İki frekans bandinda farklı polarizasyon tiplerinde çalısan vivaldi anten tasarımı

This thesis presents a novel dual-polarized antenna design based on two orthogonally place Vivaldi antenna elements and are driven by a specially designed feeding network that splits incoming signal into two wherein one of them is linearly polarized between 4 and 6 GHz and the other one is circularly polarized from 14.5 to 15.5 GHz. Splitting of input signal into the two frequency bands, a diplexer is designed. A wilkinson power divider and a transmission-line phase shifter are employed to realize $90^{o}$ phase difference to achieve circular polarization at the upper frequency band. The feed network is integrated with the Vivaldi elements to ensure a compact form factor critical for reflector applications. In order to avoid crossing of two microstrip-to-slotline transition of the two Vivaldi elements, a small shift between them is introduced. This antenna is intended to be used as a feed antenna for reflector systems employed in radio link systems of drones. Combination of these distinct frequency bands with different polarization requirements allows use of single ground control antenna instead of two independent antennas thereby reducing cost and space requirements. For demonstration purpose, a prototype is fabricated. The antenna achieves better than -15 dB input reflection coefficients over most of the operating bands and axial ratio is less than 2 dB for the upper frequency range. The antenna exhibits gain between 7.2 to 9.5 dBi from 4 to 16 GHz. Meanwhile, stable radiation patterns are achieved with the cross polarization lower than -25 dB across the operating bands at boresight direction.