This study demonstrates a wideband four-element multiple input multiple output (MIMO) antenna employing a loaded metamaterial superstrate. The proposed MIMO antenna configuration has four slotted rectangular microstrip antennas arranged on a compact square substrate to attain excellent impedance matching over a wide bandwidth of 41 % (3.33 - 5.04 GHz). The suggested four-element MIMO antenna has a compact whole area of 50 × 50 × 1.6 mm ³ (0.65 λ₀ × 0.65 λ₀ × 0.002 λ₀ ), while λ ₀ is the wavelength of free space at 4 GHz. The suggested design with a novel 3×3 metamaterial superstrate structure reduces mutual coupling of no less than -23 dB among all ports. The metamaterial superstrate is positioned above MIMO elements at 15 mm (0.2 λ₀ ) for the purposes of isolation and gain enhancement. Satisfactory parameter values are also determined for the competitive MIMO performance, such as envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC). The anticipated design has been fabricated and measured. The comparison of simulation outcomes with the experimental findings is satisfactory.

The proposed work describes a corner square-cut square-patch multiple-input multiple-output (MIMO) antenna with reduced mutual coupling for circular polarization (CP). A two-port MIMO-CP antenna was designed and operated at 5.6 GHz for wireless local area network (WLAN) applications. The dimensions of the MIMO-CP antenna were $22.5\times 50{\mathrm{mm}}^2$$(0.43{\lambda }_0\times 0.933{\lambda }_0)$ and the FR4 substrate height was 1.6 mm. Between the two-elements, the edge-to-edge distance was 12.2 mm (0.227 ${\lambda }_0$), where ${\lambda }_0$ was the free space wavelength at 5.6 GHz. A slot was created in the middle of the ground in the proposed MIMO antenna to reduce mutual coupling and improve CP. The ground slot improves impedance matching and provides a better S-parameter and axial ratio (AR), according to the antenna results. According to the simulated results, the proposed antenna bandwidth of 5.23–6.42 GHz (21.4%) for S11 were <$-10$ dB, isolation was −37 dB with a peak gain of 6 dB and AR $\le 3$ dB from 5.37 to 5.72 GHz (6.25%). The proposed antennas are simple to fabricate, have low profiles, are inexpensive, have good isolation, and are CP. The diversity gain (DG) and envelop correlation coefficient (ECC) results are better in the simulated frequency band. A MIMO-CP antenna geometry prototype is built and measured for comparison, yielding good results when compared to the simulated and measured results. The MIMO-CP antenna, as designed, is suitable for WLAN applications.

This study presents a compact multi-band fork-shaped multiple input multiple output (MIMO) antenna design that integrates Carrel's log-periodic concept with the planar log-periodic array (PLPA) mechanism to improve C, Ku, K, Ka, and Q band performance. The suggested MIMO antenna full size is 54 × 44 × 1.58 mm³. The study empirically shows improved isolation and high gain of wideband MIMO antenna, addressing the requirements for modern wireless communication. The suggested self-multi-band coupling counteraction, characterized by a straightforward antenna design and extensive self-decoupling capabilities, is expected to offer considerable application value for compact and wideband MIMO systems. The observed data supports the assertion that the proposed MIMO antenna is designed to operate across a variety of frequency bands, including the C-band (4.4-5.21 GHz), Ku-band (14.30-17.64 GHz), K-band (20.10-28.10 GHz), Ka-band (28.95-30.76 GHz) and (32.38-36.42 GHz), and a segment of the Q-band (38.34-39.55 GHz). The proposed MIMO antenna's wideband performance is achieved by applying the Carrel log-periodic theory, which prescribes the geometric scaling of radiating elements. Moreover, it was found that a microstrip feed line with a diameter of 50 Ω was noteworthy in conjunction with the carrel concept. The microstrip feed line is connected to two orthogonal branches. Decoupling structures eliminate the necessity for the MIMO antenna to achieve its maximum gain of 7.21 to 9.53 dBi and exceptional element isolation of 21.54 dB. MIMO performance measurements, encompassing envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL), demonstrate favorable characteristics and field correlation performance over the operational spectrum band. The design suggested suits Ku/K-band and multi-band MIMO applications across diverse wireless systems in communication.

This paper presents a compact planar multiple input multiple output (MIMO) antenna for super wide band (SWB) applications. The presented MIMO antenna comprises two identical patches on the same substrate. Dimensions of the MIMO antenna are 0.17λ × 0.20λ × 0.006λ mm³, with respect to the lowest resonance of 1.30 GHz. The SWB antenna was manufactured using F4B substrate having a dielectric constant of 2.65 that provides a percent impedance bandwidth and bandwidth ratio of 187% and 30.76:1, respectively. The mutual coupling between the antenna elements is suppressed by placing a T-shaped corrugated strip in the mid of two antenna elements. The proposed MIMO antenna exhibits maximum diversity gain of 10 dB, low mutual coupling (<−20 dB), low envelope correlation coefficient (ECC < 0.02), efficiency >80%, and low reflection coefficient (<−10 dB) in the SWB frequency range (1.30 GH–40 GHz). The presented antenna is a good candidate for SWB applications. The designed antenna has been experimentally validated, and the simulated results were also verified.

This paper presents a four-port multiple-input multiple-output (MIMO) antenna based on frequency selective surface (FSS) for X-band communication. The suggested MIMO antenna is composed of four-slotted circular microstrip patch elements, which have been planned on an FR-4 substrate with a low profile (0.91λ0 × 0.91λ0 × 0.045λ0). The suggested antenna reduces mutual coupling (MC) and enhances gain based on the FSS technique. The band-stop FSS transmission coefficient is below -10 dB over the 7.2 to 9.1 GHz range. Additionally, for transverse magnetic (TM) and transverse electric (TE) polarization, the planned FSS offers a steady frequency response for incidence angles up to 40°. The suggested MIMO antenna bandwidth is from 7.8 GHz to 9.08 GHz (15.4%), with a peak gain of 5.2 dBi. The MC < -20 dB is attained over the entire operating bandwidth. In addition, the suggested antenna envelope correlation coefficient (ECC) is < 0.005, diversity gain (DG) is < 9.99, and channel capacity loss (CCL) < 0.3 bps/Hz is obtained in the operating frequencies band, approving good MIMO diversity performance.

This work presents a wideband, all-side square-cut square patch multiple-input, multiple-output circularly-polarized (MIMO-CP) high-isolation antenna. The MIMO-CP antenna contains a two-port square cut on all corners of the square patch, and parasitic elements of 9 × 5 periodic square metallic plates are designed and operated. The outer dimensions of the antenna are 40 × 70 mm², and the FR4 substrate height is 1.6 mm. The proposed antenna with the parasitic elements improves impedance matching and enhances S-parameters and axial ratio (AR). In the suggested MIMO-CP antenna, a parasitic element is designed and placed around the antenna periodically to reduce mutual coupling (MC) and improve CP. Simulated results show that the suggested antenna has a wide bandwidth (BW) from 4.89 to 6.85 GHz for S₁₁ and was < −10 dB with AR ≤ 3 dB from 5.42 to 6.58 GHz, with a peak gain of 6.6 dB. The suggested antennas have more than 30 dB isolation and a low profile, are affordable, easily made, and are CP. To make a comparison with the measured and simulated results, a MIMO-CP antenna structure was fabricated and tested. The suggested antenna is better in terms of efficiency, envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), and total active reflection coefficient (TARC). The proposed antenna is adequate for WLAN applications.