Compact circular connected monopole antenna arrays for wideband MIMO applications

Abstract

In this work, a connected circular monopole antenna array is presented for ultra-compact, wideband, multiple-input multiple-output (MIMO) wireless access point applications. Two configurations of the circular array are considered; one with 4- and another with 8-antenna elements using the same substrate size. The frequency bands covered were from 2.3 to 5.3 GHz (LTE 2.3-3.8 GHz, Bluetooth 2.4 GHz, wireless local area network 2.4, 5.2 GHz and WiMax 2.3 GHz). The obtained measured bandwidth was 3 and 2 GHz for the 4- and 8-element arrays, respectively. The antenna system is fabricated on a commercially available Roger 4350 substrate with εr equal to 3.5 and height of 1.52 mm. The radius of the array is 32 mm (the most compact with wideband characteristics). The length of a single element is only 15 mm which is λ/8 at the lowest frequency. The design is planar, low profile and very compact. Good MIMO performance is achieved.