Circularly polarized broadband antenna with circular slot on circular ground plane

A novel circularly polarized antenna with a circular radiating aperture and circular ground plane for broadband characteristics is presented in this paper. The vertical and horizontal components of the L-shaped probe are separated and placed at the front and back sides of the substrate. The antenna is excited by a microstrip line which is connected to the vertical component of the L-shaped probe and electromagnetically couples the signal to the horizontal component of the L-shaped probe. The concept of placing an appropriate stub in the slot, by observing the electric field vector behaviour in the slot, is proposed to enhance the axial ratio (AR) bandwidth by around 15%. The fabricated antenna shows wideband impedance and circular polarization characteristics of 48% along with a maximum gain of 6 dBic. The measured and simulated antenna characteristics are in good agreement

ATOM PROBE FIM STUDY OF AN AMORPHOUS Pd-Si ALLOY

The amorphous structure of Pd84Si16 alloy wire obtained by inrotating-liquid spinning method from the liquid state, has been studied, in an atomic scale, by atom-probe field-ion microscopy. In the as-solidified specimen of Pd84Si16 alloy, whose electron diffraction pattern shows single halo ring, compositional fluctuation is found to exist in the range of 8 to 24 at% Si. The fluctuation is of the period of a few tenth nanometer, and it does not have long-range periodicity. We have discussed these experimental results with microcompositional fluctuation in terms of both amorphous structure itself and artifact effect with field evaporation