Dual-Polarized Vivaldi Array on a Triangular Lattice

This article presents a dual-polarized Vivaldi array on a triangular lattice. The all-metal ultrawideband Vivaldi features offset radiator pairs that are precision-machined from aluminum stock as a modular tile, similar to earlier reports on more typical all-metal square-lattice Vivaldi arrays. The intent of this work is to validate the embedded element performance of the dual-polarized triangular-lattice Vivaldi, comparing one-to-one with results for a similarly sized dual-polarized all-metal Vivaldi array on a square (egg-crate) lattice, reported previously. The triangular-lattice Vivaldi array is optimally sampled for grating-lobe-free scans with a potential 15.5% reduction in element count compared to a corresponding optimally sampled square-lattice array of similar size. As such, the footprint of the manufactured triangular-lattice Vivaldi array is roughly 8% larger than the square-lattice array, yet has 7% fewer elements. Infinite array predictions are presented and shown to compare favorably with previous findings for the square-lattice Vivaldi array, noting minor performance compromises. Wideband and wide-scan simulations are validated with measurements of prototype hardware, demonstrating that embedded element performance of the triangular-lattice array correlates well with modeling predictions. All told, the triangular-lattice array has similar capability to the square-lattice Vivaldi array in a more efficiently sampled aperture.

I. Introduction

Phased antenna arrays are potentially the most versatile and consequently the most expensive type of electromagnetic sensor [1]–[4]. In large part, cost can be directly tied to the size of the array, or more precisely the total number of elements in the array, making it important to use the minimum number of elements required to satisfy cost-sensitive applications. A survey of the literature will reveal that the vast majority of planar, 2-D array apertures are in fact based on a square lattice, as it is generally the simplest for construction, has the appeal of geometric symmetry, and so on. Yet, though the square array lattice is the most common in practice, it is well known that an optimally sampled triangular lattice can achieve an additional 15.5% reduction in array element counts over the optimally sampled square lattice with the same aperture area and grating-lobe-free scan operation [3]–[6]. Very large phased arrays (or more precisely, phased arrays with large element counts) favor triangular lattices for this reason. As an example, the famous Precision Acquisition Vehicle Entry Phased Array Warning System (PAVE PAWS) is a very large array of dual-polarized dipole radiators benefiting from the lower element counts of a triangular grid [7].