# Antenna Designs for 5G/IoT and Space Applications
## 2 Short Presentation of the Papers
The measure and simulated results are in good agreement and the proposed antenna array provides a dual band with a narrow beamwidth and a small reflection coefficient, wide \(-10\) dB impedance bandwidth (e.g., 26-38.5 GHz) and radiation efficiency of 95%. [PERSON] et al. [7] proposed a low-profile meandered loop slot-line antenna for the Internet of Things (IoT) application. The proposed antenna operates in wideband tuning, 0.758-1.034 GHz, has a size 60 mm \(\times\) 27 mm \(\times\) 0.76 mm and operates over a wide band of sub-GHz. The miniaturization of the antenna is achieved by using the meandered structured loop slot line loaded on a varactor diode. The varactor diode was used to achieve the wideband frequency reconfigurability. The authors reported an efficiency ranging from 54-67% and total gain ranging from 0.86-1.8 dBi. [PERSON] et al. [8] presented a microstrip meandered bowtie antenna with multi-resonant and rejection bands for 5G applications. The antenna has a total size of 30 mm \(\times\) 30 mm \(\times\) 1.6 mm and was built on double-sided FR-4 substrate. The shorting via is used to connect one portion of the bowtie to the ground plane, hence enhancing the resonances. Moreover, length, width and spacing of the meander line arms are optimized to produce more resonances with an acceptable bandwidth. The proposed antenna covers S, C and X-bands, has an efficiency of 90.3%, achieved a gain of 4.46 dB and resonates at 2.7, 4.05, 5.05, 6.04, 7.15, 7.9 and 11.55 GHz. [PERSON] et al. [9] presented a compact three-port wide angular coverage patch antenna array for mmWave 5G smartphones. The proposed multi-port electrically connected patch antenna system operates at 28 GHz (Ka-band) and has a size of 24 mm \(\times\) 6.2 mm. The multiport radiator and ground plane are shared and electrically connected. To achieve the pattern diversity with angular coverage, the authors integrated the stepped impedance transformers with the corner-most elements. Moreover, the feed line is connected to a two-way non-Wilkinson-based power divider. The authors reported a wide angular coverage of 100\({}^{\circ}\), antenna efficiency of 97%, a mutual coupling less than 10 dB and a gain variation of 6 to 11 dBi across the ports. [PERSON] et al. [10] investigated and proposed a compact two antenna MIMO with a dual wideband operation for wireless and satellite applications. The antenna has a total size of 32 mm \(\times\) 20 mm \(\times\) 0.8 mm and achieves a dual wideband operation of 3.3-7.8 GHz and 8-12 GHz. The key idea was to load the monopole antenna with number of narrow slots and multiple slotted stubs to achieve multiband characteristics. Furthermore, to achieve an isolation of less than 20 dB, five concentric ring elements were etched between the two adjacent antenna elements. The proposed two antenna MIMO antenna provides a low band operation of 81.08% (3.3-7.8 GHz) and a high band operation of 40% (8-12 GHz), which makes it suitable for the Sub-6 GHz 5G new radio (NR) n77/78/79, IEEE 802.11 ac/ax, X-band/C-band wireless and satellite applications. The authors reported a gain of 3-4 dBi and a radiation efficiency of 69-80%. [PERSON] et al. [11] presented a high efficiency circular-shaped patch antenna array for Sub-6 GHz 5G applications. The proposed antenna operates at 5.57 GHz and has a total size of 160 mm \(\times\) 70 mm. The main idea was the use of transmission line and quarter wavelength transformation techniques for impedance and phase matching. To achieve the desired operating frequency band of 5.6-5.67 GHz, a circular shape of radiating element with an inner-circular slots and rectangular at its right edge is used. The four-element array configuration of the proposed antenna provides a total gain of 12.4 dB. The authors also reported an isolation between the two used ports of more than \(-\)30 dB and a total efficiency of 85.1%. [PERSON] et al. [12] proposed a planar four-port and four element smartphone flexible antenna for Sub-6 5G and WLAN smart terminals.