A novel adaptive Wireless-Fidelity (Wi-Fi) system is the combination of radio frequency identification (RFID) technology, programmable intelligent microcontroller development board (PIDB) and reconfigurable antenna with beam shape characteristics. The system is capable to sustain a Wi-Fi signal adaptively above its threshold level (-81 dBm) within a range up to 100 m across three different buildings with variety indoor environments and floors. It is found that the modified ground reflection model has successfully predicted the total path loss of the test-bay buildings which consist of corridors, several floors and windows. The modified propagation model is extremely crucial in determining the projection and height of reconfigurable antenna to efficiently cover the scattered measurement points across the three buildings. The need of comparable signal strength is compulsory since the signal strength between 2.4 GHz of reconfigurable beam shape antenna and 0.433 GHz of RFID tag is different within the same distance. When reconfigurable beam shape antenna radiates with a minimum gain of 4.85 dBi, the measured signal strength shows that most of the measurement points are below Wi-Fi‟s threshold level which is from -69.001 dBm to -115.4530 dBm. However, the proposed system is able to boost all the signal strength above the threshold level with three different gain of reconfigurable beam shape antenna, 7.2 dBi, 9.9 dBi and 14.64 dBi through the activation of mobile RFID tag at different measurement points at one time. The boosted signal strengths are within the range of -69 dBm to -73.056 dBm. The capability of the mobile RFID tag in producing certain level of signal strength has been successfully exploited as a wireless stimulator for the system to adaptively activate certain PIN diode switches of reconfigurable beam shape antenna in this finding. The proposed system also has a great potential in realizing a new smart antenna system replacing the conventional switching beam array (SBA) antenna.

In this paper, based on different influences of the lattice symmetry, the geometry of dielectric rod, and the structure of unit cell to absolute gaps we propose a so-called three-order-effect method for the construction of two-dimensional (2D) photonic crystals (PCs) with larger absolute gaps. As an example, by means of our approach we fabricate a 2D hexagonal lattice of cylinder with an optimal rod adding at the center of the unit cell, where the absolute gap is larger than that of the PC with similar structure studied by other group previously. On the other hand, we also find that many of the 2D PCs with larger absolute gaps reported previously possess optimal first-order and second-order substructures. Our three-order-effect method would be useful for the design of 2D PCs with larger absolute gaps.

This paper presents an improved approach for the propagation of electromagnetic (EM) fields along a helical hollow waveguide that consists of two bendings in the same direction. In this case, the objective is to develop a mode model for infrared (IR) wave propagation, in order to represent the effect of the radius of the cylinder of the helix and the step's angle on the output fields and the output power transmission. This model enables us to understand more precisely the influence of the step's angle and the radius of the cylinder of the helix on the output results of each section (bending). The output transverse components of the field, the output power transmission and the output power density for all bending are improved by increasing the step's angle or the radius of the cylinder of the helix, especially in the cases of space curved waveguides. This mode model can be a useful tool to improve the output results in all the cases of the helical hollow waveguides with two bendings for industrial and medical regimes.

Simultaneous switching noise (SSN) is a significant problem in high-speed circuits. To minimize its effect and improve the electrical characteristics of circuits such as signal integrity (SI) and power integrity (PI), a novel power plane with planar electromagnetic bandgap (EBG) structure is proposed for SSN suppression in printed circuit boards (PCB) in this paper. In which a kind of improved long bridge is used and the equivalent parallel inductance can be increased significantly. Compared to the typical spiral bridge EBG structure with the same parameters, the long bridge EBG structure will change bandgap into dual-band, with lower center frequency and wider bandwith. The effectiveness and accuracy of this structure are verified by both simulations and measurements.

