Design and optimization of multi‐band Wilkinson power divider

In this paper, a general and easy procedure for designing the symmetrical Wilkinson power divider that achieves equal‐power split at N arbitrary frequencies is introduced. Each quarter‐wave branch in the conventional Wilkinson divider is replaced by N sections of transmission lines, and the isolation between the output ports is achieved by using N resistors. The design parameters are the characteristic impedances and lengths of the N transmission line sections, and the N isolation resistors. The even–odd modes of analysis are used to derive the design equations. Closed‐form expressions, which are suitable for CAD purposes, are derived for the dual‐band divider. For N ≥ 3, closed‐form expressions are not available, and therefore, the powerful particle swarm optimization method is used to obtain the design parameters. Examples of the dual‐, triple‐, and quad‐band dividers are presented to validate the proposed design procedure, and the results are compared, wherever possible, with published results using other methods. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Finite difference time domain analysis of cylindrical coplanar waveguide circuits

There is a growing interest in using cylindrical transmission line structures in microwave applications. In this paper, the finite difference time domain (FDTD) method is used to characterize several three-dimensional cylindrical coplanar waveguide (CCPW) geometries. Specifically, a CCPW series stub and a three-section CCPW filter are studied both theoretically and experimentally. Moreover, CCPW gap is characterized and the FDTD results are compared to those obtained using conformal mapping techniques. Effective absorbing boundary conditions are employed to truncate the FDTD mesh at the end walls and the outer radial boundary.     

Effect of edible coatings on fruit maturity and fungal growth on Berhi dates

Berhi date palm fruits were harvested at the khalal stage, coated with different edible materials: pea starch (PS), zein protein (ZP), pea starch + carnauba wax (PS + CW) and zein protein + carnauba wax (ZP + CW) and stored at 3 or 25 °C for 21 days. Different fruit maturity indicators (colour, firmness, total soluble solids, moisture and tannins) and fungal numbers were monitored during storage. PS and ZP coatings at 3 °C were the most effective in retarding fruit maturation by extending the khalal stage from 7 to >14 days. They were less effective at 25 °C, where the khalal stage was extended only ≤7 days. PS + CW and ZP + CW coatings prevented sample moisture loss, but they accelerated degradation of simple sugars at 25 °C, and this indicated a shift to anaerobic fruit respiration. The PS + CW and ZP + CW coatings, particularly at 3 °C, were the most effective in preventing fungal growth, whereas the PS coating promoted fungal growth.     

50-Gb/s SiGe BiCMOS 4:1 multiplexer and 1:4 demultiplexer for serial communication systems

4:1 multiplexer and 1:4 demultiplexer ICs targeting SONET OC-768 applications are reported. The ICs have been implemented using a 120-GHz-f/sub T/ 0.18-/spl mu/m SiGe BiCMOS process. Both ICs have been packaged to enable bit error rate testing by connecting their serial interfaces. Error-free operation has been achieved for both circuits at data rates beyond 50 Gb/s. At a -3.6-V supply voltage, the multiplexer and demultiplexer dissipate 410 and 430 mA, respectively. Switching behavior of the 4:1 multiplexer has also been checked up to 70 Gb/s.     

Design of optimum gain pyramidal horn with improved formulas using particle swarm optimization

In this article, a new method to design an optimum gain horn antenna is presented. This method is based on improving existing design equations along with the use of particle swarm optimization technique. The obtained results are more accurate than those available in the literature since no path length error approximation is involved. Improved horn dimensions, for different 15 designs, are obtained which give the desired gain almost exactly. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Synthesis of interdigital capacitors based on particle swarm optimization and artificial neural networks

This article reports on the use of the particle swarm optimization (PSO) algorithm in the synthesis of the planar interdigital capacitor (IDC). The PSO algorithm is used to optimize the geometry parameters of the IDC in order to obtain a certain capacitance value. The capacitance value of the IDC is evaluated using an artificial neural network (ANN) model with the geometry parameters of the IDC as its inputs. Several design examples are presented that illustrate the use of the PSO algorithm, and the design goal in each example is easily achieved. Full‐wave electromagnetic simulations are also performed for some of the studied IDC structures implemented using coplanar waveguide (CPW) technology. The simulation results are in good agreement with those obtained using the ANN/PSO algorithm. © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Neuroprotective Effect of Gold Nanoparticles and Alpha-Lipoic Acid Mixture against Radiation-Induced Brain Damage in Rats

