New sparse array for non‐circular sources with increased degrees of freedom

Abstract

Recently, sparse arrays have received considerable attention as they provide larger array aperture and increased degrees‐of‐freedom (DOFs) compared to uniform linear arrays. These features are essential to enhance the direction‐of‐arrival estimation performance. However, most of the existing sparse arrays are mainly designed for circular sources and realize limited increment in DOFs for non‐circular sources. In this letter, a new sparse array configuration for non‐circular sources is presented, which significantly increases the achievable DOFs and improves the direction‐of‐arrival estimation performance. The proposed geometry comprises two effectively configured uniform linear arrays that exploit the characteristics of non‐circular sources and extend the array aperture. For a given number of sensors, its virtual array is advantageously a hole‐free uniform linear array. Moreover, the precise sensor locations, achievable DOFs, and optimal distribution of physical sensors are determined analytically by closed‐form expressions. Owing to these benefits, the proposed array efficiently resolve multiple sources in under‐determined conditions and achieves better direction‐of‐arrival estimation performance than its counterpart structures. Simulation results validate the superiority of the proposed configuration.

A super transformed nested array with reduced mutual coupling for direction of arrival estimation of non‐circular signals

“…In the first simulation, we perform a DOFs comparison between STNA and NA [8], NADiS [30], DsCAMpS [28], CASFS [29], TNA [31], ETNA [33], NSANCS [32]. Table 3 lists the number of DOFs of the nine kinds of sparse arrays.…”

“…In Ref. [32], a new sparse array for NC sources (NSANCS) is proposed, which has the same virtual array as TNA‐I, but the number of sensors in compact sub‐arrays is smaller. However, similar to the NA, there exists a dense sub‐array in the structure of NADiS, TNA‐I, and NSANCS, which means a serious mutual coupling effect.…”

Triad-Displaced ULAs Configuration for Non-Circular Sources with Larger Continuous Virtual Aperture and Enhanced Degrees of Freedom

“…However, this design lacks implementation for an odd number of sensors. A novel sparse array for NCS (SANCS) was designed for the DOA estimation of NCS [39], which offers more DOF than the aforementioned sparse arrays. However, the physical locations in the SANCS array are determined through an exhaustive search algorithm.…”

“…A new SANCS (NSANCS) [40] benefiting from closed-form expressions was recently introduced to obtain a hole-free resulting ULA with a higher DOF capacity for NCS. Although the NSANCS design [40] addresses the major limitation of the SANCS array [39] by formulating analytical expressions for element positions and achievable DOF, there is still room for improvement in terms of uDOF and coarray aperture for NCS. Thus, it develops the pursuit of constructing a more robust sparse design for NCS that can provide a larger continuous virtual aperture and enhanced DOF capacity.…”

“…The Tdis-ULAs structure for NCS possesses all the useful properties, such as a virtual array of larger continuous aperture and a hole-free ULA. Unlike SANCS [39], it uniquely determines the physical sensor locations through analytical expression. While the other parameters for array configuration, including the inter-ULA displacement, the optimal distribution of physical sensors among the ULAs, and the number of uDOF, also benefit from closed-form expressions.…”