A compact S-shaped 2×1 MIMO antenna for WLAN/WiMAX applications

In this paper, we propose a compact Multiple Input Multiple Output (MIMO) antenna system with high isolation for wireless applications in 5G connected devices. This MIMO antenna system with the size of 92 × 88 mm2 consists of two elliptical antennas symmetrically arranged next to each other. Two decoupling methods which are neutralization and Defected Ground Structure (DGS) are applied to ensure diversity of the proposed MIMO antenna. The single and MIMO antennas are simulated and analyzed then fabricated and measured. A good agreement between measurements and simulations is obtained. These configurations, dedicated to covering the 3.4 GHz band ‐3.8 GHz, have shown very satisfactory performances more than ‐30 dB in terms of reduction of mutual coupling between the antennas constituting our system. MIMO diversity parameters, such as Envelope Correlation (ECC), Diversity Gain (DG), and total efficiency, are also studied for each proposed MIMO system. Thus, results demonstrate that our two proposed antenna configurations are very suitable for 5G MIMO applications.

This paper presents the design and implementation of a novel four‐port multiple input multiple output (MIMO) antenna with reconfigurable filtering characteristics. The proposed filtering MIMO antenna is constructed using a super wideband (SWB) monopole. The feedline of the monopole radiator is integrated with a microstrip filter network. Reconfigurable filtering characteristics are realized using a feed selection network making the antenna work at two modes viz. SWB mode (2.2 to over 20 GHz) and dual narrow‐band (d‐NB) mode (2.45 and 5.8 GHz). The feed selection is accomplished using a PIN diode. An interlocked four‐port MIMO antenna is then constructed using the proposed reconfigurable filtering monopole antenna. The proposed antenna exhibits an average gain greater than 5.2 dBi in both operating modes and has total efficiency greater than 80%. The MIMO parameters such as envelope correlation coefficient (ECC), diversity gain (DG), and mean effective gain (MEG) are evaluated and presented. The prototype MIMO antenna is fabricated and the experimental results are validated in real‐time. The proposed reconfigurable MIMO antenna is suitable for wireless local area network (WLAN), Internet of things (IoT), dedicated short‐range communication (DSRC), ultra‐wideband (UWB), and SWB applications in the automotive scenario.

Compact circularly polarized 2 and 4 port multiple input multiple output antennas with bandstop filter isolation technique

This paper presents the design and simulation of a compact multiple-input multiple-output (MIMO) antenna structure optimized for operation within the 2.4 GHz frequency band, which is widely utilized in wireless applications such as Wi-Fi, Bluetooth, and various Internet of Things (IoT) devices. The proposed MIMO antenna features a novel configuration, incorporating a modified rectangular patch on a cost-effective FR-4 substrate. To improve isolation between the two antenna elements within the operating band, orthogonal polarization is employed, effectively minimizing mutual coupling and enhancing overall MIMO performance. Simulation results demonstrate excellent impedance matching at the target frequency, with a return loss S₁₁ of –26 dB around 2.4 GHz, indicating minimal reflection and efficient power transfer. The antenna exhibits stable performance across the 2–3 GHz range, with a distinct resonance peak confirming its narrowband characteristics. The envelope correlation coefficient (ECC) is very close to zero, indicating low signal correlation between the elements and resulting in high diversity gain (DG) at the operating frequency. These results highlight the suitability of the proposed MIMO antenna for integration into modern embedded and portable wireless communication systems.

This paper presents a new design of a compact dual-band Multiple Input Multiple Output (MIMO) antenna with high isolation for WLAN and X-band satellite applications. The proposed antenna is realized using three slots: the first slot is used on the upper layer to create the second resonance frequency at 5.3 GHz and two symmetrical slots are etched on the bottom layer to enhance the impedance bandwidth of the two operating bands. In order to obtain a low mutual coupling, the two antenna elements have an orthogonal polarization. The simulated results show that the MIMO antenna has a high isolation (S21 ≤−22.5 dB) at the two desired bands with impedance bandwidths are about 4.15% (5.19–5.41 GHz) and 4.81% (7.30–7.66 GHz). In addition, the MIMO parameters like envelope correlation coefficient (ECC), diversity gain (DG), Total Active Reflection Coefficient (TARC), realized gain and efficiency are also analyzed.

