Modern phased array applications, such as 5G, are imposing ever growing constraints and requirements on phased arrays. These include the need
for multiple functionalities, larger bandwidth, higher reconfigurability, smaller size, lower weight, and reduced costs. Regularly spaced digital phased arrays, in which the radiating elements are arranged on a regular lattice, and each element is equipped with an independent T/R module and a digital channel, result in high cost and complexity.
In this context, this tutorial focuses on irregular phased array, in which the number of degrees of freedom for beam-forming is reduced (e.g., the element locations are sparse and the digital channels are implemented at the sub-array level). Starting from a theoretical overview of irregular array, with a focus on sub-arrayed architectures, and on their impact on the radiation performance, novel design methods based on polyomino-tiling strategies and AI will be presented together with recent technological advances enabling their low-cost manufacturing and assembly.