The current study aims to evaluate the possible neuroprotective impact of gold nanoparticles (AuNPs) and an alpha-lipoic acid (ALA) mixture against brain damage in irradiated rats. AuNPs were synthesized and characterized using different techniques. Then, a preliminary investigation was carried out to determine the neuroprotective dose of AuNPs, where three single doses (500, 1000, and 1500 µg/kg) were orally administrated to male Wistar rats, one hour before being exposed to a single dose of 7Gy gamma radiation. One day following irradiation, the estimation of oxidative stress biomarkers (malondialdehyde, MDA; glutathione peroxidase, GPX), DNA fragmentation, and histopathological alterations were performed in brain cortical and hippocampal tissues in both normal and irradiated rats. The chosen neuroprotective dose of AuNPs (1000 µg/kg) was processed with ALA (100 mg/kg) to prepare the AuNPs-ALA mixture. The acute neuroprotective effect of AuNPs-ALA in irradiated rats was determined against valproic acid as a neuroprotective centrally acting reference drug. All drugs were orally administered one hour before the 7Gy-gamma irradiation. One day following irradiation, animals were sacrificed and exposed to examinations such as those of the preliminary experiment. Administration of AuNPs, ALA, and AuNPs-ALA mixture before irradiation significantly attenuated the radiation-induced oxidative stress through amelioration of MDA content and GPX activity along with alleviating DNA fragmentation and histopathological changes in both cortical and hippocampal tissues. Notably, the AuNPs-ALA mixture showed superior effect compared to that of AuNPs or ALA alone, as it mitigated oxidative stress, DNA damage, and histopathological injury collectively. Administration of AuNPs-ALA resulted in normalized MDA content, increased GPX activity, restored DNA content in the cortex and hippocampus besides only mild histopathological changes. The present data suggest that the AuNPs-ALA mixture may be considered a potential candidate for alleviating radiation-associated brain toxicity.     

A Two-dimensional Full-wave Finite-difference Frequency-domain Analysis of Ferrite Loaded Structures

A two-dimensional (2-D) full-wave finite-difference frequency-domain (FDFD) method is presented for analyzing the dispersion characteristics of transversely magnetized ferrite loaded structures. Results for a number of different ferrite loaded structures are presented. The accuracy of the FDFD formulation is verified by comparing the numerical results with analytical results and those obtained using the FDTD method, and very good agreement is obtained.     

Quasi-static analysis of asymmetric cylindrical coplanar waveguides with finite-extent ground

Quasi-static characteristics of asymmetric cylindrical coplanar waveguides (CCPWs) with finite-extent ground are analysed using the conformal mapping technique. Closed-form expressions for the effective permittivity and characteristic impedance of inside and outside asymmetric CCPWs with finite ground are derived. Using these expressions, the effect of various parameters on the characteristics of CCPWs is studied.     

40-Gb/s circuits built from a 120-GHz f/sub T/ SiGe technology

Product designs for 40-Gb/s applications fabricated from SiGe BiCMOS technologies are now becoming available. In this paper we first briefly discuss heterojunction bipolar transistor (HBT) device operation at high speed, demonstrating that perceived concerns regarding lower BV/sub CEO/ and higher current densities required to operate silicon HBTs at such high speeds do not in actuality limit design or performance. The high-speed portions of the 40-Gb/s system are then addressed individually. We demonstrate the digital capability through a 4: 1 multiplexer and a 1 : 4 demultiplexer running over 50 Gb/s error free at a -3.3-V power supply. We also demonstrate a range of analog elements, including a lumped limiting amplifier which operates with a 35-GHz bandwidth, a transimpedance amplifier with 220-/spl Omega/ gain and 49.1-GHz bandwidth, a 21.5-GHz voltage-controlled oscillator with over -100-dBc/Hz phase noise at 1-MHz offset, and a modulator driver which runs a voltage swing twice the BV/sub CEO/ of the high-speed SiGe HBT. These parts demonstrate substantial results toward product offerings, on each of the critical high-speed elements of the 40-Gb/s system.