GA-Aided Directivity in Volumetric and Planar Massive-Antenna Array Design
share
The problem of directivity enhancement, leading to the increase in the directivity gain over a certain desired angle of arrival/departure (AoA/AoD), is considered in this work. A new formulation of the volumetric array directivity problem is proposed using the rectangular coordinates to describe each antenna element and the desired azimuth and elevation angles with a general element pattern. Such a directivity problem is formulated to find the optimal minimum distance between the antenna elements d_min aiming to achieve as high directivity gains as possible. An expedited implementation method is developed to place the antenna elements in a distinctive plane dependent on (θ_0; ϕ_0). A novel concept on optimizing directivity for the uniform planar array (OUPA) is introduced to find a quasi-optimal solution for the non-convex optimization problem with low complexity. This solution is reached by deploying the proposed successive evaluation and validation (SEV) method. Moreover, the genetic algorithm (GA) method was deployed to find the directivity optimization solution expeditiously. For a small number of antenna elements , typically N∈ [4,…, 9], the achievable directivity by GA optimization demonstrates gains of ∼ 3 dBi compared with the traditional beamforming technique, using steering vector for uniform linear arrays (ULA) and uniform circular arrays (UCA), while gains of ∼1.5 dBi are attained when compared with an improved UCA directivity method. For a larger number of antenna elements , two improved GA procedures, namely GA-marginal and GA-stall, were proposed and compared with the OUPA method. OUPA also indicates promising directivity gains surpassing 30 dBi for massive MIMO scenarios.
READ FULL TEXT