Dual-beam filtering patch antennas

This paper describes a design methodology for five dual-beam filtering patch antennas and their applications to ultra-wideband (UWB) multiple-input multiple-output (MIMO) system. Structures of the five dual-beam filtering patch antennas are the same, but their sizes are different for covering different operation band. With a metal strip and two slots, a wide impedance bandwidth with a stable symmetrical dual-beam radiation pattern is obtained by the patch antenna, and two controllable radiation nulls at the lower and the upper band edge, respectively, are produced, ensuring a sharp roll-off rate at the band edges for both reflection coefficient and realize gain. Five dual-beam filtering patch antennas operating at 3.0–3.8, 3.8–4.8, 4.8–6.15, 6.15–7.98, and 7.98–10.76 GHz, respectively, are applied in a five-element MIMO antenna for covering the whole UWB band (3.1–10.6GHz), and their filtering performances can help to improve the isolation among the different antenna elopements.