Orthonormal Method for Compact Global Navigation Satellite Systems Antenna Array Designs

Abstract

Compact antenna arrays require special considerations at design time not to degrade its efficiency and also the spatial diversity becomes reduced in terms of phase resolution as distance diminishes. Additionally, element radiation patterns are affected and the objective of equally behaved antennas is even more difficult to achieve. However, the induced antenna gain differences can actually be helpful because they can be used to maintain the degrees of freedom in array radiation pattern subspace. In this article, a general analysis on the relationship of efficiency and beam patterns are reviewed to prove that maximum efficiency is achieved when radiation patterns fulfill a given orthogonality condition. Under this condition, we propose to apply a unitary matrix transformation to the array response that can translate the compact antenna array behavior into the equivalent response of a λ/2‐spaced ideal antenna array without modifying its total efficiency. Consequently, an useful compact antenna array should be designed to have orthogonal radiation beams. Then, applying the transformation, they can be translated to another orthogonal radiation patterns set with only phase differences and a common gain pattern. Simulated results of a computer‐aided design of a practical array of Global Navigation Satellite Systems microstrip antennas are presented.