Space and Position Management of Wideband Conformal Vivaldi Antenna Array With Sidelobe Reduction

This work systematically studies conformal Vivaldi antenna (VA) arrays in a spherical volume. A VA with gain varying from 5 to 9 dBi and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11} \leq -10$ </tex-math></inline-formula> dB from 4.3 to 9.8 GHz is considered. A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \times 7$ </tex-math></inline-formula> VAs are placed on a correctional area of the cylinder to scan from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta = 0^{\circ}$ </tex-math></inline-formula> to 45° at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\phi = 90^{\circ}$ </tex-math></inline-formula>. The results show that the sidelobe level (SLL) has a higher amplitude, almost equivalent to the main lobe. To reduce the SLL, the phase center to phase center distance of antenna elements is reduced by bringing the radius correctional area of the cylinder leading to the development of a modified VA (MVA) without disturbing the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> parameters of the VA. To verify, the MVA as a radiating element a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1 \times 7$ </tex-math></inline-formula> circular MVA array is developed with the same scanning capability, the results show a high reduction of SLL. Finally, a 49-element MVA array arranged in a spherical volume is developed to obtain 3-D-beam scanning. The antenna elements are designed to be conformal to the periphery of a sphere to achieve a 360° beam scanning in the azimuthal plane and ±45° in the elevation angle. The 3-D array has a realized gain of 18.57 dBi at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta = 0^{\circ}$ </tex-math></inline-formula> and an approximately 10 dB difference in the magnitude of the major lobe and side lobe levels at all the scan angles. The validation is carried out using ANSYS HFSS full wave solver and achieved a good agreement with the theoretical considerations.