Ultra wideband one-dimensional linear array based on tightly coupled structure

In this paper, an ultra-wideband tightly coupled antipodal Vivaldi antenna array, distributed in one dimension along the E-plane, was designed based on a tightly coupled structure and parallel feeding method. The antenna elements comprise radiation sections and balun sections, achieving a voltage standing wave ratio (VSWR) less than 2 across the operational frequency range of 2 GHz to 18 GHz, thus realizing a bandwidth of up to nine octaves. These antenna elements were extended in one dimension along the E-plane, while being fed in parallel through two cascaded 1-to-4 power dividers, resulting in sixteen-way power distribution networks. Consequently, an ultrawideband one-dimensional tightly coupled microstrip antenna array was obtained. Within the operating frequency band from 2 GHz to 18 GHz, the VSWR of the one-dimensional antenna array was kept below 3, with a maximum value reaching 2.6. The gain of the one-dimensional antenna array ranged from 6.5 dBi to 17 dBi. Due to the characteristics of small element spacing and ultra-wideband performance demonstrated by the tightly coupled antenna array designed herein, it is anticipated that this design can be applied to antenna arrays with a greater number of elements in the future.