Number Of Consecutive Lags Research Articles

Sparse Billboard and T-Shaped Arrays for Two-Dimensional Direction of Arrival Estimation

In two-dimensional direction of arrival (2D-DOA) estimation, planar arrays can estimate the elevation and azimuth angles simultaneously. However, many planar array topologies such as billboard, L-shaped, T-shaped, and 2D nested arrays suffer from mutual coupling that results from the small separation between the physical sensors (antennas), which limits the estimation capability of the sensor array. In an attempt to reduce mutual coupling between sensors, this article proposes sparse billboard and T-shaped arrays in which the number of closely separated sensors is significantly reduced. In addition to extending the CRB for fourth order coarray, this article also derives closed-form expressions for the sensor locations and the number of consecutive lags or the uniform degrees of freedom (uDOF), in the fourth-order difference coarray (FODC). Simulation results demonstrate the robustness of the proposed sparse arrays against mutual coupling.

The Design of A Novel Sparse Array Using Two Uniform Linear Arrays considering Mutual Coupling

The sparse arrays using two uniform linear arrays have attracted considerable interest due to the capability of giving analytical expression of sensor location and owning robust direction‐of‐arrival (DOA) facing strong mutual coupling and sensor failure. In order to achieve the maximum consecutive virtual uniform linear array in difference coarray, in this paper, a design method of a novel sparse array using two uniform linear arrays (NSA‐U2) is proposed. We first analyze the relationship between the values of displacement of two subarrays and difference coarray, and then we give the analytical expressions of the displacement and the number of consecutive lags. By discussing the selection of number of subarray sensors, the design of NSA‐U2 is completed. Moreover, through choosing a proper compressed interelement spacing, NSA‐U2 can be robust to mutual coupling effect. Numerical experiments prove the effectiveness and favorable performance of DOA estimation with mutual coupling.

Achievable degree-of-freedom for three-level prime arrays

Due to their large aperture size, coprime arrays are good candidate in the presence of mutual coupling as most of the elements are separated by more than half-wavelength. However, the number of consecutive lags in their difference coarray is limited. Combining three uniform linear subarrays where the number of elements in the subarrays are pairwise coprime integers overcomes this limitation. The resultant array is referred to as three-level prime array (3LPA). The 3LPA has a closed form expression for antenna locations and can improve the DOF using smaller aperture size compared with coprime arrays. In this paper, we derive an approximate expression for the achievable DOF for the 3LPA configuration. Simulation results confirm the validity of the derived expressions compared with the exact DOF.

Thinned Coprime Array for Second-Order Difference Co-Array Generation With Reduced Mutual Coupling

In this work, we present a new coprime array structure termed thinned coprime array (TCA), which exploits the redundancy in the structure of existing coprime array and achieves the same virtual aperture and degrees of freedom (DOFs) as the conventional coprime array with much fewer number of sensors. In comparison to other sparse arrays, thinned coprime arrays possess more unique lags (total number of difference co-arrays) than the nested arrays, while the number of consecutive lags (connected co-arrays) generated is close to 75% of the consecutive lags of the nested arrays with hole-free co-arrays. The resulting structure is much sparser and the number of sensor pairs with small separation is significantly reduced. Theoretical properties and proofs are provided and simulations are presented to demonstrate its robustness against heavy levels of mutual coupling using compressive sensing based direction of arrival estimation as well as certain additional desirable characteristics.

Generalized Super-resolution DOA Estimation Array Configurations’ Design Exploiting Sparsity in Coprime Arrays

Higher degrees of freedom (DOF) for direction of arrival can be attained by using coprime arrays. In this paper, we design super-resolution generalized coprime array configurations based on suppression and displacement to achieve higher DOFs. The first composition known as CASDiS stands for coprime arrays with suppressed and displaced subarrays. This structure can achieve \( 4MN + 1 \) number of consecutive lags considering only \( 2M + N \) number of sensors. However, still there are some holes. In order to achieve hole-free lags, a novel nested inspired “Nested Displaced CoPrime subarrays” (NesDCoP) structure is designed. This configuration performs remarkably in terms of generating consecutive lags and can triumph hole-free \( 4MN + 2M + 1 \) lags. The key contributions of this work are as follows: Firstly, both array configurations can achieve longer consecutive lags as compared to previously proposed arrays. Secondly, NesDCoP structure can accomplish consecutive lags almost equivalent to nested arrays. Lastly, both structures are less complex because there is no need to use interpolation techniques. The practicality of these configurations is demonstrated using MUSIC algorithm, and then, simulation results are equated with other methods which show the effectiveness of both the proposed array configurations.

An improved expanding and shift scheme for the construction of fourth-order difference co-arrays

Abstract An improved expanding and shift (IEAS) scheme for efficient fourth-order difference co-array construction is proposed. Similar to the previously proposed expanding and shift (EAS) scheme, it consists of two sparse sub-arrays, but one of them is modified and shifted according to a new rule. Examples are provided with the second sub-array being a two-level nested array (IEAS-NA), as such a choice can generate more fourth-order difference lags (FODLs), although with the same number of consecutive lags. Furthermore, the array aperture of IEAS-NA is always greater than the corresponding EAS structure, which helps improving the DOA estimation result. Simulations results are provided to show the improved performance by the proposed new scheme.