Early detection of tumor tissue is one of the most significant factors in the successful treatment of breast cancer. Microwave Breast Imaging methods are based on the dielectric contrast between normal and cancerous tissues at microwave frequencies. When the breast is illuminated with a microwave pulse, the dielectric contrast between these tissues can result in reflected backscatter. These reflected signals, containing tumor backscatter, are spatially focused using a beamformer which compensates for attenuation and phase effects as the signal propagates through the breast. The beamformer generates an energy profile of the breast where high energy regions suggest the presence of breast cancer. Data-Adaptive (DA) beamformers, use an approximation of the desired channel response based on the recorded signal data, as opposed to Data-Independent (DI) algorithms which use an assumed channel model. A novel extension of the DA Robust Capon Beamformer (RCB) is presented in this paper which is shown to significantly outperform existing beamformers, particularly in a dielectrically heterogeneous breast. The algorithm is evaluated on three anatomically accurate electromagnetic (EM) breast models with varying amounts of heterogeneity. The novel beamforming algorithm is compared, using a range of performance metrics, against a number of existing beamformers.

Central Force Optimization (CFO) is a new multi-dimensional search metaheuristic based on the metaphor of gravitational kinematics. In this paper, for the first time, the CFO is applied to the optimal design of multilayer microwave absorbers (for normal incidence) in a specific frequency range. Several numerical examples are presented, in which the CFO results are compared with those found by other evolutionary algorithms. It is shown that the CFO results are comparable to those found by the self-adaptive differential evolution (SADE) algorithm and better than those found by particle swarm optimization (PSO) and gravitational search algorithm (GSA).

The memristor theory of Chua [1] provides a connection with the charge and magnetic flux in an electric circuit. We define a similar relation for the electric and magnetic flux densities in electromagnetism. Such an attempt puts forward interesting results. For example, the magnetic charges do not exist in nature however the electric charges behave as the magnetic monopoles in special media. We support our theory with results of the recent experiments on materials named as spin ice.

This paper proposes a novel design criterion for optimal pyramidal horns. According to it, the optimal aperture phase error parameters of a pyramidal horn are determined from the minimization of the horn's lateral surface area. We present two families of curves that illustrate the optimal aperture phase error parameters for frequency and directivity values in the area of practical interest. We also discuss two simple approximate design methods for the calculation of the optimal horn parameters. Comparisons with well-known design methods demonstrate the efficacy of our approach. The proposed criterion produces the lightest horn for a given directivity; as a result its fabrication requires less material compared to other structures. Moreover, the designed horns have smaller aperture area and occupy less space. The present approach is a useful design tool when the size and weight of a pyramidal horn or its manufacturing cost are of concern.

The results of an ultrawideband (UWB) measurement campaign carried out in a Hercules C-130 military cargo airplane are presented. The environment encompasses several metallic surfaces resulting in a large number of multipath components. Path-loss factor n representing the distance dependence of the channel path-loss is calculated for various frequency centers and bandwidths. A path-gain calculation model based on the concept of seperability of distance and frequency variables is proposed and comparison to measurements is given. Furthermore, time dispersion parameters, namely mean excess delay and root mean square (r.m.s.) delay spread are examined and their dependence on transmitter-receiver antennas separation is investigated. A power law is then employed to model the relation between the number of multipath components and the r.m.s delay spread. The temporal correlation between adjacent path amplitudes is found to be negligible. A modified Saleh-Valenzuela model is invoked to describe the clustering of multipaths, where a different power decay factor is used for the rays of the first cluster as opposed to subsequent clusters. Moreover, the Weibull distribution models the small scale channel fading with a lognormally distributed shape parameter. The average values of this parameter imply severe fading conditions. Finally, simulation results of the proposed statistical model are compared to measured data demonstrating reasonable agreement.

Rain attenuation is one of the most crucial factors to be considered in the link budget estimation for microwave satellite communication systems, operating at frequencies above 10 GHz. This paper presents a mathematical model for converting terrestrial rain attenuation data to be used for satellite applications at Ku-band. In the proposed technique, the ITU-R P 618-9, together with a combination of ITU-R P 530-12 and the revised Moupfouma model have been adopted for satellite and terrestrial rain attenuation predictions, respectively. The model has been used for transforming the measured rain attenuation data of some DIGI MINI-LINKS operating at 15 GHz in Malaysia, to be used for MEASAT 2 applications. It was found that the model predictions are fairly reasonable when compared with direct beacon measurements in Malaysia and similar tropical locations. The model will provide a relatively accurate method for transforming the measured terrestrial rain attenuation to be used for satellite applications; and therefore substantially reduce the cost of implementing Earth-satellite links in some tropical regions that have sufficient rain attenuation data for the terrestrial links.

