An extraordinary transmission analogue for enhancing microwave antenna performance

The theory of diffraction limit proposed by H.A Bethe limits the total power transfer through a subwavelength hole. Researchers all over the world have gone through different techniques for boosting the transmission through subwavelength holes resulting in the Extraordinary Transmission (EOT) behavior. We examine computationally and experimentally the concept of EOT nature in the microwave range for enhancing radiation performance of a stacked dipole antenna working in the S band. It is shown that the front to back ratio of the antenna is considerably enhanced without affecting the impedance matching performance of the design. The computational analysis based on Finite Difference Time Domain (FDTD) method reveals that the excitation of Fabry-Perot resonant modes on the slots is responsible for performance enhancement

Investigation of SiC particle size variation on the tribological properties of Cu-6Sn-SiC composite

Copper have always been an important material and incorporation of elements into copper for property enhancement. Bronze is a relevant cuprous alloy which is important for many industrial and automotive applications like bearings and machineries. The present research is directed towards the fabrication and tribological analysis of regular bronze (Cu-6Sn) and metal matrix composites reinforced with varying particle sized SiC ceramic reinforcement (30, 35 and 40 \ub5m). The developed specimens were subjected to wear analysis according to ASTM standards, to identify the tribological properties utilizing a pin on disk tribometer. It was noted that the wear rates of developed MMC\u27s phenomenally decremented with an increase in size of SiC particle reinforcement. Also, the test parameters were influential in altering the wear rates to notable margins. The standard scanning electron microscopy techniques aided in identifying the influence of adhesive wear on the specimen surface

A metamaterial absorber based high gain directional dipole antenna

A novel idea for generating directional electromagnetic beam using a metamaterial absorber for enhancing radiation from a microwave antenna in the S-band is presented herewith. The metamaterial structure constitutes the well-known stacked dogbone doublet working in the absorption mode. The reflection property of the dogbone metamaterial absorber, for the non-propagating reactive near-field, is utilized for achieving highly enhanced and directional radiation characteristics. The metamaterial absorber converts the high-spatial reactive spectrum in the near-field into propagating low-spatial spectrum resulting in enhanced radiation efficiency and gain. The gain of a printed standard half-wave dipole is enhanced to 10 dBi from 2.3 dBi with highly directional radiation characteristics at resonance

Anomalous diffraction in hyperbolic materials

We demonstrate that light is subject to anomalous (i.e., negative) diffraction when propagating in the presence of hyperbolic dispersion. We show that light propagation in hyperbolic media resembles the dynamics of a quantum particle of negative mass moving in a two-dimensional potential. The negative effective mass implies time reversal if the medium is homogeneous. Such property paves the way to diffraction compensation, spatial analogue of dispersion compensating fibers in the temporal domain. At variance with materials exhibiting standard elliptic dispersion, in inhomogeneous hyperbolic materials light waves are pulled towards regions with a lower refractive index. In the presence of a Kerr-like optical response, bright (dark) solitons are supported by a negative (positive) nonlinearity.Comment: 10 pages, 10 figures; accepted for publication in Physical Review