In this paper, LTE band 40 (2300-2400MHz) Multiple input Multiple output (MIMO) Antenna array is proposed. MIMO antenna array consist of two diagonally placed angular ring slot antenna cut from two edges of ground plane. MIMO antenna array has a volume 60 × 60 × 1.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . Two antenna elements are placed orthogonal to each other and stubs are arranged to improve isolation between two antenna and envelope correlation coefficient characteristics. Channel capacity of proposed MIMO antenna is calculated based only on S-parameters. Performance of MIMO antenna in terms of S-parameter, envelope correlation coefficient (ECC), radiation pattern, capacity loss, channel capacity, TARC is simulated. The results shown that MIMO antenna array is good candidate for 100MHz bandwidth LTE band.

A broadband and compact size circularly polarized (CP) two-port multiple input multiple output (MIMO) antenna with a footprint of 25 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times20$ </tex-math></inline-formula> mm is investigated. The designed oval-shaped MIMO antenna employs concentric rings with oval slots (CROS), along with a circular radiator and two open-ended parallel protruded stubs. The CP radiation is achieved by embedding three oval slots, in which two of them are deployed at the left and right side of the concentric rings, whereas the third one is deployed at the top section of the concentric rings. The measured 10-dB impedance bandwidth of the proposed MIMO antenna was 46.30% (3.12–5.00 GHz), and its corresponding 3-dB axial ratio bandwidth (ARBW) was 41.34% (3.30–5.02 GHz). Furthermore, very wide beamwidths of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$137^{\circ }\pm 0.2$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$154^{\circ }\pm 0.2$ </tex-math></inline-formula> were measured in the right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) radiation patterns, respectively. The minimum achieved isolation between the antenna elements is 18.50 dB without using any additional decoupling structure, and the calculated envelope correlation coefficient (ECC) < 0.03.

This paper presents the design of a novel ultra-wideband (UWB) Multiple Input Multiple Output (MIMO) antenna with triple-band notches. In the proposed design, two antenna elements are positioned within a 38 × 29 mm2 area, using a common ground plane. I-, C-, and U-shaped slots are incorporated to reject frequencies in the WiMAX, WLAN, and X bands, respectively. Good isolation between the radiator elements is achieved through the implementation of the Defective Ground Structures (DGS) technique and the addition of L-stubs to the ground plane. The proposed MIMO antenna exhibits low isolation, below −20 dB, across its operating band. Moreover, the envelope correlation coefficient (ECC) and diversity gain (DG) values of the designed antenna are less than 0.025 and greater than 9.98 dB, respectively. The scattering parameters and radiation characteristics of the proposed MIMO antenna were tested through a fabricated prototype. The MIMO antenna shows promise for UWB applications due to its compact structure and notch-band features.

This paper investigates a small size 2 × 2 wideband multiple input multiple output (MIMO) antenna covering frequency band of 2.61 to 5.52 GHz. The antenna structure consists of elliptical ring patch with multiple circumferential slots. The edge-to-edge separation between the patches are kept 3.6 mm with volumetric dimensions of 30 × 46 × 1.6 mm3. The narrow slits are etched in the tapered ground plane to obtain the wideband characteristics. The electromagnetic coupling is improved more than 16 dB by employing the neutralization technique. The measured average gain and radiation efficiency of the proposed antenna are above 2.61dBi and 83.54%, respectively across the operating band. In addition to that, the important MIMO diversity parameters are investigated. The group delay and signal analysis in different orientations are also studied to ensure the quality performance of the antenna. The proposed MIMO antenna is simulated using CST microwave studio and further validated with the measurements. In addition to that, the parallel and orthogonal configuration of 4 × 4 MIMO antennas are analyzed by extending the proposed 2 × 2 MIMO design. The 4-port MIMO antennas exhibit the operating frequency bands varying from 2.80 to 5.58 GHz and 3.4 to 5.52 GHz, respectively for parallel and orthogonal MIMO configurations. The diversity parameters of 4-port MIMO antennas are calculated and compared with the measured results to verify its practical applications. Finaly, the SAR analysis of the antenna is presented at 3.08 and 5.20 GHz for 1/10 g tissues and are found 0.111/0.106 and 0.079/0.063 W K−1g−1, respectively. The proposed MIMO antenna designs are suitable for modern high-speed communication for 5G and sub-6 GHz frequency bands.

