In this paper, an ultra-wideband (UWB) bandpass filter (BPF) with a notch-band at 5.8 GHz is presented. The proposed filter is constructed with multiple-mode resonator (MMR) using novel dumbbell stubs and one-arm-folded interdigital coupled lines in the input and output sides. The MMR consists of three pairs of shunt dumbbell stubs and a high impedance microstrip line. By adjusting the dimensions of the dumbbell stubs, the resonant modes of MMR are allocated in the UWB band. The arm-folded interdigital coupled lines are used to obtain a notch-band at 5.8 GHz. Finally, the proposed UWB BPF is fabricated. The simulated and measured results are in good agreement with each other.

A Coplanar Wave guide (CPW) fed printed monopole antenna with reduced radiation hazard from a mobile handset is presented. The printed metal stripes in the back side of the monopole modify the far field pattern ideal for mobile handset. The antenna offers a bandwidth of 200 MHz when printed on a substrate of dielectric constant (εr) 4.4 and thickness 1.6 mm with an overall dimension of 42x31.7 mm². Experimental and simulation studies of the antenna radiation characteristics of the proposed antenna are presented and discussed. A 20 dB reduction of radiated power in one quadrant of the radiation pattern offers a reduction of radiation towards the users head.

In this paper, a new method for calculating transient electromagnetic responses of AC/DC power system with external electromagnetic pulse interference is proposed. An input-output model of three-phase bridge rectifier is presented for the transient calculation. In order to study the effect of the external electromagnetic pulse on the system, the field-to-line coupling model is introduced, and finite-difference time-domain method is adopted. Thus, the modeling method utilizes the analysis methods of the electric circuits and electromagnetic fields synthetically to deal with the coupled field-circuit problems. The model and algorithm are validated by comparing the calculation results with the experiment ones. Finally, the effects of some circuit parameters on transient responses are discussed. The method proposed in this paper lays the foundation for further researches on the transient electromagnetic performance of independent electrical power systems containing power electronics.

We derive integral representations suitable for studying the focusing of electromagnetic waves through a symmetrically hyperbolic focusing lens into uniaxial crystal in the presence of cylindrical and coma aberrations using Maslov's method. The uniaxial crystal used is the negative crystal LiNbO₃. Numerical computations are made to obtain the results for focused fields inside negative uniaxial crystal with several different orientations of the optical axis in the plane of incidence. The effects of aberrations inside uniaxial crystal and isotropic medium are also noted. The results are compared with those obtained by Kirchhoff-Huygens integral and Maslov's method which are in good agreement.

In this work, based on the principle of the electromagnetic reflection and transmission, we first present a theoretical analysis of a super-resolving lens with anti-reflection and phase control coatings (ARPC). This ARPC is capable of reducing the reflectivity of superlens surface and making phase difference approaching zero. The principle of ARPC is discussed in detail and the engineer condition for super-resolution imaging is obtained and the best range of the permittivity of ARPC coatings is obtained. The results demonstrate that the subwavelength resolution of our lens with ARPC has been enhanced. Such remarkable imaging capability using ARPC promises new potential for nanoscale imaging and lithography.

This paper describes the design and analysis of a Microstrip Reflectarray Antenna (MRA) with Minkowski shape radiating element at frequency of 11 GHz. This structure has been analyzed and compared with the traditional reflectarray element (square element patch). It is found that this antenna array has lower sidelobe level (SLL) characteristic which is down to -25 dB. This MRA has maximum realized gain of 29.6 dB with half-power beamwidth (HPBW) of 3.7°. The validation for the proposed MRA is done by comparing the simulated and measured E-plane radiation pattern. The difference margin between sweeping realized gain (simulation) and sweeping power received (measurement) had been compared within the frequency range of 10--12 GHz. A very good agreement is found from the comparison between simulation and measurement.

An efficient hybrid method is presented to obtain the current distribution of both non-uniformly linear and planar arrays By sampling the array factor of a desired radiation pattern, the proposed method provide Fourier coefficients and uses the Least Mean Square method (LMS) to solve the system of equations in order to obtain current distribution in associate with the desired radiation pattern. Obtained side lobe level is 3 dB lower than conventional methods such as LMS method or Legendre function method.

