A wideband polarization diversified MIMO antenna with improved isolation using machine learning optimized metasurface absorber

SummaryA small size neutralization line integrated flower‐shaped MIMO antenna is designed and analyzed for sub‐6 GHz type 5G NR frequency bands like n79 (4400–5000 MHz), n78 (3300–3800 MHz), n77 (3300–4200 MHz), and WLAN (5150–5825 MHz) applications. The novel approach of theory of characteristic mode analysis (TCMA) is introduced to provide physical insight of the designed structure and its characteristics behavior. Due to the suggested modifications in the geometry, the isolation among the patches is greatly increased. The overall miniaturized dimension of the MIMO antenna is 25 × 40 mm2. The edge‐edge spacing among the elements is 0.0233λ. The prototype antenna is fabricated and measured that shows good agreement compared with simulated results. The designed MIMO antenna without the presence of decoupling structure offers an isolation of 28 dB, gain of 3.6 dBi, and radiation efficiency of 69.7% at the resonant frequency. The proposed MIMO antenna covers a broad range of frequency band from 3.296 to 5.962 GHz with −10 dB impedance bandwidth of 2666 MHz and maintains a good isolation of greater than 50 dB for the entire operating band. The tested radiation efficiency and gain are 85.3% and 6.22 dBi at 3.5 GHz. Moreover, the diversity parameters of the neutralization line integrated MIMO antenna, that is, channel capacity loss (CCL) isolation, mean effective gain (MEG), total active reflection coefficient (TARC) diversity gain (DG), and envelope correlation coefficient (ECC), are analyzed and discussed in this article.

A novel approach for low mutual coupling and ultra-compact Two Port MIMO antenna development for UWB wireless application

In this manuscript, a compact circularly polarized MIMO antenna with 100% 3-dB axial ratio attributes has been conceived for 5G NR Sub-6 GHz frequency bands. The simulated and measured findings indicate that the suggested antenna has an impedance bandwidth (−10 dB) in the range of 2.88–3.88 GHz; nonetheless, the measurements show a range of 3.0–4.4 GHz, with a 3-dB Axial ratio Bandwidth (ARBW) in the area of 2.73–5.42 GHz (Simulated) and 2.75–5.45 GHz (Measured), respectively. With left-handed circular polarization (Port-1 and Port-2) and right-handed circular polarization (Port-3 and Port-4), the antenna spans the proposed 5G band spanning N77 (3.3 to 4.2 GHz) and N78 (3.3 to 3.8 GHz). The suggested MIMO antenna design consists of a singular structure including an L-shaped radiating element and a rectangular ring-shaped ground plane, both co-planar. A compact MIMO module with two ports is constructed by reflecting the L-Shape radiator across the x-axis, while a MIMO module with four ports can be generated by reflecting the two-port antenna image across the y-axis. The functionality of the proposed module as an antenna have been validated by simulation, including the calculation and analysis of various antenna and diversity characteristics. The modelling results are then corroborated by the measurement outcomes of the constructed antenna. The suggested design is deemed suitable for use as a MIMO antenna due to its optimum value of envelope correlation coefficient (ECC), diversity gain (DG), channel capacity Loss (CCL), total active reflection coefficient (TARC), mean effective gain (MEG) and its isolation between the antenna components, which exceeds 18 dB. The suggested design demonstrates a high degree of concordance between the simulated and measured outcomes.

