Computationally Optimized MIMO Antenna with Improved Isolation and Extended Bandwidth for UWB Applications

Isolation and bandwidth are the two important performance parameters of the multiple-input-multiple-output (MIMO) antenna. A small footprint of an antenna with enhanced isolation and extended bandwidth is highly desirable for space-limited UWB applications. In this paper, we present a compact and computationally optimized MIMO antenna for UWB applications. The proposed antenna consists of two micro-strip-fed semicircular radiating elements. The inverted prism-shaped ground stub is used to enhance isolation. A truncated-shaped partial ground plane with two ground slots is used for impedance matching over the extended UWB. The circular monopole radiating elements of the reference antenna (RA) are converted into semicircular radiating elements for efficient utilization of the available space. The initial design parameters are obtained from the RA. In the next step, the initial design parameters are optimized by a fast and accurate surrogate-assisted optimization model. Using the optimized design parameters, the final design of the antenna is simulated using a computer simulation tool. The prototype of the antenna is fabricated on a Roger substrate (substrate height 'h' = 0.8 mm) with a dielectric constant of 3. The manufactured prototype with the size of 31 x 18 mm(2) is experimentally evaluated and validated using vector network analyser and anechoic chamber. The proposed MIMO antenna provides extended ultra-wide impedance bandwidth of 3-25 GHz (fractional bandwidth 157%), enhanced isolation S-21 <= - 27 dB envelope correlation coefficient (ECC = 0.002), good pattern diversity, and constant group delay. Finally, the obtained results are compared with the existing literature.