low cost. The design of a novel Vivaldi antenna described in this paper operates from 1 GHz to more than 3 GHz with -10 dB return loss and produce the gain with a range of 7 dBi~11 dBi. The current design is one of the most ideal antennas to be used for through-wall radar.

In this paper we present the design of a novel Patch Antenna with Switchable V-Slot (PASVS) that resonates at two different frequencies. The antenna operates at the lower frequency when the switch is OFF and at the higher frequency when the switch is ON. This antenna is designed for special applictions which need small frequency ratio. The different effects of the feeding position, the slot location, and the slot length are invetigated in this paper. This investigation has been used to optimize the design of the PASVS antenna in terms of the return loss (RL), the bandwidth, the gain, and the required frequency ratio.

A systematic method for the diagnosis of planar antenna arrays from far field radiation pattern using neural networks is presented. Two types of neural networks, Radial basis function (RBF) and Probabilistic neural network (PNN) are considered for the performance comparison. Deviation pattern is used as input to the neural network to determine the location of the faulty element and error in excitation.

A novel scheme for detecting the location of a metallic mine (modeled as a perfectly conducting sphere and spheroid) in marine environment is presented. This technique takes into account Eddy-Current response (ECR) induced on the conducting marine mines as well as Current-Channeling response (CCR) associated with the perturbation of currents induced in the conductive marine environment. It leverages on the unique electromotive force (EMF) induced in a receiving coil through different orientations of a transmitting coil with respect to the marine mine. Unlike conventional EM sensing apparatus which is used to carry out the measurement at just one attitude at a fixed angle with respect to buried mine, our proposed scheme consists of angular scanning via the symmetry axes of a concentric sensor over the metallic mine in order to obtain a unique normalized induced voltage determining the mine's depth. Simulated results show that this technique has the potential of extending the depth detection range compared with the current method especially in conductive marine environment up to about 2 meters away from the sensor.

An analytical investigation has been presented of Au nano- coated dielectric optical fibers. The propagation constants of different transverse TE and hybrid EH modes are obtained corresponding to varying nano-coating thickness. It has been observed that the Au-layer has its profound effect on the number of propagating modes in the fiber, and the number of sustained modes is much reduced with the increase in Au-layer thickness. For the sake of comparative investigation, the modal behavior of three-layer dielectric fibers is also taken into account together with the Au nano-coated four-layer fiber. It is reported that the Au-layer has the effect of mode proliferation with simultaneous reduction in their propagation constant values.

Full-duplex radio-over-fiber (ROF) transport systems based on distributed feedback laser diode (DFB LD) with main and -1 side modes injection-locked technique is proposed and demonstrated. Improved performances of bit error rate (BER) over a-40 km single-mode fiber (SMF) transmission for down-link, and over an-80 km SMF transmission for up-link were achieved. The characteristic of our proposed systems is the use of one DFB LD with main and -1 side modes injection-locked technique, it reveals a prominent alternative with better performances.

In this paper, a 3-dimensional metamaterial absorber operating at 11.8 GHz was presented. The metamaterial absorber is composed of coplanar magnetic and electric resonators, with the latter in the center part of the former. By carefully adjusting structural dimensions of magnetic and electric resonators, absorbance per unit cell can reach up to 96% at 11.8 GHz with a 6% FWHM (Full Width at Half Maximum). The full-wave simulations confirmed nearly equal permeability and permittivity and large imaginary part of the refractive index at 11.8 GHz and thus proved the effectiveness of the proposed 3-dimensional metamaterial absorber for microwave applications.

A full-duplex radio-over-fiber (ROF) transport system employing semiconductor optical amplifier (SOA)-based optical single sideband (SSB) modulation technique is proposed and demonstrated. For our proposed approach, it is relatively simple to implement as it requires only one SOA to generate optical SSB signal. Over an-80 km single-mode fiber (SMF) transmission, low bit error rate (BER), clear eye diagram, and low third-order intermodulation distortion to carrier ratio (IMD₃/C) were achieved. Our proposed full-duplex ROF transport systems are suitable for the long-haul microwave optical links.

A direct 61 GHz demodulator, based on a rectangular waveguide (WR-12) six-port, is presented in this letter. The six-port device, composed of four 90° hybrid couplers fabricated in a metal block of brass, is implemented in ADS software. Good agreement between QPSK demodulation results using an ideal six-port model and a second one, based on the S-parameter measurements of a 61 GHz hybrid coupler, is achieved.

