A compact highly isolated two- and four-port ultrawideband Multiple Input and Multiple Output antenna with Wireless LAN and X-band notch characteristics based on Defected Ground Structure

A novel two- and four-port antenna structure are proposed to achieve improved isolation and operate in the ultrawideband (UWB) frequency range. The projected designs comprise a hybrid circular and rectangular embedded UWB antenna with a partial ground plane. The alteration of the radiating and ground planes modifies the current flow and aids in realizing a broader bandwidth. The dual-band notches are created on UWB using slot and stubs. The U-shape slot on the feedline neutralizes the current flow at 5.2 GHz, and a pair of symmetrical H-shape stubs across the feedline couples the current flow from the feedline to stubs at 7.4 GHz frequency, and negligible current reaches the radiator. The dual-band notch UWB antenna is reproduced to create two-port and four-port MIMO antennas with a less than quarter wavelength spacing. Using a deficient ground structure, better isolation between the interelements is achieved. The projected two- and four-port design has overall physical geometry of 0.2λ × 0.4λ × 0.02λ and 0.5λ × 0.4λ × 0.02λ and provides a measured impedance bandwidth between 3.3–12.8 and 3.1–12 GHz, respectively. The distinctive feature of both antenna designs is incorporating simple and effective defective ground structures as decoupling structures in the ground plane to generate better than 25 dB isolation across the operational spectrum. The current between the interelement is suppressed via the ground plane, leading to mutual coupling reduction. In addition, complete MIMO diversity parameters and time-domain characteristics are explored, and the findings show that the proposed designs are appropriate for wireless applications.