Wideband characteristics of Vivaldi antenna arrays

Over the past two decades, Vivaldi antenna arrays have proven to be versatile solutions for wideband, widescan phased array systems, providing 10:1 bandwidth, or more, with 45 degree scan range. The increasing demand for using Vivaldi antenna arrays in diverse, high-performance systems creates the need to explore new concepts under new perspectives, three of which are addressed here: modularity, low-profile and dispersion. Modularity introduces a discontinuity in the E-plane that is disruptive to performance in finite as well as infinite arrays. The effect of this discontinuity is studied in greater detail in infinite arrays with modularity of elements and sub-arrays. Based on the underlying physics the severe resonances observed are characterized, and it is concluded that for very large arrays compartmentalization into large sub-arrays mitigates these detrimental effects while achieving some modularity. Earlier work has shown that dielectric permittivity aids in designing shorter antennas with good bandwidth; here, a new approach utilizing a dielectric cover at the array aperture to improve bandwidth for short antennas is proposed. The technique employs covers of moderate thickness and ensures good match at broadside and scan for an otherwise poorly-matched short Vivaldi element. A framework for analyzing wideband dispersion in antenna arrays is introduced. It is observed that well-matched Vivaldi antenna arrays demonstrate low-dispersion qualities comparable to other well-known wideband arrays, and thus may serve as prime candidates for short pulse transmission systems