In this paper, a large signal equivalent circuit empirical model based on Anglov model for ceramic packed high power AlGaN/GaN HEMT has been proposed. A temperature-dependent drain current model, including self-heating effect, has been presented, and good agreement is achieved between measurement results and the calculated results at different temperature. The nonlinear capacitance models are modeled by the directly measured microwave scattering (S) parameters and multi-bias small signal equivalent model (SSECM) of packed device. A power amplifier based on large size AlGaN/GaN HEMT with a total gate periphery of 36 mm has been designed by using the proposed model for validation purpose, and the simulated results fit the measurement results well at different temperature.

This paper studies the surface modes at the interface of finite size Electromagnetic Band Gap (EBG) woodpile structures. The impact of different types of woodpile terminations on the properties of these surface modes is analyzed. For all the studied terminations there exist surface modes which must be taken into account when designing components based on this EBG structure.

A simple finite difference time domain (FDTD) scheme is proposed for modeling three-dimensional (3D) nondispersive chiral media. Based on the recently reported new BI-FDTD mesh method and rearranged curl equations, this scheme implements a simple leapfrog algorithm. By adding the mirror layer, the perfect electric conductor (PEC) condition is implemented in the BI-FDTD mesh method of 3D problem. Results of this scheme are presented for the scattering coefficients of discontinuity in waveguides, which are partially filled with chiral or achiral media. The validation is performed by comparing the results with those obtained from the literature and software simulation.

In this paper, a novel microwave bandpass filter structure is proposed. By introducing a metallic via hole, the filter structure operates as one λ/2 and two λ/4 uniform impedance resonators and consequently form a triplet coupling scheme. The equivalent circuit model is analyzed in detail, which shows that there is a transmission zero in the low stopband. Based on that concept, three microstrip filters are designed, fabricated and measured, respectively. The first filter has no source/load coupling and only one transmission zero is created. By introducing source/load coupling, the second filter can create three transmission zeros. The third filter can create a controllable transmission zero in upper stopband. The simulated and measured results agree very well.

Perfect electromagnetic conductor (PEMC) is a novel concept in electromagnetic fields of interesting properties and many potential applications. This paper introduces a new technique to design an artificial surface that has equivalent PEMC properties. The proposed PEMC boundary is based on a periodic structure composed of two conducting patches on a grounded dielectric slab. One of them is embedded inside the substrate and the other lies on the surface of the substrate. A conducting via is used to connect the two patches. In the resulting PEMC boundary, the polarization of the reflected wave is controlled by the tilting angle between the two patches.

In this paper a new method based on the complex images technique has been presented to efficiently compute the Green's functions required in a Mixed Potential Integral Equation (MPIE) analysis of a periodic structure located in a layered medium. This method leads to a closed-form representation for these slowly convergent series valid for sub-wavelength as well as super-wavelength cell sizes for all source point to field point distances. Comparison between the results obtained by the proposed method with ones obtained from other numerical approaches verifies its accuracy. Fast convergence, simple final form and versatility of the proposed method are its main advantages which make it suitable for the analysis of the periodic structures using the integral equation techniques.

We report on free space transmission experiments carried out on stacked split ring resonator (SRRs) arrays operating at microwave frequencies. We start from the case of a single frequency selective surface which exhibits a rejection at the SRR resonance frequency. By stacking SRR arrays in the propagation direction, we then show experimentally the possibility to induce a transmission band just below this resonance frequency. Full wave analysis shows the role played by the longitudinal and transverse coupling effects in the electromagnetic properties of such bulk metamaterials, with the appearance of a transmission band resulting from an artificial magnetic activity.

This paper presents a printed dipole with left-handed loading and electrically small dimensions. Uniform currents are obtained at 750 MHz, proving zero order (i.e. n=0) mode operation. Comparisons are made with other left- and right-handed antennas. Good agreement is achieved between simulation and measurement. The antenna has various applications in RFID systems and wireless environments.

A novel wafer-dipole printed antenna fed by balanced micro-strip line is proposed, and the adoption of the balanced micro-strip line can effectively solve the feeding problem of the UWB dipole antenna. The wafer-dipole and a branch of the balanced microstripline are printed on one side of FR-4 substrate (1mm thickness), and the later is connected to a wafer directly, while the other branch is printed on the back side of the substrate and connected the other wafer with a via-hole. The measured results show that the antenna impedance bandwidth is from 3.0 GHz to 15.0 GHz with VSWR < 2, and the ratio bandwidth is about 5:1. Moreover, the antenna size is just 40 mm×20 mm with simple structure, which is well suited for short-distance UWB communications.