In this paper, a wide-slot triple band antenna fed by a coplanar waveguide (CPW) for WLAN/WiMAX applications is proposed. The antenna mainly comprises a ground with a wide square slot in the center, a rectangular feeding strip and two pairs of planar inverted L strips (PIL) connecting with the slotted ground. By introducing the two pairs of PIL's, three resonant frequencies, 2.4/5.5 GHz for WLAN, and 3.5 GHz for WiMAX, are excited. Prototypes of the antenna are fabricated and tested. The simulated and measured results show that the proposed antenna has three good impedance bandwidths (S11 better than -10 dB) of 300 MHz (about 12.6% centered at 2.39 GHz), 280 MHz (about 8% centered at 3.49 GHz) and 790 MHz (about 14.5% centered at 5.43 GHz), which make it easily cover the required bandwidths for WLAN band (2.4--2.48 GHz, 5.15--5.35 GHz, and 5.725--5.825 GHz) and WiMAX (3.4--3.6 GHz) applications. Moreover, the obtained radiation patterns demonstrate that the proposed antenna has figure-eight patterns in E-plane, and is omni-directional in H-plane. The gains of the antenna at operation bands are stable.

This work presents an ultra-wideband (UWB) low noise amplifier (LNA) with active shunt-feedback technique for wideband and flat gain by using standard 0.18 μm CMOS processes. Different from past resistive shunt-feedback technique, the capacitor supersedes by a transistor in active shunt-feedback technique. The active shunt-feedback provides input matching generating a 50 Ω real part with proper design and achieves flat gain from 2.5 GHz to 12 GHz. The UWB LNA achieved 11.4±0.2 dB gains, 4.5~5.2 dB noise figure (NF), 13.5 mW power consumption at frequency 3.1 GHz to 10.6 GHz, -15 dBm of 1-dB compression point (P1dB), and -3 dBm of input third intercept point (IIP3) at 6 GHz. The chip size including pads is only 0.6×0.5 mm².

Recently, we have introduced a numerical method for calculating local dispersion of arbitrary shaped optical waveguides, which is based on the Finite-Difference Time-domain and filter diagonalization technique. In this paper we present a study of photonic crystal waveguides at interfaces and double hetero-structure waveguides. We have studied the waveguide stretching effect, which is the change in lattice constant of photonic crystals along waveguiding direction. Hybrid modes at photonic crystal heterostructure interfaces are observed, which are the results of superposition of existing modes in adjacent waveguides. The dispersion at the interfaces of a double hetero-structure waveguide tends to the dispersion of outer waveguides. The effective area still holding the dispersion of the middle waveguide is shorter than the geometrical length of the middle waveguide. The results of this study present a clear picture of dispersion at interfaces and the transmission in photonic crystal hetero-structures.

This paper presents a multiband meandered loop antenna for smart phone applications. The proposed antenna which features a meandered folded-loop generates two resonance modes in the LTE/GSM bands. The current distributions of the excited resonance modes are analyzed to investigate the mode characteristic. By using a capacitively coupled feed on the backplane, the impedance bandwidth is broadened to cover LTE/WWAN bands. The simulation performed in this research used a high frequency structure simulator (HFSS) to optimally design the antenna, and a practical structure was constructed for the test. Details of the various antenna parameters are presented and discussed in this paper.

Several georeferenced measurements of electric field were done in a pilot area of Caracas, Venezuela, to verify that the magnitude of radio frequency electromagnetic fields is below the human exposure limits, recommended by the International Commission on Non-Ionizing Radiation Protection. The collected data were analyzed using geographical information systems, with the objective of using interpolation techniques to estimate the average electromagnetic field magnitude, to obtain a continuous dataset that could be represented over a map of the entire pilot area. This paper reviews the three methods of interpolation used: SPLINE, Inverse Distance Weighting (IDW) and KRIGING. A statistical assessment of the resultant continuous surfaces indicates that there is substantial difference between the estimating ability of the three interpolation methods and IDW performing better overall.

