Simplification and Implementation of Decoupling and Matching Network With Port Pattern-Shaping Capability for Two Closely Spaced Antennas

A simple U-shaped decoupling and matching network (DMN) with port pattern-shaping capability is presented for two closely spaced antennas. When the antennas are identical and symmetrically positioned, we prove that the port pattern remains unchanged, although an infinite number of U-shaped DMNs can be designed. Subsequently, two methods are proposed to enable port pattern-shaping capability without changing the antennas, i.e., changing the impedance matrix by adding a cross network between the antennas, and by introducing asymmetry to the U-shaped DMNs. These methods offer more freedom to the compact antenna system design especially in terms of pattern shaping.