# Antenna Designs for 5G/IoT and Space Applications, 2 nd Edition
## 2 Short Presentation of the Papers
[PERSON] et al. [6] proposed a compact, multi-band, circularly polarized, shared-aperture antenna for CubeSat applications at S-band (2013-2043 MHz) and X-band (8320-8530 MHz). The design integrates an S-band slot antenna with an X-band square patch antenna in one signal antenna design to provide uplink/downlink communication links. The antenna has circular polarization and achieves high gains of 7.7 dBic and 12.8 dBic at S-band and X-band, respectively. The use of a partial reflective surface (PRS) dielectric layer enhances the antenna performance. The S-band patch serves as a Telemetry, Tracking, and Command (TT&C) antenna, while the X-band patch supports high-speed data downlink, making it suitable for deep space CubeSat missions. The shared-aperture approach offers an efficient, space-saving solution for future CubeSat communications. [PERSON] et al. [7] presented a drone-based wireless network system for post-disaster communication, focusing on mitigating cross-link interference in local 5G networks. The numerical analyses presented by the authors show that using circular polarization significantly improves the Signal-to-Interference Ratio (SIR). In a scenario with only access links, circularly polarized antennas improve the SIR from less than 20 dB to over 40 dB. Similarly, in cases involving backhaul links, the proposed antenna system achieves an SIR of 16.8 dB, which was challenging with conventional linear polarization. The proposed system operates at 28 GHz with 100 MHz bandwidth and is suited for rapid deployment in disaster-affected areas. [PERSON] et al. [8] proposed a high gain 4 \(\times\) 1 microstrip patch array antenna for 24 GHz radar applications. The main idea is to add two metallic plates along the array axis, resulting in enhanced gain. After appending metallic plates, the gain of the proposed antenna design increased from 9.8 dBi to 16.8 dBi. The gain was maximized with a tilting angle of 70\({}^{\circ}\) and a metallic plate length of 50 mm. The method demonstrated significant enhancements in gain, radiation patterns, and input reflection coefficient. This approach can be applied to radar, satellite communications, and future 5G/6G systems. [PERSON] et al. [9] presented an eight-element MIMO antenna system for 5G mobile phones, designed with a modified E-slot on the ground to enhance isolation. The key idea of using the E-slot is to reduce the coupling between antenna elements by suppressing the ground current effects, achieving isolation greater than \(-\)21 dB in the 3.5 GHz band. The proposed system operates in the 3.4-3.65 GHz frequency range and achieves a \(-\)6 dB impedance bandwidth of 250 MHz. The system exhibits an envelope correlation coefficient (ECC) of \(<\)0.01 and an ergodic channel capacity of 43.5 bps/Hz, indicating excellent performance for 5G MIMO applications. [PERSON] et al. [10] introduced a graphene plasmonic MIMO microstrip patch antenna designed for THz wireless communication operating at a 1.9 THz resonance frequency. The authors used E-shaped metamaterial (MTM) unit cells to enhance isolation from \(-\)35 dB to \(-\)54 dB and employed graphene-based reconfigurable intelligent surfaces (G-RIS) placed above the patches for beam steering in directions of \(\pm\)60\({}^{\circ}\). Moreover, they placed a graphene artificial magnetic conductor (G-AMC) layer underneath the antenna to further improve the gain from 4.5 dBi to 10 dBi. They claimed that their proposed antenna is suitable for IoT applications, providing high gain, data rates, and beam-steering capabilities for smart homes and radar applications that require wide scanning angles and high-speed communication. [PERSON] et al. [11] proposed an eight-element phased array antenna for 5G hand-portable devices, particularly smartphones. The antenna uses air-filled, slot-loop, metal-ring elements arranged in a 1 \(\times\) 8 linear configuration along the edge of the smartphone mainboard, covering the 21-23.5 GHz sub-mm-wave 5G bands.