A high gain wideband circularly polarized antenna with asymmetric metasurface

An asymmetric‐metasurface based wideband circularly polarized (CP) microstrip antenna using a coaxial probe is proposed for L‐band applications. The antenna involves a stacked asymmetric‐metasurface, a radiating rectangular‐patch and a coaxial feed. An asymmetric‐metasurface is designed using rectangular unit cells and smaller size unit cells along one of the diagonal lines. The asymmetric‐metasurface is placed above a radiating rectangular‐patch with support of foam layer to achieve a wideband CP radiation. The measured performance of the prototype antenna achieves an impedance bandwidth (?10 dB return loss bandwidth) of 15.7% (1.58‐1.85 GHz) with CP bandwidth (3‐dB axial ratio) of 13% (1.58‐1.80 GHz) and gain of ≥9 dBic.     

Process standardization for optimal virus recovery and removal of substrate DNA and bovine serum proteins in Vero cell-derived rabies vaccine

Purification of a rabies vaccine by a single zonal centrifugation run was replaced by two runs with optimal standardization of the sucrose density gradient. As a result, significant reductions in the levels of substrate DNA and bovine serum protein in the Vero cell-derived human rabies vaccine were achieved. Following many trials, for the first run, loading of the 3.2-l capacity K-3 rotor with 1800 ml of 60% sucrose solution and 1400 ml of vaccine PBS buffer solution gave a satisfactory linear gradient. However, after the first run, the substrate DNA and bovine serum contents exceeded the required levels. After protamine sulphate and Tween-80 treatment of the concentrated inactivated material, a second run using the same procedure as in the first run was tried. However, these purification procedures resulted in low virus recovery. To achieve optimal virus recovery, and removal of substrate DNA and bovine serum protein, the peak fractions from the first run as indicated by the haemagglutination, sucrose concentration, and optical density values were pooled and the sucrose concentration of the pooled fractions was increased to 60%. A second (flotation) run was then carried out. Using this method, the virus recovery rate was more than 95% that of the first run, and the levels of cellular DNA and bovine serum protein were well within the acceptable limits of less than 100 pg/dose and one part per million, respectively. The substrate DNA was quantified by both radioactive labeling and non-radioactive biotin labeling methods. For the quantification of calf serum protein, a counter-immunoelectrophoresis method was developed and effectively applied. A potency assay was performed using the National Institutes of Health (NIH) and well-standardized in vitro single radial immuno diffusion (SRD) methods. Finally, an immunogenicity study was conducted with human volunteers and the results were confirmed by a rapid fluorescent focus inhibition test (RFFIT).     

Base Station Placement for Dynamic Traffic Load Using Evolutionary Algorithms

In this paper, dynamic traffic load is considered to determine optimal location of base station (BS) using evolutionary optimization algorithms. The various parameters such as site coordinates (x, y), transmitting power, height and tilt are taken as design parameters for BS placement. Coverage maximization and cost minimization are considered as two conflicting objectives with inequality constraints such as handover, traffic demand and overlap. RGA and MNSGA-II algorithms are used to solve single objective and multiobjective BS placement problem respectively. A $2 \times 2\, \text{ km}^{2}$ synthetic test system is discretized as hexagonal cell structure for simulation purposes. Receiving field strength for all service testing points is calculated using simulations and path loss is calculated using Hata model. In dynamic traffic model, both vehicle and pedestrian movements in up and side directions are considered. Dynamic movement is achieved by randomly moving vehicles and pedestrians for a fixed speed in each sample time. The results show that the RGA is able to determine the optimal BS location after considering the dynamic traffic load and satisfying inequality constraints for both coverage maximization and cost objectives. MNSGA-II algorithm gives well distributed pareto-front for the multiobjective BS placement in single simulation run. The simulation results reveal that the proposed dynamic traffic model is suitable for the real world BS placement problem.     

A 105-nm ultrawide-band gain-flattened amplifier combining C- and L-band dual-core EDFAs in a parallel configuration

A novel structure for ultrawide-band gain-flattened amplifier by combining two pieces of C- and L-band dual-core erbium-doped fibers is reported. This novel amplifier has a flat gain of 15 dB over a wavelength range of 105 nm (1515-1620 nm). The gain variation for the C-band flat gain region (1515-1555 nm) is 1.3 dB, and for the L-band flat gain region (1562-1620 nm) is 1.5 dB. The noise figure varies from 4.5 to 4.8 dB over the whole bandwidth. The structure of the design is simple without the need of additional expensive components.     

