Cardiovascular diseases (CVDs) are one of the leading causes of death globally. The Internet of things (IoT) enabled with industrial, scientific, and medical (ISM) bands (2.45 and 5.8 GHz) facilitates pacemakers to remotely share heart health data to medical professionals. For the first time, communication between a compact dual-band two-port multiple-input-multiple-output (MIMO) antenna (integrated inside the leadless pacemaker) and an outside-body dual-band two-port MIMO antenna in the ISM 2.45 and 5.8 GHz frequency bands is demonstrated in this work. The proposed communication system offers an attractive solution for cardiac pacemakers as it can operate on a 5G IoT platform while also being compatible with existing 4G standards. The experimental verification of the proposed MIMO antenna low-loss communication capability is also presented by comparing it to the existing single–input–single–output communication between the leadless pacemaker and outside body monitoring device. In this direction, Medtronic® introduced the world's first remote cardiac monitoring system in 2002, which has been used by two million patients worldwide. Remote monitoring not only helps to limit in-person contact with other patients, healthcare workers, and physicians, but it also reduces exposure to various viruses, including COVID 192. Several studies using a patch antenna for a leadless pacemaker have been published in the past6. Leadless pacemaker antenna designs are classified into two types: conformal8 and flat6. The flat antennas must be placed on the PCB holder or on top of the telemetry module inside the pacemaker capsule, while the conformal antennas must be wrapped around the curvature of the pacemaker capsule. The reported antennas were operated in the medical implant communication system (MICS)/400 MHz band and the industrial, scientific, and medical (ISM)/2.45 GHz band6. Recently, in9 and10, two implantable antennas were proposed operating in single ISM 2.45 GHz band, and a multi-band antenna was proposed in11. However, due to the single antenna element, such antenna systems will not be suitable for next generation pacemakers. A leadless cardiac pacemaker (LCP) outfitted with a multiple-input-multiple-output (MIMO) antenna, as shown in Fig. 12 while also having power telemetry can be achieved. When compared to a single antenna system, MIMO communication systems offer high capacity and low-loss transmission/reception without requiring additional power13.Low-cost health-care facilities are required to promote healthy ageing and reduce premature deaths from cardiovascular diseases (CVDs)15. Despite the fact that antennas in14 and15 were proposed for implantable applications, the authors did not investigate specific absorption rate (SAR), and the MIMO antenna reported in14 had poor isolation (12 dB). In16, a two-port single band (ISM 2.45 GHz) MIMO antenna with two different antenna elements was presented. In17, an implantable antenna with a partial and slotted ground plane was proposed, which operated in a single band (ISM 2.45 GHz) and had inter-element isolation of 16 dB. In18, a two-port MIMO antenna with isolation of 26 dB was reported. In19, a four-port head implantable MIMO antenna with high port isolation and sufficient gain was proposed, but the antenna size was quite large. In20 and21, implantable MIMO antennas were proposed, both of which operated in single ISM 2.45 GHz frequency band with slot loaded ground planes. In22 and23, two implantable MIMO antennas were proposed, where the MIMO antenna in22 had slotted ground with two shorting pins, whereas the MIMO antenna in23 had a complete ground plane. In the above-mentioned implantable MIMO antennas, defects or slots on the ground surface have a significant impact on the performance of the antenna. It is well understood that an antenna with a complete ground plane ensures radiation in the broadside direction with the required high front-to-back ratio, i.e., outwards from the body towards the external monitoring device.In the literature, there are few works reported on implantable MIMO antennasTo date, there has been no article in the open literature on a compact multi-band MIMO antenna system for leadless transcatheter pacemaker (TCP). In this paper, an ultra-compact two-port MIMO antenna system with dimensions of 3.4 mm × 6.6 mm × 0.254 mm is presented, which can be easily integrated with commercial pacemakers (Medtronic® Micra TCP and