This article presents an innovative design for a low-profile, high-gain circularly polarized (CP) antenna using a single-layer metasurface (MTS). The proposed design incorporates an MTS layer, comprising a 4 × 4 array of hexagonal-shaped patches, printed on the top layer of the substrate. The bottom layer features a coplanar waveguide-fed slotted ground. Circular polarization and broadside radiation are achieved through the application of characteristic mode analysis (CMA). CMA is employed to simultaneously excite desired modes, aiming for wideband circular polarization and gain enhancement. Experimental results validate the effectiveness of the design, with compact dimensions of 0.67λ0 × 0.67λ0 × 0.04λ0. The measurements demonstrate an impressive impedance bandwidth of 84.3% within the 3.7–9.1 GHz. Additionally, a 3-dB axial ratio bandwidth of 18.6% is observed between 4.96 and 5.98 GHz and 3.74% between 8.38 and 8.7 GHz. The antenna exhibits excellent radiation pattern characteristics, featuring a maximum gain of 10.08 dBi at 7.1 GHz. The radiation pattern is symmetrical with broadside directionality, making the antenna well-suited for sensing applications.

A low-profile wideband circularly polarized (CP) metasurface antenna is demonstrated for C-band applications. The metasurface consists of 4 × 4 square patches with Z-shaped slots. Characteristic mode analysis is used to investigate the modal behavior of the metasurface, and a pair of degenerate modes is chosen as the operating modes. The CP radiation is realized by exciting a pair of degenerate modes of the metasurface through a slot antenna, which is used as a feed structure with a 90° phase difference. The CP bandwidth is further widened by combining the resonance modes of the metasurface and slot antenna. The measured results show that the −10 dB impedance bandwidth of the antenna is 3.47–4.76 GHz, and the 3 dB axial ratio bandwidth is 3.5–4.9 GHz with a peak gain of 6.9 dBic. Moreover, the antenna exhibits well left-hand CP radiation performances with a low profile of 0.046λ0.

In this work, a low profile ultra-wideband (UWB) antenna is designed and investigated using a novel loop-based wideband artificial magnetic conductor (WB-AMC) for gain enhancement. Initially, a compact loop antenna is designed using stub loading and further optimized for the UWB range by applying curve ground methodology. The average gain of the proposed antenna without WB-AMC is 2.7 dBi. To enhance the gain of the entire UWB range, loop-based WB-AMC in [2 × 2] forms is integrated. WB-AMC is used as a ground plane beneath the antenna. To validate the performance, the UWB antenna and WB-AMC are fabricated and tested. The measured results confirm the entire UWB range. Proposed antenna provides a peak gain of 9.4 dBi and an average gain of 5.8 dBi. Vertical profile reduction of 50% is achieved compared to perfect electric conductor ground. The proposed UWB antenna is a potential candidate for UWB wireless applications due to its attractive features such as low profile, wide bandwidth coverage, omnidirectional pattern, constant high gain, and group delay.

A low-profile, wideband dual-polarized 1 × 2 multiple-input-multiple-output (MIMO) antenna with frequency selective surface (FSS) decoupling technique is presented. Low profile is realized with two different artificial magnetic conductor (AMC) cells out of which one operates at 3.5 GHz and other with dual band at 3.1 and 4.5 GHz. The proposed antenna height is maintained at 0.125λ0 which is significantly reduced when compared with the conventional perfect electric conductor (PEC) ground plane. Wideband dual polarization is enabled by two pairs of bow-tie antenna elements surrounded by a square ring placed in the orthogonal orientation. To mitigate the near-field coupling in 1 × 2 MIMO an FSS wall is constructed with wide band stop characteristics from 2.85 to 4.75 GHz. Measured results show by inserting FSS wall vertically, coupling reduction is improved by 27 dB over the existing coupling and the antenna exhibits a bandwidth of 57.14% (2.95–4.95 GHz) for VSWR<2 with port isolation of more than 25 dB for entire band of operation.

A novel dual-band planar antenna with a low profile for mobile communication system is proposed in this paper. The antenna is composed of one shorted patch with two radiating notches for low frequency resonance and one square patch for high frequency resonance. The low profile is achieved via the shorting patch, which introduces the parallel electrical field between the reflector and antenna. A step-impedance microstrip line is used to feed the antenna. The coupling between the square patch and microstrip line cancels out the inductance of shorting probe, which increases the working bandwidth of proposed antenna. A prototype with a low profile of 0.0286λ is fabricated and measured. The antenna achieves dual impedance bandwidths of 1.6% for the low frequency band and 60% for the high frequency band, covering the frequency range 851–865 MHz and 1.97–3.65 GHz, respectively. The measured results show good agreements with the simulated ones.