Density-Tapered Sunflower: A Deterministic Sparse Array Solution [Cover]

Front cover image_ The front cover shows an example of distribution of λ-wide elements in a density-tapered sunflower array with radius = 30λ (top left). The tapering function is a Blackman window. The element pattern design was based on the Fermat’s spiral, according to a deterministic, aperiodic, and balanced positioning procedure with the goal of guaranteeing uniform performance over a wide range of steering angles. The spatial density modulation of the elements increases the probe sensitivity while simplifying the design of the transmit section, which does not need element-dependent amplitude control. The other panels show artistic renderings of simulated one-way fields radiated by the tapered sunflower array: without steering (top right), with (32°,0°) steering (bottom left), and with (32°, 32°) steering (bottom right). The fields were evaluated on the spherical cap passing through the focus (radius = 120λ). The images highlight that, because of the aperiodic distribution of the elements, the grating lobe energy is almost homogeneously spread in space. For further reading, please see the accompanying article on page 1580 of this issue