The design, fabrication, and performance evaluation of a compact, high-isolation two-port MIMO antenna for the 2.4 GHz ISM band are presented in this paper. Constructed on a cost-effective FR-4 substrate, the antenna employs orthogonal polarization diversity and modified rectangular patches to minimize mutual coupling between the two ports. Stepped impedance feed lines and a partial ground plane are incorporated to enhance impedance matching and radiation characteristics. Simulated and measured results demonstrate close agreement, with a return loss (S11) of approximately -30 dB and inter-port isolation (S21) exceeding - 22 dB at 2.4 GHz. The MIMO antenna achieves a stable peak gain of 2.75 dBi and radiation efficiency above 85%. Key diversity metrics include an envelope correlation coefficient (ECC) below 0.0004, a diversity gain (DG) greater than 9.99 dB, a channel capacity loss (CCL) below 0.012 bits/s/Hz, a total active reflection coefficient (TARC) below -26 dB, and a mean effective gain (MEG) of approximately -3.0 dB. These characteristics, combined with the antenna's compact size, render it highly suitable for integration into modern IoT devices and compact wireless communication systems.

This paper presents a compact, uni-planer wide band Multiple-Input-Multiple-Output (MIMO) antenna. The designed antenna array has a compact size of (26mm x 31mm) covering a wide frequency band from 3.1GHz - 11GHz. A partial ground plane shared by two radiating patches is used. A ground stub and a single column Electromagnetic Bandgap (EBG) structure in between the two radiating patches results in very low mutual coupling in the designed antenna. The proposed MIMO-antenna was evaluated through different performance metric indicators like channel capacity loss, far-field radiation pattern, S-parameters, envelope correlation coefficient, peak gain, diversity-gain and radiation efficiency. Our designed MIMO antenna has a very high isolation amongst the MIMO antennas ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{S}_{21} &lt; -25$ </tex-math></inline-formula> dB), a high Diversity-Gain (DG <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;9.995$ </tex-math></inline-formula> dB), a very low Envelope Co-relation Coefficient of (ECC < 0.001) and low Channel-Capacity-Loss (CCL < 0.1bits/s/Hz). The said antenna has an average radiation efficiency of 85.5% and a peak gain of (5.67dB) within the ultra-wideband (UWB) spectrum. A 0.8mm thick FR-4 substrate is used to fabricate the MIMO-antenna and tested in an anechoic chamber. The measured results closely match with the simulated results.

In this article, a novel metasurface absorber is designed for RCS reduction as well as high isolation in a 4-elements MIMO antenna. A unit cell of metasurface absorber is amalgamated by concentric circular and elliptical-shaped rings with four 300 ohms lumped resistances. Absorbance at the intended frequency band (i.e. 8.75 GHz-9.00 GHz) of metasurface absorber is more than 90.0% and its reflectivity is tending to zero. Therefore, the isolation between antennas due to this absorbance is improved by 12 dB, and the total isolation of the antenna is achieved less than 23 dB. Similarly, the Radar cross-section (RCS) of the antenna is also significantly reduced by 10dBm2. This MIMO antenna with an absorbing structure is fabricated on a richly existing FR4 substrate with dimensions of 55 × 40 × 1 mm3. The performance of the designed MIMO antenna is also judged by diversity parameters similar to Envelope correlation coefficient (ECC), Directive gain (DG), Mean effective gain (MEG), Channel capacity loss (CCL), Total Active Reflection Coefficient (TARC), and channel capacity, etc. for the proposed frequency band. The simulated and measured ECC of the proposed MIMO is less than 0.073 which exhibits that this antenna is suitable for military application in radiolocation and navigation.

SummaryCurrent generation of mobile and wireless communication can have portable, compact, lightweight, highly reliable, easy to access, high coverage, high capacity, high SNR, and high gain antennas for non‐line‐of‐sight communication. MIMO technology provides these all and has data rate optimization, diversity, spatial multiplexing, and solution of multipath propagation. The current requirement for designing a compact MIMO antenna with better isolation is what spurred the creation of the proposed antenna. In this research, a mathematically inspired generalized antenna is proposed for 1.8/1.9 GHz application in the 1.5–2.1 GHz range. The bandwidth in this case is 600 MHz. The return loss is −78 dB at the resonant with more than 17 dB isolation in the entire band. The envelope correlation coefficient (ECC) is found below 5 × 10−3. The overall size of the antenna is 40 × 81.76 mm2on FR‐4 dielectric laminate. To improve the isolation further, a parasitic element is used between the radiating elements, and it provides 7 dB improvements in isolation and is confirmed by the surface current distribution. The radiation efficiency is more than 90%, and maximum current density of 29.9 A/m2 is found in the entire band. In this study, evaluation and discussion of additional antenna performance parameters channel capacity loss (CCL), mean effective gain (MEG), and specific absorption rate (SAR) are also included.

