Analysis of infinite arrays of arbitrarily shaped planar radiating elements using a Floquet mode based Method of Moments approach

Large phased array antennas are theoretically capable of delivering the directive gain of similarly sized aperture antennas while offering electronic beam scanning capabilities and greater operational flexibility. Unfortunately, the high cost associated with large phased antenna arrays has limited their use to highly specialized applications where no other antenna system configuration is possible. The recent development of less expensive microwave active devices has led to a renewed interest in large phased antenna arrays. These devices allow the amplification and signal processing required in phased antenna arrays to be distributed among many identical modules which combine the amplification, feed network, and radiating element sections of traditional antenna arrays. These modules can then be produced at a lower unit cost and result in an antenna system which is more easily integrated and repaired.

The practicality of large phased antenna arrays is still limited by the great difficulty experienced in predicting their performance. Mutual coupling effects between the radiating elements produce significant variations from ideal array theory. The prediction and reduction of these effects requires a characterization approach which is computational rather than experimenta1. This document presents a new approach which allows the characterization of arbitrarily shaped planar radiating elements printed on a dielectric support slab backed by a perfect electric conductor ground plane. This analysis approach uses a Method of Moments technique to determine the electric current distribution over a set of bi-triangular sub-domain elements describing a single radiating element. The effects of mutual coupling in the fully active infinite antenna array are included in the analysis by a Floquet mode based Green's function used in the Method of Moments analysis. This characterization technique has been implemented in the computational electromagnetics code ASIA (Analysis Software for Infinite Arrays), The analysis approach presented here is validated by comparison with published input impedance data for two different radiating elements. Finally, preliminary analysis results are shown for a more complex radiating element.