Central-fed hemispherical helical antenna
The characteristics of a hemispherical helical antenna with central-fed are investigated by experiment. Results for a 3-turn hemispherical helix indicate that circular polarization can be obtained over a wide angular range with relatively high gain of about 8 dB. The frequency bandwidth for a 3-dB axial ratio criterion is /spl sim/11%, with a nearly resistive input impedance of 163 /spl Omega/.
Comparison between MATLAB and CST Simulated Results of Helical Antenna Implementation for Ku-band Application
This study implements the design of an axial mode helical antenna for Ku-band applications. It employs the design curves approach using MATLAB simulations for gain and bandwidth computations in relation to axial length and pitch angles. Same design parameters were used on CST microwave studio (CST 2010) to provide a basis for comparison between results obtained from MATLAB simulations with those from CST 2010. Calculated values of the normalized free space axial length gave a gain of 21.03 dBi at 14 λ axial length and a bandwidth of about 13% from MATLAB computations. However, same design parameters implemented on CST 2010 shows conflicting agreements with results obtained from MATLAB simulations, thus the need to itemize the limitations of this antenna design for Ku band satellite applications as a tool for further studies.
Anomalous Annealing Behavior of Arsenic Implanted Silicon as a Function of Dose and Energy
Anomalous annealing behavior of damage in As implanted Si has been investigated by channeling effect measurements. Room temperature As implants with doses from 1014 to 2 × 1016cm-2 at energies ranging from 50 to 250 keV into Si were annealed over the range of 600°C to 1100°C. Anneal temperatures ≥ 950°C reduce the disorder for ion doses of 0.5 to 1 × 1016 cm-2 at energies between 50 and 250 keV. Anomalously high residual disorder was found for the intermediate doses of 2 × 1014 to 2 × 10/cm2 implanted above 100 keV. For this intermediate dose, annealing of implants performed at liquid nitrogen temperatures did not show significant reduction in this damage. However implants at 200° to 300°C indicate a lower amount of damage compared to the room temperature implants.