A compact monopole array with decoupled ports

In compact arrays, tight element spacing results in strong mutual coupling. This may cause severe system performance degradation. The effects of the coupling can be alleviated through the introduction of a decoupling network. An alternative solution comprises of a multi-port feed network which excites the antenna elements in accordance with the eigenvectors of the scattering parameter matrix of the array. This paper describes the design of a novel 4-element monopole array. The modal feed network of the array is implemented as a planar ring-type circuit in stripline with four coupled line sections. This implementation offers a significant reduction in size, resulting in a very compact adaptive array.