Optimization of a linearly polarized radial line slot array antenna design for direct broadcast satellite services

Abstract

Azimuthal components of beam squint design techniques for Linearly Polarized Radial Line Slot Array (LP-RLSA) antena was in the past chosen arbitrarily, which accounted for waste of quality design/simulation time and by extension the entire fabrication processes when poor design parameter is selected arbitrarily. This thesis introduces a more scientific method of identification and selection of azimuthal components (SØ) as a function of phi (Ø), thetaT (ƟT) and phiT (ØT) respectively via a numerical technique, which identifies optimal design parameters and formulates optimal equations. The thesis further studies the behaviour of dielectrics as it relates to the performance of the LP-RLSA antenas and has put in place suitable dielectric permittivity values required at Ku Band (12.25 - 12.75) GHz. Thus, a directivity value of more than 33.00 dBi was achieved at a frequency of 12.4 GHz with a reflection coeficient value less than -23.26 dB and a bandwidth of about 41% of 500MHz required. A radiation efficiency value of about 67% was achieved. Relationships between half power beam width (HPBW), slot widths (w) and antenna directivity (D) were studied, a new directivity relationship resulting from the study was formulated for the Ku Band (12.25 - 12.75) GHz. Research on the Ka Band LP-RLSA antenna design as an emerging technology for future satellite DBS service application at (21.4 - 22.0) GHz was done; CST MWS simulations were used, about 4 dBi higher in value of simulated directivity was obtained compared to the Ku Band design (12.25 - 12.75) GHz of same dish size (600 mm), with a bandwidth of about 41% of the 600 MHz required for the Ka Band DBS application at 21.699 GHz and 36.2 dBi realized. Good return loss performance of the Ka and Ku Bands design was achieved. Measured results for the Ku Band are in excellent agreement with the simulation results