Synthesis of Wide-Angle Difference Pattern with Low Side-lobe Level on Asymmetric Aperture of Hemispherical Conformal Array Antennas

In this paper, an approach to the synthesis of the wide-angle scanning difference pattern with low side-lobe level (SLL) on an asymmetric aperture of the hemispherical conformal array antennas (HCAA) is proposed. It's hard to synthesize the difference patterns for a HCAA due to its asymmetric radiation aperture when the scanning angle reaches a large value, such as
$\theta=90^{\circ}$
. This asymmetry is not only reflected in the axial directions of the elements but also in the distribution of the elements' positions. A modified differential evolution (DE) method based on the K-means clustering is presented to optimize the difference pat-terns with low SLL for the asymmetric aperture of a HCAA. As an example, the difference patterns along the elevation direction with −20 dB SLL and −37.7 dB null depth when
$\theta=90^{\circ}$
and −22 dB SLL and −43.9 dB null depth when
$\theta=75^{\circ}$
are synthesized on a HCAA with 176 elements.