Range-angle-dependent beamforming with FDA using four-dimensional arrays

By virtue of its low sidelobe and multibeam pattern characteristic, four-dimensional time-modulated array (TMA) has been attracting considerable attention. Recently, a novel frequency diverse array (FDA), with flexible beam scanning characteristic, has been proposed. So far, TMAs and FDAs are investigated separately, but their integration which may possess both advantages has rarely been reported in the literature. In this paper, a new range-angle-dependent time-modulated frequency diverse array (TMFDA) is proposed. By introducing time-modulated radio frequency switches into the beamfoming network of an FDA, TMFDA can achieve range-angle-dependent patterns, both at the carrier frequency and at the sidebands. Additionally, TMFDA has a unique advantage in that its beam direction of the sidebands can be tuned by the pulse duration, switch-on instant and frequency shift, which offers greater design freedom, enabling better performance and a reduction of hardware requirements over FDA. Moreover, the TMFDA has low sidelobe and multibeam pattern characteristic in the joint range and angle domains. Numerical results are presented to validate the superiority of TMFDA characteristics in terms of achieving low sidelobe level, low sideband level and multibeam beamforming.