Antenna-Array Network Model

An antenna can be modeled as a two-port network using S-parameters. However, having individual antenna S-parameters is not sufficient for modeling an array of antennas as antennas exhibit mutual coupling. This article proposes a network model to represent an antenna array with mutual coupling. Using the proposed model, an N-element antenna array is modeled as a combination of two-port networks representing each element and an N-port network representing mutual coupling. Two techniques to calculate mutual coupling S-parameters are presented: a primary method using numerical solutions and an approximate method using approximate expressions. The proposed model was validated using four monopole arrays having different interelement spacings, the number of elements, and nonidentical antennas.

I. Introduction

Antenna arrays are widely used across many fields: from radars [1]–[4] to mobile communication systems [5]–[10] to radio astronomy [11]–[15]. They offer many advantages over single antennas: high gain, high directivity, and the capability to steer the beam [16], [17]. However, arrays are more complex and more difficult to design due to mutual coupling than individual antennas [18].