Ultra-wideband small modular array antenna based on column-coupled Vivaldi subarrays

In this contribution an ultra-wideband small array antenna for direction-of-arrival (DOA) estimation in low-cost industrial radar applications operating in the frequency range from 5 GHz-8 GHz is designed by using column-coupled Vivaldi subarray modules. Compared to traditional ultra-wideband antenna arrays consisting of inherently wideband antenna elements, the proposed design procedure utilizes mutual coupling (MC) across the antenna elements to reduce the antenna element size, to simultaneously improve the subarray module return loss, and to allow for relatively small element spacing in the plane of DOA estimation. In contrast to state-of-the-art tightly-coupled ultrawideband antenna arrays consisting of a large number of very small array elements on a regular grid-spacing, the proposed solution only relies on MC across four antenna elements along each array column. It hence provides UWB characteristics with a small number of antenna elements, it can easily be interfaced with a low-cost 4-RX channel radar fronted and allows for arbitrary linear array geometries such as non-uniform element spacing optimized for DOA estimation. We characterize the array and discuss MC aspects and DOA estimation results based on measured array data.