An Extremely Wideband Tightly Coupled Dipole Array With Shared-Aperture Configuration

The intent of this letter is to expand the tightly coupled dipole array (TCDA) concept in a shared-aperture configuration for high radiation efficiency and extremely wide bandwidth. Specifically, a high-band TCDA is deployed beneath the aperture of a low-band TCDA. With this configuration, the profile height keeps the same as that of a stand-alone low-band TCDA. It offers a thin ?(L)/13.7 (or 1.7?(H)) array with 23.2:1 bandwidth for active voltage standing wave ratio (VSWR) < 3, where ?(L) and ?(H) are the wavelengths at the lowest and highest frequencies of the operating frequency band. Although the shared-aperture configuration is profit for low profile and bandwidth extension, it causes cross-band coupling and deteriorates radiation performance. To solve this issue, the low-band TCDA is designed to be electromagnetic transparent to the high-band electromagnetic waves. The two TCDAs become immune to the cross-band interference and operate properly as in their stand-alone cases. An array prototype consisting of a 16 x 16 high-band array and an 8 x 8 low-band array is fabricated and measured. The measured radiation efficiency is demonstrated to be 77% on average across a 23.2:1 bandwidth.