A scanning antenna at THz region is proposed and developed based on the quasi-optical techniques. It is composed of extended hemispherical lens/dielectric waveguide feed, inverse Cassegrain antenna, and transform lens. The extended hemispherical lens/dielectric waveguide feed is the key innovation of the scanning antenna. The inverse Cassegrain antenna is realized at THz region with special process and techniques, and the transform lens is used to match the input beam and the quasi-optical feed. The properties of the quasi-optical antenna are simulated with the FDTD method, and the experiments are carried out. The measured radiation pattern of the antenna is in agreement with the simulated result.

Novel compact microstrip quadruple-mode stub-loaded resonator and broadband bandpass filter (BPF) are proposed in this letter. As a starting part of designing a quadruple-mode broadband BPF, the initial novel triple-mode open impedance-stepped stub loaded resonator characteristic is investigated to choose its proper dimensions. Based on these pre-determined dimensions of the triple-mode resonator, two identical short-circuited stubs are loaded against the impedance-stepped open stubs in the resonator to generate a tuned resonant mode and a transmission zero in lower stopband which leads to a high rejection skirt. A compact broadband BPF with the quadruple-mode resonator is simulated, fabricated and measured. The measured results agree well with the EM simulations.

This paper presents a miniaturized branch-line coupler with suppression of wideband harmonics based on a unit of transmission-line section with triple-stub. This fundamental unit produces three transmission zeros and exhibits wide stopband response due to the triple stubs. It is used to replace a quarter-wavelength line in conventional branch-line coupler, leading to size reduction and wideband harmonics suppression. The closed-form equations are given for the coupler design. As an example, a branch-line coupler operating at 1.0 GHz is designed, fabricated and measured. Measurements agree well with simulations, and show that the proposed branch-line coupler occupies 56% size of a conventional one and achieves wideband harmonics suppression (better than 17 dB) from 1.8 GHz to 6.4 GHz. The 2nd, 3rd, 4th, 5th, and 6th harmonics are suppressed better than 34 dB, 19 dB, 30 dB, 17 dB, and 32 dB, respectively. With the theoretical analyses and practical results, it is shown that the proposed one has the advantages of simple structure, convenient analysis and wideband harmonics suppression.

A compact and simple interdigital capacitor inverted-F antenna (IFA) operated at its quarter-wavelength (λ/4) mode as the fundamental resonant mode for achieving multiband operation in the mobile phone is designed. The proposed antenna consists of a monopole antenna and an IFA. The proposed interdigital capacitor IFA has a simple structure of comprising two meandered radiating strips of length about λ/4 and is fed using an interdigital capacitor coupling feed. The two meandered radiating strips also generate two λ/4 resonance modes at about 900 MHz and 2100 MHz to cover the GSM850/900/1800/1900/DCS/PCS/UMTS bands and the 2.4 GHz WLAN (IEEE 802.11b) band operations. Further, the proposed antenna has a simple planar structure and occupies only a small area of 10×40 mm² on the system circuit board of the mobile phone. This proposed antenna with multiband, broadband matched impedance, stable radiation patterns, constant antenna gains, good radiation efficiency and compact size can be suitable for mobile phone applications.

A novel time-domain physical optics (TDPO) is proposed to determine the transient response of electromagnetic scattering of electrically large homogeneous dielectric targets modeled with triangular facets. Formula of the novel TDPO is derived, in which a time-domain convolution product between the incident plane wave and the time-domain physical-optics (PO) integral is included. The time-domain PO integral is evaluated with a closed-form expression based on a Radon transform interpretation, which makes the novel TDPO highly efficient in speed. The wideband rador cross section (RCS) is conveniently obtained from the transient response with a fast Fourier transform (FFT). Numerical results demonstrate the efficacy of the new method.