In this paper, we present a procedure to calculate the discrete modes propagated with Crank-Nicolson FDTD in metallic waveguides. This procedure enables the correct excitation of this kind of waveguides at any resolution. The problem is reduced to solving an eigenvalue equation, which is performed, both in a closed form, for the usual rectangular waveguide, and numerically in the most general case, validated here with a ridged rectangular waveguide.

A novel and simple antenna applicable to active RFID tags is designed. The designed antenna has been skillfully integrated with the active RFID tag circuit. The antenna consists of two parts. One part comprises stacked shorted patches and a ground plane. The other one is an active tag circuit mounted on the bottom of the antenna. By using the offset shorting posts technique, the proposed antenna can achieve an enhanced operating bandwidth with a small size. The measurement results reveal that the antenna has return loss less than -10 dB within the bandwidth of 42 MHz (from 914 MHz to 956 MHz), which totally covers the 5MHz bandwidth from 920MHz to 925 MHz (The band is also allowed for passive RFID) requirement for active RFID in China.

Antenna arrays with shaped power patterns have many applications in communications and radars. Many antenna array synthesis techniques for shaped patterns have been developed in the past years, and most of them deal only with uniformly spaced arrays. In this paper, a new method is proposed for the synthesis of nonuniform linear antenna arrays with shaped power patterns. The proposed synthesis method consists of three steps. First, we find a satisfactory power pattern for the required radiation characteristics by solving a constrained least-squares problem which is obtained with the help of non-redundant representation of squared magnitude of a linear array factor. Then, we factorize the polynomial associated with the power pattern by using polynomial rooting, and consequently obtain the corresponding field patterns. Finally, the forward-backward matrix pencil method is used to obtain a nonuniform linear array with optimized excitation magnitudes, phases and locations for a specific choice of field patterns. The synthesized array has a smaller number of elements than the one with uniformly spaced elements for the same pattern performance. Several synthesis experiments are conducted to validate the effectiveness and advantages of the proposed synthesis method.

Accurate approximations of the conductance and the conductance bandwidth of an electrically small antenna valid in resonant and antiresonant ranges were found. It is shown that the conductance bandwidth of an efficient antenna tuned on maximal power of radiation is inversely proportional to the magnitude of the frequency derivative of the input impedance |Z'(ω_cd)| of the antenna at frequency of maximal conductance. That is a generalization of the well known relationship according to which, the conductance bandwidth of an antenna tuned on resonance in resonant ranges is inversely proportional to the magnitude of the frequency derivative of the input reactance of the antenna |X'₀(ω₀)| at resonant frequency. Obtained approximate formulas display inverse proportionality of the conductance bandwidth to the approximate quality factor of the antenna throughout resonant and antiresonant ranges. A differential definition of the fractional conductance bandwidth was formulated, which is convenient for the case of closely spaced resonances of an antenna. As an example, numerical calculations for oblate spheroidal and spherical antennas in shells with negative permittivity in resonant and antiresonant ranges was used to confirm accuracy of the obtained approximations of the conductance and the conductance bandwidth of an electrically small antenna.

We report an analytical exciton emission model based on Green function for simulating the radiation characteristics of near-infrared Quantum Dot-light emitting devices (QD-LEDs). In this model the internally emitted light can be classified into the following modes: substrate, indium tin oxide (ITO)/organic waveguided, surface plasmonic modes, and external emitted mode. We investigate the influence of the thickness of different layers and the distance between the emitting center and the cathode metal on the emitted power distribution among these modes. In addition, we study the angular radiation profile for the externally emitted radiation and substrate waveguided mode in comparison with lambartian radiation profile. We show the change of the thickness of the different layers, and the positions of the emitting centers are critical to the optical performance of the device. The optimization of optical performance through device geometry increases the outcoupling efficiency more than five times.

This paper outlines typical issues in the design and fabrication of microstrip Wilkinson power dividers. As a practical solution, a modified Wilkinson divider configuration is proposed and designed for millimeter-wave antenna feeding networks. In this design, all microstrip branches and the resistive strip exhibit the same characteristic impedance. Probe measurements of Sparameters underline good matching, transmission and isolation characteristics of the proposed divider.

