Compact multiport antenna with isolated ports

Abstract

The small element spacing of compact multiport arrays introduces strong mutual coupling between the antenna ports. Because of this coupling, the input impedance of the array changes when elements excitations are varied, and consequently, the array cannot be matched for an arbitrary excitation. Decoupling networks have in the past been used to provide an additional connection between antenna ports to cancel the coupling between elements. An alternative approach is to design the antenna so that each port does not excite a single element, but instead all elements simultaneously. The geometry of the antenna is optimized so that this direct excitation of elements counteracts the mutual coupling, thus, yielding decoupled ports, This article describes the design of such a four-port antenna. © 2007 Wiley Periodicals, Inc.