Shaped Beam Planar Antenna For Aerial Platforms

Enhancement in wireless and communication technology,has made antenna an essential part of airborne systems;where efficiency and performance of such systems,depends on radiation characteristics of an antenna.To achieve better efficiency and smooth signal coverage at wide range of angles,it is important to design an antenna with application specific radiation characteristics.At present,generally protruding antennas are used at aerial platforms because of their radiation pattern and good horizontal gain.Though such antennas illuminate large coverage area and provide omni-directional azimuth gain but lack the concept of beam-shaping for efficient utilization of signal strength at variant angles with reference to that of the distance to be achieved in the particular direction.Other than that,protruding antennas are considered aero-dynamically weak and have large RCS(radar-cross-section).For linearly-polarized beam-shaped antennas of the aerial platform,a vertically polarized beam-shaped planar antenna is designed and developed using hybrid of slot and loop configuration to achieve omni-directional pattern in azimuth plane,overlapped with a copper curl to provide beam-shaping in elevation plane.The proposed antenna provides different radiated power at variant angles as per beam-shaping requirements of aerial platforms.Simulated and measured results are provided and discussed during the thesis which show good horizontal gain(greater than 2.85 dBi),low azimuth gain ripple,high and stable gains(having peak gain of 6.4 ±.4 dBi)with smooth transitions with the change in elevation angles,to cover variant distances in different directions;over the entire operational frequency band(2.54 GHz to 2.69 GHz).Moreover,being planar antenna is more aero-dynamically and structurally ruggedized,surfacemount,and do not have extravagant RCS.For circularly-polarized beam-shaped antennas of the aerial platform,circular polarization(at angles against most-distant points)and direction based circular polarization diversity,is added in antenna configuration to increase communication range and provide benefits of diversity.Combination of vertically polarized slot-loop configuration and horizontally polarized stubs is proposed to achieve desired results.As target is to have suitable and efficient antenna for airborne systems,mounting capability(avoiding polarization and pattern distortion)over metallic vehicular body is a necessity.To make antenna surfacemount,split ring resonators are embedded in design formulation to control phase of reflected waves and avoid circular polarization distortion.Other than circular polarization and circular polarization diversity features,proposed antenna exhibit omnidirectional radiation characteristics,with good horizontal gain(greater than-3.6 dBi),and retain beam-shaped characteristics,along with having adequate peak polarization gain(2 to 4 dBic)through-out the operational bandwidth from2.82 GHz to 2.89 GHz.The target was to achieve circular polarization(axial ratio less than 3d B)at the elevation angles against most-distant points.Keeping that in view,proposed antenna exhibit circular polarized behavior over the entire functional frequency band.The results of proposed and designed formulations are validated by developing antenna prototypes,followed by detailed testing;before suggesting designed antenna formulations as worthy and prospective candidates for aerial platforms.