Nanostim® LCP).27.The proposed antenna operates in dual-frequency bands (2.45 GHz and 5.8 GHz), has a flat profile, and offers satisfactory gain in the reported bands. The proposed MIMO antenna has the smallest footprint as compared to the previously reported implantable MIMO antennas. Here, higher ISM frequency bands that are compatible with Wi-Fi and Bluetooth technologies are used in the IoT environment. In order to ensure patient safety due to the long-term use of the pacemaker, loop antenna is chosen, which confines current to the radiator and results in low radiation effects due to less interaction with biological tissues28. Furthermore, a communication system is simulated in the Ansys HFSS® software to validate far-field communication performance of the proposed MIMO antenna. For this purpose, the MIMO TCP system is implanted in the multi-layer canonical heart phantom, and the external MIMO antenna is placed at different distances in the far-field region. The proposed antenna prototype is fabricated and packed inside a ceramic alumina capsule (dimensions similar to the Medtronic's Micra TCP) along with dummy electronics  and a battery, and experimentally validated in a heart muscle gel  phantom. Also, the communication is configured for MIMO and single port antenna, and the results are compared to illustrate the advantages of MIMO over single–input–single–output (SISO) communication.The proposed implantable MIMO antenna is simulated in the canonical model of the heart muscle after being placed at the top of the telemetry module inside the TCP system, as perλ0/4 from the antenna. The heart muscles are then designed as a cuboid with dimensions of 50 mm × 50 mm × 120 mm, and it is positioned in the center of the radiation box. In order to make the phantom more realistic, skin and fat layers of 4 mm thickness are added on top of the muscle layer, as shown in Fig. 30. The housing of the leadless pacemaker system is designed in the center of the heart muscles  with dimensions of 3.4 mm × 6.6 mm × 0.254 mm at the top of the telemetry module of the TCP system. A fractal antenna design is chosen  is ~ 17 mm inside the heart muscle, but this much area is not available inside the leadless pacemaker. Therefore, the design begins with an open loop antenna on the substrate of 3.4 mm × 6.6 mm, which is the first stage of the Hilbert curve, as shown in Fig. λg/2) is 5.9 mm, as shown in Fig. At the targeted frequency of 2.45 GHz, the guided wavelength , a good isolation of > 22.5 dB is achieved.In step-4, a π-shaped metal strip connects the two halves of the antenna elements, as shown in Fig. An open-loop square section is introduced at the end of each antenna element, as shown in Fig. εr = 3) with a thickness of 0.762 mm. The design of both antennas and their scattering parameters are shown in Fig. λ0–2.45 GHz) apart. The reflection coefficients of a single-port antenna are shown in Fig. A conventional rectangular patch antenna and a two-port MIMO antenna are designed as outside-body antennas, and fabricated on the Rogers 3003 substrate 38 is shown in Fig. Figure 11| and |S22|) of Antenna 1 and Antenna 2 and isolation (|S12| and |S21|) between antenna elements is shown in Fig. Next, comparison of the measured and simulated reflection coefficients  and 1.22 GHz (1.73–2.95 GHz), respectively, and, at 5.8 GHz, the simulated and measured impedance bandwidths are 1.7 GHz (4.5–6.2 GHz) and 1.91 (5.00–6.91 GHz), respectively. As shown in Fig. Single-port implantable antenna and outside-body antennas fabricated prototypes are shown in Fig. θ = 0˚)). The measured gain values are less than the simulated values, likely due to implantation depth variation (because of human error) in the muscle phantom during measurements. It is very common for ultra-compact implantable antennas to have low gain values due to high losses in biological tissues, as per39. Therefore, the proposed antenna has the minimum gain value when compared to the other reported implantable MIMO antennas in Table E (ϕ = 0˚) and H (ϕ = 90˚) planes demonstrate diversity, making the proposed antenna in an integrated approach an attractive entrant for efficient wireless communication in a lossy human body environment.The gain of the MIMO antenna in the muscle phantom is measured in an anechoic chamber, as shown in Fig. H-plane. At 2.45 GHz, simulated and measured peak gain values are 3.79 dBi and 3.74 dBi, respectively. Radiation patterns for