Within this study, an optimized ultra-wideband (UWB) multi-input multi-output (MIMO) antenna incorporating band-rejection features is introduced for wireless application. The proposed design comprises four circular single-element antenna units that are designed on a Rogers RT/duroid 5880 (tm) support material having an overall size of 80 × 80 × 0.8 mm3 or 0.72λ0 × 0.72λ0 × 0.0072λ0 (λ0 is the free-space wavelength at lowest frequency 2.7 GHz) and positioned perpendicularly. To enhance isolation, cross-shaped extensions are incorporated. Measurement results indicate that this antenna demonstrates an impedance bandwidth of −10 dB, spanning from 2.7 to 11.67 GHz (125%) and penta-notched filters for 3.2–4.0 GHz, 4.49–5.05 GHz, 5.56–6.16 GHz, 8.23–8.56 GHz, and 10.29–11.53 GHz. The presented antenna is capable of filtering signals from WiMAX (3.3–3.7 GHz), N79 band (4.8–4.9 GHz), WLAN downlink (5.725–5.825 GHz), ITU-R (8.275–8.5 GHz) and Ku-band downlink (10.7–11.2 GHz). The antenna exhibits envelope correlation coefficients (ECC) below 0.04 and provides isolation superior to 20 dB. Experimental results indicate that the simulated characteristics closely match the measured ones. The developed MIMO antenna demonstrates strong suitability for ultra-wideband (UWB) wireless communication applications.

In this paper, a novel design of ultra-wide stop-band single-side single-layer frequency selective surface (FSS) is presented. The unit cell of the proposed FSS is designed using the combination of conventional square loop and cross (CSLC). To enhance the bandwidth of this structure, an additional cross is inserted in all the four quadrants of CSLC. The stop-band transmission bandwidth assuming −10 dB threshold is found to be 128.94% (2.16–10 GHz) which is 34.33% more as compared to the bandwidth of CSLC. The unit cell with a dimension of 16 × 16 mm2 is printed on one side of an FR4 substrate. The design is fabricated and the measured results are found to be in good agreement with the simulated results. The design provides excellent stability for both transverse magnetic and transverse electric polarizations. The design is very flexible, where any resonant frequency can be achieved by changing the length of unit cell. The design is useful in many applications such as antenna gain enhancement, electromagnetic wave shielding for Wi-Fi/5G systems, and other Internet of Things-based applications.