Current Issue : October - December Volume : 2014 Issue Number : 4 Articles : 4 Articles
A quasi-Yagi antenna is developed to operate at 2.4GHz (ISMband) presenting a low profile and off-axis radiation when packaged\nover ametal ground plane.Theoff-axis radiation is realized by incorporating a Jerusalem cross frequency selective surface (JC-FSS)\nas the ground plane for the antenna. A JC-FSS is preferred because of its frequency stability in the operating band for a large angular\nspectrum (?70?) of TE- and TM-polarized incident waves. In this research, the substrate of the antenna flush-mounted on top of\nthe FSS is added to the JC-FSS model and allows for a smaller cell grid. The prepared quasi-Yagi antenna over the JC-FSS offered\n260MHz of functional bandwidth and 54? of beam tilt towards the end-fire direction. To the best of the authors� knowledge this\nis the first instance that these two structures are combined for off-axis radiation. Additionally, to support the preferred use of the\nJC-FSS, the quasi-Yagi is backed by a square patch (SP) FSS for comparison purposes....
An alternative radiation stabilization method has been presented for patch antenna. With this method, side radiation could be\nsuppressed when a conductor ring and a circular slot both with the width of a quarter-wavelength are placed on the same layer\nand around patch antenna. An experimental structure has been simulated and the distance ???? from antenna part to conductor ring\nis optimized using parametric function of HFSS software.Measured results given in this paper obviously indicate that not only the\nside radiation fromthe boundary of substrate could be suppressed effectively, but also the antenna directivity could be adjusted and\nenhanced after this method has been carried out. Both simulation and measurement indicate that when the distance ???? is set to one\nguided wavelength (????????), side radiation could be suppressed the most effectively and the return loss of patch antenna is only slightly\naffected....
Phenol contaminated petroleum refinery wastewater presents a great threat on water resources safety. This study investigates the\neffect of microwave irradiation on removal of different concentrations of phenol in an attempt for petroleum refinery wastewater\ntreatment.Theobtained results showthat theMWoutput power and irradiation time have a significant positive effect on the removal\nefficiency of phenol. The kinetic reaction is significantly affected by initial MW output power and initial phenol concentrations.\nResponse surface methodology (RSM) was employed to optimize and study the interaction effects of process parameters: MW\noutput power, irradiation time, salinity, pH, andH2O2 concentration using central composite design (CCD). Fromthe CCD design\nmatrix, a quadratic model was considered as an ultimate model (R2 = 0.75) and its adequacy was justified through analysis of\nvariance (ANOVA). The overall reaction rates were significantly enhanced in the combined MW/H2O2 system as proved by RSM.\nTheoptimumvalues for the design parameters of theMW/H2O2 processwere evaluated giving predicted phenol removal percentage\nof 72.90% through RSM by differential approximation and were confirmed by experimental phenol removal of 75.70% in a batch\nexperiment at optimum conditions of 439W MW power, irradiation time of 24.22 min, salinity of 574mg/L, pH 5.10, and initial\nH2O2 concentration of 10% (v/v)....
A new concept of an ultrawide bandwidth 180?-hybrid-coupler is presented. The ultrawideband design approach is based on the\nexcitation of a coplanar waveguide (CPW) mode and a coupled slot line (CSL) mode in the same double slotted planar waveguide.\nThecoupler is suitable for realization in planar printed circuit board technology. For verification of the new concept a prototype was\ndesigned for the frequency range from3GHz to 11GHz, built, andmeasured.Themeasurement results presented in this paper show\na good agreement between simulation and measurement and demonstrate the very broadband performance of the new device. The\ndemonstrated coupler with a size of 40mmÃ?â?? 55mm exhibits a fractional bandwidth of 114% centered at 7GHz with a maximum\namplitude imbalance of 0.8 dB and a maximum phase imbalance of 5?....
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