The design of a metasurface with low radar cross section (RCS) property is presented in this paper. The low scattering of the metasurface is achieved by applying the artificial magnetic conductor (AMC) unit cells in three different configurations. Two different AMC unit cells with an effective phase difference of 180 ± 37° are first designed to analyze the out of phase reflection in a wideband frequency range from 5.9 to 12.2 GHz. Then, the unit cells are placed in a chessboard-like configuration, newly constructed rotated rectangular-shaped configuration, and optimized configuration to study and compare the RCS reduction performance. All designs of the metasurface with different configurations show obvious RCS reduction as compared with the metallic plate of the same size. However, the relative bandwidth of the optimized metasurface is larger than the chessboard-like configuration and rotated rectangular-shaped configuration. To certify the results of the simulations, the metasurface with the optimized configuration is fabricated further to measure the RCS reduction bandwidth. The measured results are in good accordance with the simulated results. Therefore, the proposed metasurface can be a good option for applications where low RCS is desirable.

This study proposes a compact, low-profile, four-port dual-band monopole multiple-input-multiple-output (MIMO) antenna array for unmanned aerial vehicle (UAV) communication systems. Each monopole antenna of the array features a modified T-shaped radiator configuration and is printed on a Rogers RT5880 substrate with compact dimensions of 134.96 mm × 134.96 mm × 0.8 mm. A four-element square MIMO configuration with sequential 0°, 90°, 180°, and 270° rotations was integrated smoothly into the UAV body. A prototype of the MIMO array was fabricated and experimentally evaluated, with measured results showing a close correlation to simulated results. The proposed dual-band monopole antenna demonstrated one of the widest impedance bandwidths of 46.15% at 2.4 GHz (2.04 to 3.25 GHz) IEEE 802.11b and 31.85% at 5.8 GHz (5.37 to 7.38 GHz) IEEE 802.11a on a thin 0.0064 λ_o substrate while achieving high transmission efficiency. The isolation of the proposed four-port MIMO design was measured at 23 dB at 2.4 GHz and 19 dB at 5.8 GHz. The MIMO array’s total efficiency of each monopole antenna was measured at 96% at 2.4 GHz and 89% at 5.8 GHz. The design has measured diversity parameters such as an ECC below 0.01 and a DG of approximately 10. Based on these results, the proposed design suits the UAV communication system.

This study presents a four-port sequentially rotated circular polarized (SRCP) low-profile antenna array with enhanced isolation through a dual-layer, double-sided metasurface-based decoupling (DSMD) structure for 5G communications. The dual-layer DSMD structure is placed over the SRCP antenna array. The DSDM, with positive permeability and epsilon-negative properties, improves the isolation in an SRCP antenna array by manipulating electromagnetic wave behavior. Its band-stop characteristics attenuate 3.5 GHz within the CP antenna's bandwidth, minimizing interference between closely spaced CP antennas. The dual-layer DSDM has achieved a polarization conversation ratio (PCR) of 92% at 3.5 GHz and 90% at 3.1 to 3.7 GHz. To validate our simulation results, a prototype of the SRCP antenna array with dimensions 0.92λ_o× 0.92λ_o× 0.0281λ_o at 3.5 GHz is fabricated, along with the proposed decoupling DSMD with dimensions of 1.03λ_o× 1.03λ_o× 0.0409λ_o at 3.5 GHz. The measurements show that integrating a DSMD substantially enhances inter-port isolation, realized gain, and efficiency. The measured isolation between the SRCP antenna array elements is increased by over 25 dB across the frequency band of 3.3 GHz to 3.7 GHz. At the 3.5 GHz, the measured isolation reaches 27 dB. Additionally, a 3 dB axial ratio and envelope correlation coefficient <0.0004 are achieved across the operating band, with a peak realized gain of 8.20 dBic and 76% total efficiency obtained at 3.5 GHz. The CP antenna generates a broadside radiation pattern at 45° and 135° in the azimuth plane. These advancements position it as a promising solution for 5G communication applications.

In this paper, a novel design of a dual-band planner Inverted- F antenna (PIFA) is proposed for the application of Long term evaluation (LTE) and wireless local area network (WLAN). By feeding a single PIFA with two feeding ports that are placed perpendicular to each other, polarization diversity is obtained in this design. Two slots are introduced on the top patch of the PIFA for dual-band operating, and DGS (defected ground structure) is used to achieve high isolation. The proposed antenna can cover the frequency bandwidth from 2.29 GHz to 3.79 GHz and from 4.95 GHz to 6.99 GHz, with port mutual coupling lower than -10.2 dB. The proposed PIFA is a suitable candidate for WLAN and LTE communications due to its compact size and low cost.