This paper presents the design and test results of a 20-GHz transmitter front-end implemented in the TSMC 0.13-μm CMOS process. The chip consists of a voltage-controlled oscillator (VCO), an RC phase splitter, and two differential switches. To realize the K-band transmitter function, the two different switches are designed to serve the purpose of frequency doubler and phase modulator, respectively. These two features are verified in the implemented chip and, as a result, the chip can serve as a transmitter front-end. The measured total current consumption of the chip core circuit is 26 mA under a DC supply voltage of 1.2 V. The chip size is 1.03×0.93 mm².

In this work we propose a new class of optical pressure sensors suitable for robot tactile sensing. The sensors are based on a tapered optical fiber, where optical signals travel, embedded into a PDMS-gold nanocomposite material. By applying different pressure forces onto the PDMS-based nanocomposite we measure in real time the change of the optical transmittivity due to the coupling between the gold nanocomposite material and the tapered fiber region. The intensity reduction of the transmitted light intensity is correlated with the pressure force magnitude.

Compared with MPI, OpenMP provides us an easy way to parallelize the multilevel fast multipole algorithm (MLFMA) on shared-memory systems. However, the implementation of OpenMP parallelization has many pitfalls because different parts of the MLFMA have distinct numerical characteristics due to its complicated algorithm structure. These pitfalls often cause very low efficiency, especially when many threads are employed. Through an in-depth investigation on these pitfalls with analysis and numerical experiments, we propose an efficient OpenMP parallel MLFMA. Three strategies are proposed in the parallelization, including: 1) the choice of OpenMP schedule manners; 2) loop reorganization for far-field interaction in the MLFMA; 3) determination of a transition level. Numerical experiments on large scale targets show the proposed OpenMP parallel scheme can perform as efficiently as the MPI counterpart, and much more efficiently than the straightforward OpenMP parallel one.

This paper is devoted on the characterization method of RF/digital PCB interconnections for the prediction of the high-speed signal transient responses. The introduced method is based on the use of the interconnection line RLCG-model. Theoretical formulae enabling the extraction of the electrical per-unit length parameters R, L, C and G in function of the interconnection line physical characteristics (width, length, metal conductivity, dielectric permittivity ...) are established. Then, by considering the second order approximation of the interconnection RLCG-model transfer matrix, the calculation process of the transient responses from the interconnection system transfer function is originally established. To demonstrate the relevance of the proposed model, microwave-digital interconnection structure comprised of millimetre microstrip line driven and loaded by logic gates which are respectively modelled by their input and output impedances was considered. Then, comparisons between the SPICE-computation results and those obtained from the proposed analytical model implemented in Matlab were made. As results, by considering a periodical square microwave-digital excitation signal with 2 Gbits/s rate, transient responses which are very well-correlated to the SPICE-results and showing the degradation of the tested signal fidelity are observed. The numerical computations confirm that the proposed modelling method enables also to evaluate accurately the transient signal parameters as the rise-/fall-times and the 50% propagation delay in very less computation time. For this reason, this analytical-numerical modelling method is potentially interesting for the analysis of the signal integrity which propagates in the high-speed complex interconnection systems as the clock tree distribution networks. In the continuation of this work, we would like to apply the proposed modelling process for the enhancement of signal quality degraded by the RF/digital circuit board interconnection where the signal delays and losses became considerably critical.

A highly miniaturized simplified composite right/left handed (SCRLH) mushroom zeroth-order resonator (MZOR) is proposed for bandpass filter (BPF) design. By introducing the U-slot etched around the metallic via (UEAV), more flexible selection of the shunt inductance value can be achieved compared with the original one. As the length of UEAV increased, zeroth-order resonant frequency of the MZOR decreased, even 88% size reduction can be achieved. Finally, a bandpass filter based on the proposed MZOR is designed, fabricated and measured. The simulated and measured results are presented and good agreement is obtained.