This article introduces a compact (32 × 64 × 0.8 mm3) four port MIMO antenna for K-band for satellite and for band 5G NR- n257, n258 &amp; n261 for mmWave applications. The proposed antenna is designed at 24 GHz and selected an optimal design (Stage 3) after successive analysis of different stages (Stage 1, Stage 2 &amp; Stage 3) performance. The radiating plane consists of an inverted L-shaped geometry, whereas the ground plane has a rectangular annular ring geometry. The proposed antenna offers an extremely large bandwidth of 20.02–30.8 GHz (simulated) &amp; 20.2–30.3 GHz (measured) and an excellent isolation of greater than 25 dB in entire band. The suggested four-port MIMO antenna system obtained a significant peak gain of 9.5 dB at 24 GHz frequency. MIMO performance metrics in terms of ECC (envelope correlation coefficient), DG (diversity gain), TARC (channel capacity loss), CCL (channel capacity loss) and MEG (mean effective gain) of the proposed antenna is also studied and found in acceptable limits; ECC (0.00003), DG (9.87 dB), TARC (&lt; −10 dB) CCL (&lt; 0.4 bps Hz−1 s−1) and MEG ((−12 dB &lt; MEG &lt; −3 dB). Simulated results of the proposed antenna are validated with experimental results and found in close proximity. The performance of the proposed antenna makes it suitable for satellite and 5G and 5G advanced applications.

The work proposes a low-profile, wideband circularly polarized (CP) dual-element Multiple-Input-Multiple-Output (MIMO) antenna design for C-band and selected 3GPP FR1 5G NR bands. The designed two-element MIMO antenna utilizes a planar patch configuration and achieves high isolation by strategically incorporating an optimized rectangular-shaped slot in the ground plane of the antenna, which acts as a decoupling structure, eliminating the need for any external complex structure. The two MIMO elements are placed with an optimized decoupling slot of 7 mm width to reduce mutual coupling between them. The performance of the proposed CP-MIMO antenna has been validated comprehensively through both full-wave simulations and experimental measurements. The antenna demonstrates a measured −10 dB impedance bandwidth of 3.81 GHz (4.24–8.05 GHz) and a 3-dB axial ratio bandwidth (ARBW) of 2.7 GHz (4.36–7.06 GHz), validating CP performance. The key MIMO parameters investigated include Total Active Reflection Coefficient (TARC &lt; −10 dB), Envelope Correlation Coefficient (ECC &lt; 0.005), Diversity Gain (DG ≈ 9.98), and Channel Capacity Loss (CCL ≈ 0.35 bits s −1 Hz −1 ), confirming its excellent diversity standards. The proposed CP MIMO antenna occupies a compact footprint of 49 × 24 × 1.6 mm 3 , with better inter-element isolation of more than 20 dB across most of the operating band, a peak gain of 5.7 dB, high simulated efficiency of 96%, and polarization agility. Furthermore, the scalability of the design has been comprehensively demonstrated by extending it to 3-port and 4-port MIMO configurations, supported by detailed simulation results. These results validate its suitability for integration into next-generation wireless communication systems.

