A new ultra-wideband tightly coupled monopole array (TCMA) is introduced. Namely, the unit-cell of our TCMA consists of a modified monopole element, which is capacitively coupled to two grounded vias. Notably, both the common-mode and loop-mode resonances are pushed out of the operating frequency band of our array, while the well-known broadside null found in the radiation pattern of traditional monopole antennas is entirely eliminated. In addition, to improve the scanning bandwidth of our array, a dielectric superstrate is accordingly utilized. The proposed antenna array is extremely low profile with a maximum thickness of 0.4λH. Infinite array simulations of our antenna array demonstrate a bandwidth of 3:1 (33 GHz to 101 GHz) with VSWR<3 for a maximum scan-angle of ± 45◦ for all principal E-, H- and D-planes.
