A compact printed extremely-wideband MIMO antenna with WLAN band rejection

A printed MIMO antenna with extremely wide-band (EWB) for multi-band wireless applications has been proposed and analyzed in this paper. The designed antenna satisfies the voltage standing wave ratio (VSWR) requirement of less than 2.0 in an extremely wide frequency band ranging from 2.7 GHz to 20 GHz. To enhance the isolation coefficient in MIMO antenna, two parallel strips are added between two radiating elements. Consequently, the mutual coupling coefficient is much below -15 dB for all operating frequency band. In addition, since the bandwidth of this antenna covers frequency bands where several applications and/or services may be simultaneously acting in the considered area, it becomes a very important feature the capability of rejecting the interferences occurring between these systems. In this paper, the introduction of suitable slots as an effective method for sub-band notching has been presented, and, as an example, the WLAN band rejection has been considered in detail. By exploiting the optimization possibilities introduced by the slot structure degrees of freedom, it became possible to obtain the desired band rejection. All the here considered structures have been designed choosing for the substrate the popular FR4, with dielectric constant of 4.4, and thickness 1.6 mm.