On the Merit of Asymmetric Phased Array Elements

Abstract

Phased array antennas with a desired symmetric scan range about broadside usually are designed with array elements that have a corresponding symmetry. However, this appears to be an unnecessary restriction. We 1) show analytically that symmetric scan performance normally is maintained even with asymmetric array elements, and 2) compare conventional symmetric patch elements, which have <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$E$</tex></formula> - and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$H$</tex></formula> -plane symmetry, with patches which are asymmetric in the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$E$</tex></formula> -plane, and with fully non-symmetric patches which have neither <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$E$</tex> </formula> - nor <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$H$</tex> </formula> -plane symmetry. The comparison is based on patch designs obtained by numerical optimization, over a 90 degree scan volume and 3:1 bandwidth, using a genetic algorithm. The elements with spoiled symmetry clearly have better scan and/or bandwidth performance. The results support our view that spoiling the symmetry may be a general technique to improve the bandwidth of phased array elements.