Wide band blade antenna design for airplatforms

Communication and electronic warfare application in avionics requires broadband antennas which provides omnidirectional radiation in VHF, UHF and L bands. Planar dipole/monopole, discone, spiral, annular slot and blade antennas are frequently used antennas in air platforms. These antennas may differ in some antenna parameters such as size, aerodynamic structure, radiation patterns, and gain. Blade antennas are preferred to be used in air platforms due to their omnidirectional radiation pattern, comparatively large bandwidth and compact size. In fact, blade antennas are a sort of monopole antennas. Monopole antennas requires a ground plane as a necessity of their structure. Blade antennas used in avionics utilizes the outer surface of the air platform as the ground plane. Blade antennas includes notches on each side of antenna, in front and at the rear of the antenna. The objective of implementing notches on the blade antenna is to shorten the height of the antenna, which in turn results in a reduction of the Q, Quality factor, to achieve a broadband antenna. In this thesis, a broadband blade antenna suitable to be used in air platforms has been designed. Impedance matching is achieved in the frequency range of 0.82 GHz-2.04 GHz. A gain of 6.48 dB is achieved within this frequency band. The radiation pattern is shown to be omnidirectional. The designed blade antenna height is 95 mm and the dimension of ground plane used is 500 x 500 mm2. Additionally, a flat antenna with no notches on the antenna has been designed by taking the same frequency band, the same dimensions and the same ground plane. It has been shown that the blade antenna with notches has shown superiority over the flat antenna. The designed blade antenna with notches and the flat antenna with the same parameters used in the design were fabricated. The measurement of S11 for the fabricated antennas provided similar values to the simulation results of the designed antennas. Thus, the antenna design in this thesis has been tested and proven through antennas' fabrication.