A tree-shaped graphene-based microstrip multiple-input and multiple-output (MIMO) antenna for terahertz applications is proposed. The proposed MIMO antenna is designed on a 600 × 300 μm2 polyimide substrate. The designed MIMO antenna provides a wide impedance bandwidth of 88.14% (0.276–0.711 THz) due to the suggested modifications in the antenna configuration. The MIMO design parameters like total active reflection coefficient (TARC), mean effective gain (MEG), envelope correlation coefficient (ECC) and diversity gain (DG), channel capacity loss (CCL) are evaluated, and their values are found within acceptable limits. The proposed MIMO structure offers MEG ≤ − 3.0 dB, TARC ≤ − 10.0 dB, DG ≈ 10 dB, CCL < 0.5 bps/Hz/s and ECC < 0.01 at the resonant frequency. At the resonant frequency, the isolation between the radiating elements of the proposed MIMO antenna is recorded as − 52 dB. The variations in operating frequency and S-parameters are also analyzed as a function of the chemical potential (μc) of the graphene material. The parametric analysis, structural design evolution steps, surface current distribution, antenna characteristics parameters and diversity parameters are discussed in detail in this paper. The designed MIMO antenna is suitable for high-speed short-distance communication, video-rate imaging, biomedical imaging, sensing and security scanning in the THz frequency band.

This article demonstrates a compact wideband four-port multiple-input-multiple-output (MIMO) antenna system integrated with a wideband metamaterial (MM) to reach high gain for sub-6 GHz new radio (NR) 5G communication. The four antennas of the proposed MIMO system are orthogonally positioned to the adjacent antennas with a short interelement edge-to-edge distance (0.19λmin at 3.25 GHz), confirming compact size and wideband characteristics 55.2% (3.25–5.6 GHz). Each MIMO system component consists of a fractal slotted unique patch with a transmission feed line and a metal post-encased defected ground structure (DGS). The designed MIMO system is realized on a low-cost FR-4 printed material with a miniature size of 0.65λmin × 0.65λmin × 0.02λmin. A 6 × 6 array of double U-shaped resonator-based unique mu-near-zero (MNZ) wideband metamaterial reflector (MMR) is employed below the MIMO antenna with a 0.14λmin air gap, improving the gain by 2.8 dBi and manipulating the MIMO beam direction by 60°. The designed petite MIMO system with a MM reflector proposes a high peak gain of 7.1 dBi in comparison to recent relevant antennas with high isolation of 35 dB in the n77/n78/n79 bands. In addition, the proposed wideband MMR improves the MIMO diversity and radiation characteristics with an average total efficiency of 68% over the desired bands. The stated MIMO antenna system has an outstanding envelope correlation coefficient (ECC) of <0.045, a greater diversity gain (DG) of near 10 dB (>9.96 dB), a low channel capacity loss (CCL) of <0.35 b/s/Hz and excellent multiplexing efficiency (ME) of higher than −1.4 dB. The proposed MIMO concept is confirmed by fabricating and testing the developed MIMO structure. In contrast to the recent relevant works, the proposed antenna is compact in size, while maintaining high gain and wideband characteristics, with strong MIMO performance. Thus, the proposed concept could be a potential approach to the 5G MIMO antenna system.

In this paper, a complementary split ring resonator (CSRR) loaded compact CPW-fed circular shaped monopole UWB antenna with dual band notch characteristics is designed on an FR-4 substrate. The propounded band-notched UWB antenna is integrated with two frequency selective surface layers referred as bandpass frequency selective surface (FSS-1) and reflector (FSS-2) to offer enhanced radiation performance. Bandpass FSS-1 enhances the gain of the antenna by improving directivity and reflector FSS-2 reflects back the backside radiation of the proposed antenna towards the forward direction thereby increasing gain and directivity of the proposed antenna. Furthermore, a two-element orthogonal MIMO antenna is proposed with improved gain using two FSS layers. The complete configuration of the proposed two-element MIMO antenna consists of CSRR-based radiating patches, monopole ground planes and two integrated FSS layers. The proposed MIMO antenna operates in UWB range from 3.46[Formula: see text]GHz to 16.02[Formula: see text]GHz with dual notches at 3.9[Formula: see text]GHz and 7.2[Formula: see text]GHz. Isolation between MIMO elements is greater than 23 dB. Both antennas are fabricated and investigated at 5.9[Formula: see text]GHz for vehicular communications. Maximum gain improvements of 8 dB and 6.4 dB are observed in case of the presented single element and MIMO antenna within the entire operating band due to the integration of dual FSS layers. The diversity performance of the suggested MIMO antenna is investigated by analyzing mean effective gain, envelope correlation coefficient, channel capacity loss and diversity gain parameters. The proposed MIMO antenna is a suitable candidate for vehicular and UWB wireless communication applications.