A hemisphere dielectric resonator pattern reconfigurable antenna (DRA) is proposed in this paper. The proposed antenna element can operate in four states (SI~SIV) and correspondingly reconfigures its patterns in four directions. A thinning linear array by non-uniform spacing with the element is constructed to scan its main beam from θ=-77^o to 77^o in E-plane with 3-dB beam coverage from θ=-90^o to 90^o by changing two states and progressive phases.

3.5 GHz fixed wireless access system is a point-to-multipoint wireless technology providing broadband services. In this paper, point-to-multipoint fixed cellular service network structure such as Local Multipoint Distribution (LMDS) service is proposed to share same network area and frequency band (3400-3600 MHz) with the fourth generation of mobile (IMT-Advanced) represented by mobile Worldwide Interoperability for Microwave Access (WiMAX) service on base of co-sited systems. As a result of space and frequency domain sharing, harmful interference probability may be transpired between the two services. Different network cell size and different channel bandwidths were considered in dense urban area to investigate the intersystem interference effects based on the average interference to noise ratio INR as a fundamental criterion for coexistence and sharing coordination between different systems. Adjusting of antenna discrimination loss is also proposed to facilitate the frequency efficiency and accomplish frequency sharing.

This paper describes the design of the disk-loaded monopole with a parasitic array for beam switching. Usually the radiation pattern of a single element such as a λ/4 monopole and the disk-loaded monopole provide low values of gain. The beamwidth is normally large and the coverage is wide. This may be appropriate in an on-body channel where the antenna orientation may not be easily controlled, such as when the users put the terminal in their pocket. In some non-body applications such as WLAN, it is necessary to design antennas with high gain to meet other demands such as high capacity or long range. Also, in the on-body environment it is essential to have such gain in order to minimize the path loss between the antennas, and hence increase the battery life. The antenna was excited using coaxial cable produced more gain and pattern compared to the single element top disk-loaded antenna. The reduced-size antenna namely a sector antenna array also has been discussed in detail in this paper. Such design has allowed at least 50% of the size reduction. The simulation results have shown very good agreement with the measurement for both antennas.

A comparison between different modern population based optimization methods applied to the design of scannable circular antenna arrays is presented in this paper. This design of scannable circular arrays considers the optimization of the amplitude and phase excitations across the antenna elements to operate with optimal performance in the whole azimuth plane (360^ο). Simulation results for scannable circular arrays with the amplitude and phase excitation optimized by genetic algorithms, particle swarm optimization and the differential evolution method are provided. Furthermore, in order to set which design case could provide a better performance in terms of the side lobe level and the directivity, a comparative analysis of the performance of the optimized designs with the case of conventional progressive phase excitation is achieved. Simulation results show that differential evolution and particle swarm optimization have similar performances and both of them had better performance compared to genetic algorithms when all algorithms are allowed equal computation time.

The Goos-Hachen (GH) shift at the surface of chiral negative refractive media is analyzed theoretically. GH shifts are observed for both perpendicular and parallel components of the reflected field near the respective critical angles. It is found that positive and negative shifts can be attained when the incident angle is larger than the first critical angle, whereas if the angle of incidence exceeds the second critical angle, only positive shifts can be observed. In addition, a Gaussian beam is further adopted to illustrate the effect of the GH shifts.

A circuit theory-based approach for systematically deriving all possible lossless balanced composite right/left-handed transmission lines is described. To illustrate the usefulness of the proposed approach, novel artificial transmission line unit-cells with tri- and quad-band behaviour are proposed. It is shown that the number of right-handed or left-handed frequency bands exhibited by such transmission lines is determined by the order of its unit-cell. It is explained why artificial lossless balanced transmission lines exhibit a stop-band around each pole of their associated continuous transmission line that can not be closed up. Since this approach allows for the systematic derivation of such transmission line unit-cells of arbitrary order, multi-band components based on metamaterial transmission lines are envisaged.

Practical interests arising from behind-the-wall target detection, surveillance and reconnaissance et al. claim for high capability of imaging in complicated environments. Time Reversal Mirror (TRM) technique, making use of the principle of reciprocity, emerges as a promising way to deal with such complex problem. In this paper, we investigate TRM in the ultra-wideband (UWB) through wall radar imaging (TWRI) through numerical simulation. The probing region is a square room, with walls of rough surface and random media parameters. TRM is used to image the target settled in the room. We evaluate the degradation of the images when the aperture of the array is decreased or the received signals are contaminated by noises. The back projection (BP) algorithm is employed here as a comparison for imaging quality. For the case in which the random walls are changed between the forward and inverse phase of time reversal, we check the imaging stability and applied an averaged Green's function to improve the imaging quality. Finally, some interesting conclusions are drawn.