Multiple Input Multiple Output (MIMO) antenna technology plays a crucial role in enhancing the performance of modern wireless communication systems. This survey explores the latest advancements in MIMO antenna design and focuses on innovations that improve performance metrics such as isolation, bandwidth, gain, and efficiency. The paper reviews various antennas: wideband, compact, tri-polarised, ultra-wideband (UWB), super-wideband (SWB), and multi-band antennas. It highlights significant advancements in antenna design, such as developing novel feeding structures, using Characteristic Mode Analysis (CMA) to optimise performance, and integrating Electromagnetic Band Gap (EBG) structures for improved isolation. Decoupling techniques are also discussed to minimise mutual coupling between elements. The evolution of SWB-MIMO antennas has been key in achieving high isolation, wide bandwidths, and low envelope correlation coefficients (ECC), essential for applications such as 5 G, IoT, and UWB systems. This paper consolidates a broad spectrum of research on MIMO antenna technologies and presents emerging trends aimed at improving system efficiency and reducing interference. Key innovations discussed include fractal designs, multi-band functionality, and flexible antenna materials, representing the forefront of MIMO antenna development for future communication systems.

In this article, a compact 4-port UWB (Ultra-Wide Band) MIMO (Multiple Input Multiple Output) antenna is proposed. A low profile FR-4 substrate is used as a dielectric material with the dimensions of 58 × 58 mm2 (0.52λ × 0.52λ) at 2.8 GHz and a standard thickness of 1.6 mm. The proposed design characterizes an impedance bandwidth starting from 2.8 to 12.1 GHz (124.1%). Each of the four elements of the proposed MIMO antenna configuration consists of a monopole antenna with PG (partial ground) that has a slot at its center. The corner of each patch (radiator) and ground slot are rounded for impedance matching. Each unit cell is in an orthogonal orientation, forming a quad-port MIMO antenna system. For reference, the partial ground of each unit cell is connected meticulously with the others. The simulated results of the proposed quad-port MIMO antenna design were configured and validated by fabrication and testing. The proposed Quad-port MIMO design has a 6.57 dBi peak gain and 97% radiation efficiency. The proposed design has good isolation below 15 dB in the lower frequency range and below 20 dB in the higher frequency range. The design has a measured ECC (Envelop Correlation Co-efficient) of 0.03 and DG (Diversity Gain) of 10 dB. The value of TARC (Total Active Reflection Coefficient) over the entire operating band is less than 10 dB. Moreover, the design maintained CCL (Channel Capacity Loss) < 0.4 bits/sec/Hz and MEG (Mean Effective Gain) < 3 dB. Based on the obtained results, the proposed design is suitable for the intended high data rate UWB wireless communication portable devices.

A compact multiband pattern diversity antenna for Multiple input multiple output (MIMO) applications is being proposed. The pattern diversity antenna is designed for 2.6 GHz LTE, 3.5/5.5 GHz WiMax, 3.3 GHz MIMO and 5.2 GHz WLAN applications for mobile devices. The compact size of the MIMO antenna (41.05 × 21.1 mm) is due to having compact individual monopole antennas each of dimension 17.5 × 10 mm. A T-shaped and inverted L-shaped stub in the ground plane reduces mutual coupling due to near field whereas slots introduced in the ground plane prevents current to flow through the common ground plane. The important characteristics of MIMO antenna like diversity gain and envelope correlation coefficient have also been presented. Measured and simulated radiation patterns presented show that the MIMO antenna proposed provide pattern diversity.

