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.

In this paper, the hybrid physical optics/boundary integral-finite element-mode matching (PO/BI-FE-MM) method is proposed for the analysis of the horn antenna enclosed by the electrically large radome. The radome is modeled by the PO method, and the BI-FE-MM method is implemented to the horn region. The equivalent PO currents on the radome surface are coupled into the BI-FE-MM equation of the horn region to account for the effects of the radome on the horn. With this hybrid method, the mutual interactions between the radome and the horn are fully considered. The radiation patterns, field distributions, and the S-parameters of the horns enclosed by different kinds of radome are presented.

In this paper, an improved residual carrier frequency offset estimation scheme is proposed for ultra-wideband multiband orthogonal frequency division multiplexing (UWB-OFDM) systems. The basic idea of our approach is based on the fact that two adjacent OFDM symbols convey identical information in an UWB-OFDM system. The mean square error of the synchronization scheme is derived, and its simple expression is also calculated. Finally, simulation results are demonstrated to verify the theoretical analysis in this paper.

The reflection and transmission coefficients of multilayer structures are computed by the Transmission Line Transfer Matrix Method (TLTMM) and it is shown that metamaterials (MTMs) act as frequency selective surfaces (FSSs). Several examples of multilayer structures are analyzed, which are composed of combination of common materials and MTMs with dispersion relations. Interesting and uncommon behaviors are observed for MTMs. Novel applications are treated by TLTMM and a matrix method.

This paper suggests a new method for designing of planar eight port waveguide mono-pulse comparator. Planar eight port waveguide mono-pulse comparator acts as a four-way in-phase power divider in a transmitting mode and as a mono-pulse sum and difference combining hybrid in the receiving mode. The short-slot directional coupler is converted to an equivalent magic tee by adding dielectric-slab-filled waveguide phase shifter. Four such hybrids are connected appropriately using H-plane bends to form a compact planar eight port waveguide mono-pulse comparator. Simulation results with Ansoft HFSS software are presented, which verify good performance.

In this paper, a new route for the realization of left-handed metamaterials (LHMs) is suggested. It is based on commercially available dielectric resonators with low loss and high temperature stability. By etching simple metallic strips on surface of dielectric resonators, the desired resonance modes can be enhanced while the undesired suppressed. In this way, resonance frequency of desired resonance modes can be tuned to the frequency range of interest. As a typical example, a wide-angle polarization-independent planar LHM based on disk-like dielectric resonators is proposed. Negative permeability and permittivity are realized by etching metallic strips along the electric field orientations of TE01_δ and HEM11_δ modes, respectively.

A study is made of the excitation of electromagnetic waves by spatially bounded, arbitrary sources in the presence of a cylindrical guiding structure immersed in an infinitely extended, homogeneous gyrotropic medium whose permittivity and permeability are both describable by tensors with nonzero off-diagonal elements. The axis of symmetry of the considered cylindrical structure is assumed to coincide with the gyrotropic axis. The total field is sought in terms of vector modal solutions of the source-free Maxwell equations. We determine the content of the modal spectrum and obtain an eigenfunction expansion of the source-excited field in terms of discreteand continuous-spectrum modes. The expansion coefficients of the modes are derived in explicit form. An expression for the total power radiated from sources is deduced and analyzed. It is shown that the developed approach makes it possible to readily represent the sourceexcited field without preliminary calculation of the dyadic Green's functions, which significantly facilitates the field evaluation.

A novel compact four element multiple input multiple output (MIMO) antenna is proposed. The antenna is composed of four E-shaped patch elements and operates at 5.8 GHz. The E-shaped patch antenna, operate at this frequency is designed using the Invasive Weed optimization algorithm. This algorithm is then applied to design the two and the four element MIMO antenna for high degree of isolation. In order to measure the array performance under MIMO signaling conditions a multi-port metric is used to characterize the compact array rather than the scattering matrix characterization. The designed antennas have low profile, easy fabrication, low cost and good isolation. The simulation and measurement result of reflection coefficient, mutual coupling and radiation pattern is presented.