A novel bandwidth enhancement design of planar F-shaped dipole antenna for RFID tag is proposed. With the use of two parasitic strips inset along the closed loop of the input IC chip in this proposed tag antenna, a new resonant mode close to 900 MHz band is excited to enhance the operating bandwidth. The obtained impedance bandwidth across the operating band can reach about 104 MHz for UHF band. With omni-directional reading pattern, the measured reading distance is about 2.8 m as the tag antenna mounted on the glass object.

The paper describes the modelling of the average rainfall rate distribution measured at different locations in South Africa. There are three major aspects this paper addresses: to develop a rainfall rate model based on the maximum likelihood method (ML); to develop contour maps based on rainfall rate at 0.01% percentage of exceedence; and re-classification of the ITU-R and Crane rain zones for the Southern Africa region. The work presented is based on five-minute rainfall data converted to one-minute equivalent using a newly proposed hybrid method. The results are mapped and compared with conventional models such as the ITU-R model, Rice-Holmberg, Moupfouma and Crane models. The proposed rainfall rate models are compared and evaluated using root mean square and chi-square (χ²) statistics. Then re-classification of the rain zone using ITU-R and Crane designations is suggested for easy integration with existing radio planning tools. The rainfall rate contour maps at 0.01% percentage of exceedence are then developed for South Africa and its surrounding islands.

We present an optical model based on Green function to investigate the effect of using Single Wall Carbon Nanotube (SWCNT) as anode for infrared light emitting devices (IR QD-LEDs). To the best of our knowledge there is no report in using SWCNT as anode in IR QD-LEDs. We have studied the emitted power distribution among the different optical modes (air, substrate, anode/organics, and surface plasmon modes (SP)), angular intensity distribution, and the emission spectral characteristics. We have found that the light outcoupling efficiency of IR QD-LEDs based on SWCNT as anode was increased nearly by a factor of 4 relative to that one based on indium-tin oxide (ITO). We also investigated the effect of using different cathode materials on the optical characteristics of IR QD-LEDs.

To investigate the effects of pulsed electromagnetic field (PEMF) with high electric field intensity on bone formation in murine osteoblast-like MC3T3-E1 cells, proliferation, alkaline phosphotase (ALP) activity, mineralized nodule formation, Collagen Type I (COL-I) and core-binding factor (Cbf)a1 mRNA expression, and bone morphogenetic protein (BMP)2/4 and mothers against decapentaplegic (Smad)1/5/8 protein expression were examined in cultured MC3T3-E1 cells after exposure to PEMF at the field intensities of 0kV/m, 50kV/m or 400kV/m for 400 consecutive pulses daily for 7 consecutive days. After 50 kV/m of PEMF exposure, none of the above parameters of MC3T3-E1 cells changed significantly when compared to the control groups. However, the proliferation, ALP activity and mineralized nodule formation of MC3T3-E1 cells in 400 kV/m PEMF exposure groups decreased significantly although COL-I and Cbfa1 mRNA expression and BMP2/4 and Smad1/5/8 protein expression did not change. The PEMF we used at high electric field intensity suppressed proliferation, differentiation and mineralization of MC3T3-E1 cells in culture and appeared to be harmful for bone formation.

In this paper, a reduced size dual-frequency Wilkinson power divider (WPD) is presented. The miniaturization is accomplished by using two sections of non-uniform transmission line transformers in place of the two uniform sections in the conventional dual-frequency WPD. Two isolation resistors are also used to achieve good isolation between the output ports. Optimization is carried out based on simple uniform transmission line theory. For verification purposes, a dual-frequency WPD operating at 0.5 GHz and 1 GHz is designed, analyzed and fabricated.

In this paper, a parametric electromagnetic radiated emission model has been explored. Several mathematical improvements with respect to its extraction and computational performance have been deployed. The model, represented with an array of radiating electric dipoles, predicts the electromagnetic emission of components and systems. Core-level changes have been made in order to extract the model parameters: the dipole positions, their orientations and currents, and the effective relative permittivity from near-field measurements. Thresholding and windowing techniques are used to detect and optimize dipole positions, directly from the field data. A fast and memory efficient two-level optimization algorithm based on the Levenberg-Marquardt non-linear least squares technique is implemented for parametric extraction. All the constraints of the previous model have been overcome and the system is validated for mono-substrate and multi-substrate devices from measurements and/or simulations, with promising results. A tremendous improvement in modeling capability and performance has been obtained when compared with that of its erstwhile counterpart.