Coplanar waveguide wideband bandpass filter and its application to ultra‐wideband pulse generation

A technique to design wideband coplanar waveguide bandpass filters is reported. The filter is realized by etching a slot on the ground plane around a gap on its central conductor and modifying the gap in the form of parallel lines. It is shown that the 3‐dB fractional bandwidth of the filter can be varied from 60 to 110% by tuning the size of the slot aperture and the length of the parallel lines. Equivalent circuit and design steps are presented. Implementation area of the filter having passband 3.2–10.5 GHz is 0.90 λ_g × 0.26 λ_g, λ_g being the guided wavelength at 6.85 GHz while 20‐dB stopband is at least up to 18 GHz. Insertion loss is less than 2 dB up to 9 GHz. Area of the filter having fractional bandwidth 60% at 3.85 GHz is 0.67 λ_g × 0.11 λ_g. Passband loss is within 1.5 and 20 dB stopband is at least up to 12 GHz. The proposed filter structure is very simple to integrate, and the ultra‐wideband filter is used to generate an ultra‐wideband pulse as defined by the US Federal Communication Commission. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Compact circularly polarized beam‐switching wireless power transfer system for ambient energy harvesting applications

In this work, we propose a circularly polarized (CP) beam‐switching wireless power transfer system for ambient energy harvesting applications operating at 2.4 GHz. Beam‐switching is achieved using a low profile, electrically small CP antenna array with four elements and a novel miniaturized 4× 4 butler matrix. The CP antenna is designed with an e‐shaped slot and four antennas. The CP antenna measures 0.32 λ₀× 0.32 λ₀× 0.006 λ₀ at 2.4 GHz. The antenna has a gain of 3 dBic and an axial ratio less than 3‐dB at 2.4 GHz. A linear antenna array consisting of four elements is designed with the CP antenna element with an inter‐element distance of 0.29 λ₀ . A 4× 4 butler matrix with miniaturized couplers and crossovers are used to feed the four antenna array elements. Based on the input port of excitation, the main beam of the antenna array is demonstrated to be switched to four directions: ?5°, 65°, ?55°, and 20°. A CP rectenna is used to demonstrate the wireless power transfer capability of the combination of the butler matrix and the CP‐antenna array. The rectenna consists of a Teo‐shaped CP antenna and a rectifier. The open circuit voltage at the output of the rectenna is found to peak value of 30 mV at ?3°, 61°, ?53°, and 17°. Thus a complete system for CP wireless power transfer including the power transmission system as well as the RF energy harvesting sensor is designed and experimentally verified.     

Nonlinear Distortion Due to Cross-Phase Modulation in Microwave Fiber-Optic Links With Optical Single-Sideband or Electrooptical Upconversion

A new analytical model is presented to study nonlinear distortion due to cross-phase modulation in dispersive and nonlinear wavelength-division-multiplexing microwave fiber-optic links. The model is not based on the pump-probe approach. Hence, it can be used to analyze a larger variety of links, including, in particular, electrooptical upconversion links. Our simulations and experiments show that the model predicts the nonlinear distortion due to cross-phase modulation quite accurately, even when the modulating microwave frequency is in tens of gigahertz and the fiber length is in tens of kilometers. Detailed analyses of the distortion due to cross-phase modulation for links with optical single-sideband modulation are presented. Measured results for optical single-sideband are shown to match our theoretical predictions very well. Our results show that the nonlinear distortion due to cross-phase modulation can be a limiting factor for optical launch power in wavelength-division-multiplexing microwave fiber-optic links; moreover, the maximum possible nonlinear distortion level for a higher frequency may be lower than that for a lower frequency. Also presented are some simple approximations for a quick estimate of the level of the nonlinear distortion     

Single-pole-four-throw switch using high-aspect-ratio lateral switches

A single-pole-four-throw (SP4T) switch using a high-aspect ratio lateral metal-contact micromachined switch is reported. This simplified SP4T micromachined switch is developed using deep reactive ion etching fabrication technology based on silicon-on-insulator wafer. The measurement results of the SP4T switch show an insertion loss of less than 1 dB and isolation of 30 dB from DC to 6 GHz.