LOW OBSERVABLE VIVALDI ANTENNA ARRAY FOR ELECTRONIC WARFARE APPLICATIONS

Vivaldi antennas have been widely used in phased array for aerospace platforms due to high gain, wide bandwidth and large scan angles.Further these antennae are end-fire radiating elements with low radar signatures.In this work, the main objective is to design a wideband Vivaldi antenna (2-18 GHz) with high gain and low radar cross-section (RCS) without disturbing other radiation parameters such as VSWR and gain.Firstly, a single Vivaldi antenna with proximity coupled microstrip feed has been designed to achieve the reflection coefficient below -10 dB for the frequency range of 2-18 GHz and the antenna gain greater than 5 dBi.The monostatic and bistatic RCS of the designed Vivaldi antenna was simulated for normal/oblique angles of incidence in vertical/horizontal polarizations.Further, the slots were introduced into the antenna structure for reducing the antenna RCS.It is shown that RCS reduction of 4-5 dB has been achieved without any degradation in the antenna performance.Next, a 4-element low RCS Vivaldi antenna array has been designed to achieve gain of 15 dBi.The inter-element spacing has been kept greater than half-wavelength to avoid mutual coupling.Such low observable Vivaldi array have Electronic Warfare applications.