In order to reduce the monostatic signature of the junction between a radome and the metallic structure to which it is attached, a tapered resistive sheet can be used. In this paper, we describe an easy method to realize this tapering using geometric variations on a subwavelength scale, with a significant reduction of the number of processing steps as a result.

A novel, short-circuited, flat-plate dipole antenna for WLAN operation in the 2.4 GHz band is presented. The dipole antenna is narrow (5 mm in width) and structured to be of an L shape to fit in corners of possible wireless communications devices. The open ends of the two dipole arms are folded and face each other, so as to achieve a compact structure, and short-circuited via a short-circuiting strip, making it possible for the antenna to be cost-effectively fabricated by stamping one single metal plate only. The antenna when unbent into a flat, rectangular structure has dimensions 5 mm×47 mm and can be is easily fed by using a 50-Ω mini-coaxial cable. Details of a design prototype are described and discussed.

Considering microwaves as a viable alternative for the pasteurization of In-shell eggs, preliminary trials performed had confirmed that microwave at 2450 MHz can be successfully used to raise the temperature of in-shell eggs to the required pasteurization temperatures in a few minutes. Based on these trials a finite difference time domain (FDTD) model was developed using C language and MATLAB to simulate the E field and power distribution in lossy dielectric media like that of the egg components (egg white and yolk) taking into consideration the complex shape, dielectric properties and heterogeneous composition of the in-shell egg. This can be used to assist in the design and development of an industrial microwave in-shell eggs pasteurization unit.

In this paper the stability condition of the Runge-Kutta m-order multiresolution time-domain (RKm-MRTD) scheme has been studied. By analyzing the amplification factors, we derive the numerical dispersion relation of the RK-MRTD scheme. The numerical dispersive and dissipative errors are investigated. Finally, the theoretical predictions of the numerical errors are calculated through the numerical simulations.

Ultra wideband (UWB) Microwave imaging is one of the most promising emerging imaging technologies for breast cancer detection, and is based on the dielectric contrast between normal and cancerous tissues at microwave frequencies. UWB radar imaging involves illuminating the breast with a microwave pulse and reflected signals are used to determine the presence and location of significant dielectric scatterers, which may be representative of cancerous tissue within the breast. Beamformers are used to spatially focus the reflected signals and to compensate for path dependent attenuation and phase effects. While these beamforming algorithms have often been evaluated in isolation, variations in experimental conditions and metrics prompts the assessment of the beamformers on common anatomically and dielectrically representative breast models in order to effectively compare the performance of each. This paper seeks to investigate the following beamforming algorithms: Monostatic and Multistatic Delay-And-Sum (DAS), Delay-Multiply-And-Sum (DMAS) and Improved Delay-And-Sum (IDAS). The performance of each beamformer is evaluated across a range of appropriate metrics.

The concept of partially coherent four-petal Gaussian (PCFPG) beam is introduced and described in analytical forms. Based on the Huygens-Fresnel integral formula, average intensity and beam spreading in turbulent atmosphere are derived in analytical expressions. Effects of beam parameters and atmospheric structure constant on intensity distributions and effective beam sizes are investigated in detail, respectively. Results show that PCFPG beams carrying larger coherence lengths or higher beam orders would be less affected by turbulence. It is also indicated that, when the propagation distance increases, the PCFPG beam would convert into the Gauss-like profile sooner or later, but this degradation can be reduced by modulating beam parameters. Results in this paper may provide potential applications in free-space optical communications.

A novel wideband rectangular dielectric resonator antenna (DRA) is proposed in this paper. A hybrid structure with an isolated dielectric resonator (DR) and an equivalent air-dielectric DR is introduced by lifting the resonator from the ground plane. The hybrid structure is excited by a slot-fed mechanism to obtain a smooth transition between each resonant mode. The resonant modes of the isolated DR and the equivalent DR are merged together to form a wideband impedance bandwidth. It is found that the bandwidth of the proposed antenna can be greatly enhanced by using the hybrid DRA structure instead of the case mounted on the ground plane. A detailed parametric study is carried out to analyze the characteristics of the proposed antenna. Measured results show that the proposed DRA has a 10 dB impedance bandwidth of 61% from 2.4 GHz to 4.5 GHz and the radiation pattern is stable through the operating frequency.