The present work represents polarization reconfigurable MIMO antenna which is design to work at 2.4 GHz (WLAN) and C band application. An inverted U-shaped slot and two PIN diodes per radiator are incorporated in the circular patch antenna to achieve polarization reconfigurability between Linear and Circular polarization (RHCP or LHCP). A simple rectangular strip is utilized between the radiators to achieve isolation improvement from -14 dB to -22dB in the proposed design. Computer Simulation Technology (CST) 2018 is used to design and validate the polarization reconfigurable MIMO antenna with sufficient isolation. Surface current distribution, Envelope Correlation Coefficient (ECC) and Diversity Gain (DG) and axial ratio are calculated using simulation software and used to validate circularly polarized MIMO design’s diverse behavior. The design is fabricated in low-cost FR-4 material and measurement is done to verify the simulation results. The measurement results show close agreement with simulated results and proves that the proposed design can be a better candidate for WLAN and C band application with polarization reconfiguration properties.

This paper proposes the design of a compact sub-6 GHz four-port flexible antenna for utilization in 5G applications. A two-arm monopole with a coplanar waveguide feed line printed on a flexible substrate was proposed to shape the single-element antenna. The single element was designed, fabricated, and measured first; then, four copies of the single element were organized on a single flexible substrate to compose the four-port antenna. The MIMO antenna was simulated, fabricated, and experimentally measured. All the simulations and measurements of the flexible single element and MIMO antennas are presented. The presented MIMO antenna showed good impedance characteristics, with a deep level of −24 dB from 3 to 4.12 GHz. The antenna had omnidirectional and bi-directional patterns in the φ = 0° and φ = 90° planes. As an important parameter evaluation for MIMO, the mutual coupling between the different ports was investigated. The diversity gain (DG), the total active reflection coefficient (TARC), the mean effective gain (MEG), the envelop correlation coefficient (ECC), and the channel capacity loss (CCL) parameters were investigated and showed good performance. All the obtained simulation results were in a high degree of agreement with the measurement results, supporting the usage of the suggested antenna in 5G communications.

In this work, an ultra-wideband graphene-based micro-sized circular patch-shaped Yagi-like MIMO antenna was investigated over 1–30 THz of the frequency spectrum. The proposed antenna structure was designed over a polyimide substrate with 620 × 800 µm2. This antenna was radiated over three bands over 1–30 THz. The maximum bandwidth achieved 10.96 THz, with −26 dB of the return loss isolation. These three bands were also mathematically analyzed using various MIMO antenna parameters to match the MIMO antenna criteria. This antenna provided all the accepted results as per the limits set by these antenna parameters. The effect of the different port excitation on the change of directivity of the overall structure is also reported. The MIMO antenna parameters such as TARC (Total Active Reflection Coefficient), ECC (Envelope Correlation Coefficient), MEG (Mean Effective Gain), CCL (Channel Capacity Loss), and DG (Directivity Gain) were investigated for the proposed structure. These values were also identified to check the compatibility and challenges associated with short-distance communication. The suggested THz MIMO antenna provides the operating bands of 1–10 THz and 15–30 THz, with good isolation values. An average of 7 dB gain was observed in the 2 × 2 antenna structure. The newly developed MIMO antenna in the THz frequency range may be used for high-speed short-distance and terahertz communications.