A small-sized, circular-shaped Multiple Input Multiple Output (MIMO) antenna is investigated in this study. This antenna is suitable for wireless applications at 2.4 GHz and 5 GHz. The MIMO antenna comprises two identical, back-to-back slotted circular patch antennas with a common ground plane. The radiation direction of each antenna is oriented at 180° relative to its counterpart, providing good isolation between them. The novelty of this two-port MIMO antenna lies in its compact size of only 0.001λ0³ (where λ0 corresponds to the free space wavelength at 2.4 GHz) along with its dual-band operating capability. Important parameter values of this MIMO antenna are analyzed using electromagnetic analysis software. Directivity values of 5.5 dBi (at 2.4 GHz) and 6.7 dBi (at 5 GHz), as well as reasonable bandwidths of 50 MHz (at 2.4 GHz) and 160 MHz (at 5 GHz), are obtained for this antenna. Envelope Correlation Coefficients (ECC) of 0.01 at 2.4 GHz and 0.003 at 5 GHz, along with a nearly 10 dB Diversity Gain (DG), are achieved at both frequencies for this compact antenna system. The ratio of Mean Effective Gain (MEG) between the two antennas is found to be 0.02 dB at 2.4 GHz and 0.05 dB at 5 GHz. Channel Capacity Loss (CCL) values of 0.16 bits/s/Hz and 0.089 bits/s/Hz are obtained at 2.4 GHz and 5 GHz, respectively. The characteristic parameters of this two-port circular patch antenna system are compared with those of similar antennas reported in recent literature.

A tri-band antenna, which consists of a compact conventional phone antenna and a wideband multiple-input multiple-output (MIMO) antenna, is presented for mobile phone application. Three slits etched into the ground plane are used to reduce the mutual coupling between the conventional phone antenna and the MIMO antenna, moreover, this slits are help to relieve the impedance matching degradation of the conventional phone antenna caused by the mutual coupling. A wideband T-shaped neutralization line without effect on the performance of the conventional phone antenna is applied to improve the isolation for the MIMO antenna, and high isolation is achieved within the wide operation band. For the convention phone antenna, the two operation bands with VSWR ≤ 3 are 0.89–0.96 GHz and 1.71–2.18 GHz, respectively, and nearly omnidirectional radiation patterns in H-plane are achieved. The operation band of the MIMO antenna with VSWR ≤ 1.7 and isolation ≥ 20 dB is 2.4–3.7 GHz, and the two MIMO antenna elements have back-radiation patterns for achieving diversity gain. The simulated and the measured results are in a good agreement.

The excessive use of digital platforms with rapidly increasing users in the wireless domain enforces communication systems to provide information with high data rates, high reliability and strong transmission connection quality. Wireless systems with single antenna elements are not able to accomplish the desired needs. Therefore, multiple-input multiple-output (MIMO) antennas are getting more attention in modern high-speed communication systems and play an essential part in the current generation of wireless technology. However, along with their ability to significantly increase channel capacity, it is a challenge to achieve an optimal isolation in a compact size for fifth-generation (5G) terminals. Portable devices, automobiles, handheld gadgets, smart phones, wireless sensors, radio frequency identification and other applications use MIMO antenna systems. In this review paper, the fundamentals of MIMO antennas, the performance parameters of MIMO antennas, and different design approaches and methodologies are discussed to realize the three most commonly used MIMO antennas, i.e., ultra-wideband (UWB), dual-band and circularly polarized antennas. The recent MIMO antenna design approaches with UWB, dual band and circularly polarized characteristics are compared in terms of their isolation techniques, gain, efficiency, envelope correlation coefficient (ECC) and channel capacity loss (CCL). This paper is very helpful to design suitable MIMO antennas applicable in UWB systems, satellite communication systems, GSM, Bluetooth, WiMAX, WLAN and many more. The issues with MIMO antenna systems in the indoor environment along with possible solutions to improve their performance are discussed. The paper also focuses on the applications of MIMO characteristics for future sixth-generation (6G) technology.