Dielectric Free Wide Scan UWB Low Cross-Pol Metallic Vivaldi Antenna for Active Phased Array Radars

Abstract

Tapered slot antennas (TSA) or Vivaldi antennas (VA) arrays studied extensively for many decades have proved to be a potential candidate for wide band (WB) and wide scan (WS) phased array antennas. Earlier analyses have shown that their WB performance suffers from few impedance anomalies due to the coupling associated with surface waves in dielectric substrates and the inter-element gaps in an array. Many researchers have dealt with these problems, proposed metallic TSAs or VAs with elements joined along one of the principal planes (usually E-plane) demonstrating wideband and wide scan capabilities. The author complements the existing research and presents an ultra- WB (UWB), wide beamwidth (HPBW), low cross-polarized (x-pol) and of comparatively smaller size metallic VA (MVA) structure with slotline-to-coax-balun feed. Aluminium metal is used for fabricating monolithic linear arrays positioned together to form a 2D-array. The thickness of MVA reduces the inter-rows gap, thereby removing the impedance anomalies. A Floquet model-based analysis with FEM is used for analysing MVA’s performance in an array environment validated with measurements in an 8 × 8 finite array environment. The measurements demonstrate wide beamwidth (>90o;120o), impedance and pattern bandwidth of 127% and 60%, gain >3dBi and x-pol level <−20 dB.