A Wide-Angle Scanning Linear Array with Low-Profile Ungrounded Highly Directive Element

This letter presents a novel approach to enhance the scanning range of linear array by employing a highly directive antenna element with ungrounded and low-profile characteristics. The proposed antenna element consisting of two closely spaced dipoles realizes a good front-to-back ratio (FTBR) by adjusting the space and phase difference between the dipoles. A balun feeding structure is utilized to achieve impedance matching of the closely spaced dipoles. The proposed antenna element demonstrates an impressive half power beamwidth (HPBW) of up to 162°. Consequently, a 1×8 linear array along the H-plane is designed based on the proposed antenna element. U-shaped branches are incorporated to simultaneously suppress mutual coupling and broaden the element HPBW. A prototype of this array operating at X-band is fabricated and measured, achieving a scanning range of ±80° with sidelobe level lower than -10dB and low gain fluctuation. This low-profile ungrounded antenna array achieves wide-angle scanning, providing good potential for application on conformal platforms.