Electrical capacitance tomography (ECT) is a relatively mature non-invasive imaging technique that attempts to map dielectric permittivity of materials. ECT has become a promising monitoring technique in industrial process tomography especially in fast flow visualization. One of the most challenging tasks in further development of ECT for real applications are the computational aspects of the ECT imaging. Recently 3D ECT has gained interest because of its potential to generate volumetric images. Computational time of image reconstruction in 3D ECT makes it more difficult for real time applications. In this paper we present a robust and computationally efficient 4D image reconstruction algorithm applied to real ECT data. The method takes advantage of temporal correlation between 3D ECT frames to reconstruct movies 4D of dielectric maps, which enhance the noise performance of and its computational efficiency, improves the speed of ECT image reconstruction. The 4D image reconstruction results are presented for experimental data from fast moving object.

Adaptive beamforming, which uses a weight vector to maximize the signal-to-interference-plus-noise ratio (SINR), is often sensitive to estimation error and uncertainty in the parameters, such as direction of arrival (DOA), steering vector and covariance matrix. Robust beamforming attempts to mitigate this sensitivity and diagonal loading in sample covariance matrix can improve the robustness. In this paper, beamformer based on particle filter (PF) is proposed to improve the robustness by optimizing the diagonal loading factor in sample covariance matrix. In the proposed approach, the level of diagonal loading is regarded as a group of particles and optimized using PF. In order to compute the post probability of particles beyond the knowledge of noise, a simplified cost function is derived first. Then, a statistical approach is developed to decide the level of diagonal loading. Finally, simulations with several frequently encountered types of estimation error are conducted. Results show better performance of the proposed beamformer as compared with other typical beamformers using diagonal loading. In particular, the prominent advantage of the proposed approach is that it can perform well even noise and error in the steering vector are unknown.

A fabricated multilayer low-temperature co-fired ceramic (LTCC) delay line (approximate 16λ_g at 9.5 GHz), using 3D meander strip line, is proposed in this paper for the first time. The advanced quasi coaxial ground vias (QCOX-GND vias) are proposed for signal vertical interconnections in this multilayer structure. These technologies obtain good performances in the whole band (9~10 GHz). Measurement results show that, besides low insertion loss and low VSWRs, low time dispersion can be achieved as ≤±0.002 ns, which is very important to a delay line. The more compact size, as 8 mm × 10 mm × 2.37 mm, can also be obtained than other delay line structures.

A dual-band printed dipole antenna with integrated balun feed is given in this paper. First, the fork-shaped slot is etched on the arms of the printed dipole antenna to achieve the dual-band operation with resonances at WLAN bands. The radiating element without balun is optimized and operates at 2.4 GHz (2180-2750 MHz) and 5.2 GHz (5040 MHz-5480 MHz) where return loss is less than -10 dB. In order to further get a lager bandwidth, a modified Marchand balun is introduced for dual-band operation, which can provide two resonances in each band to enhance impedance bandwidth. By co-designing the radiating element with the dual-band balun, an antenna covering 2150-2750 MHz and 5050-6230 MHz has been achieved. The design equations for modified balun have been presented and agreement between calculations and measurements is good.

This paper describes a memory-reduced (MR) compact two-dimensional (2-D) order-marching time-domain (OMTD) method for full-wave analyses. To reduce memory requirements in the OMTD method, the divergence theorem is introduced to obtain a memory-efficient matrix equation. A lossy microstrip line is presented to validate the accuracy and efficiency of our algorithm.

This paper describes a novel dual-band patch antenna on organic magnetic substrate for wireless local area networks (WLAN) wireless communication (at 2.4 and 5 GHz). The dual-band operation is obtained by embedding a pair of L-shaped slots. The magnetic material is adopted because the substrate can reduce the size of antenna 40%, comparing with rectangular microstrip antennas on normal dielectric substrate, and have wider bandwidths for both bands. Details of the proposed antenna design are presented and discussed, which can be a candidate for the requirement of WLAN, operating in 2.4 and 5 GHz.