Improved nested array with hole-free DCA and more degrees of freedom

A new linear sparse array based on the nested array is proposed, which enjoys all the good properties of the two-level nested array, and can provide more degrees of freedom (DOF). The new array is constructed by two uniform linear arrays (ULAs) and an additional sensor. The sensor locations, the array aperture, and the achievable DOF from its difference co-array (DCA) are all benefited for closed-form expressions. Furthermore, the resulting DCA is kept as a hole-free ULA. The optimal numbers of sensors in the two ULAs provided the total number of physical sensors are derived. This new array can resolve more sources and achieve better angle estimation performance than the two-level nested array. Simulation results validate these conclusions.