single-port outside-body antenna and single-port implantable antennas are shown in Figs. H-plane at both the resonant frequencies (ISM 2.45 and 5.8 GHz), and in the E-plane, radiation pattern is eight-shaped. Simulated and measured values of the peak gains for outside-body single-port antennas are 2.8 dBi and 2.7 dBi, respectively, at 2.45 GHz frequency. Whereas, at 5.8 GHz, simulated and measured peak gains are 3.6 dBi and 3.45 dBi, respectively.A comparison of simulated and measured radiation patterns of outside-body two-port MIMO antenna at 2.45 GHz and 5.8 GHz is shown in Fig. Single-port implantable antenna was integrated into the biocompatible ceramic alumina’s capsule housing along with ICs and battery, as shown in Fig. 40.The envelope correlation coefficient (ECC) of a MIMO antenna indicates how independent the antenna elements are of one another. Ideally, there should be zero correlation between the antenna elements in order to avoid undesired coupling of the power radiated by each antenna. But practically, ECC < 0.5 is acceptable. ECC is calculated with the help of the 3D radiation pattern, as explained in41.It can be noted from Fig. Simulated and measured DG is close to 10 dB, as shown in Fig. 42 are considered. As per the safety standards the Average SAR (ASAR) value for 1 g/10 g of human tissue in a shape of a cube cannot be greater than 1.6/2.0 W/kg. All the SAR values (1 g/10 g) correspond to the input power of 1 W. Although ASAR value should be high at high frequency, in the present case, it is low because at 5.8 GHz intensity of the current is low as compared to the 2.45 GHz and causes a low value  of SAR at high frequency, as shown in Fig. 43; hence, on the basis of results, the MIMO TCP system will be safe for long-term use inside the human body.The proposed TCP MIMO antenna system is checked in terms of safety by evaluating the SAR when the prototype lies in the multilayer human heart phantom. For this purpose, the new guidelines of International Commission on Non ionizing Radiation Protection (ICNIRP) and IEEE C95.1-2019 standards12, a MIMO system was used to extend the transmission range for non-biomedical applications. The same concept is tested in this work for implantable TCP system as it is also enabled with remote monitoring, and by using the MIMO communication technology, one can achieve increased transmission range (or received power for fixed distance), hence improving the performance of the TCP system. Furthermore, with the deployment of 5G networks, there is a strong need to replace conventional single port antennas with MIMO antennas, as MIMO antennas are one of the requirements for 5G communication. Considering all of these factors, SISO and MIMO communications are established and compared in the simulation and anechoic chamber to validate the advantage of MIMO communication over SISO communication.In this section, the single-port antenna TCP communication system and MIMO antenna TCP communication system in the simulator and anechoic chamber  are explained and compared. InIn a leadless pacemaker communication system, an external device receives data wirelessly from the implanted device (TCP) and transmits it wirelessly to a healthcare professional. The implanted leadless pacemaker (transmitter) and the external device (receiver) that receives the patient's data use a single-port antenna for both transmission and reception, which is referred to as a SISO communication system, as shown in Fig. D2/λg), where D is the largest dimension of the antenna and A single antenna pacemaker consists of a dual-band (ISM 2.45 GHz/5.8 GHz) antenna, battery, and ICs that are integrated inside a biocompatible ceramic alumina capsule housing, as shown in Fig. S21) between the implantable TCP antenna (transmitter) and the single-port antenna (receiver) using the following formula:In the present case, the far-field distance is 5.1 mm at 2.45 GHz and 12.13 mm at 5.8 GHz. Thus, distances greater than 12 mm are in the far-field range. In this work, a distance of 20–200 mm is used to compare the communication system in terms of losses or received power strength. Therefore, for the evaluation of the received power strength, distances ranging from 20 to 200 mm are taken into account, and the received power is calculated using the transmission coefficient  and ICNIRP guidelinesPR) at 20 mm distance (minimum) is − 42.4 dBm, while at 200 mm distance, the power received is − 58 dBm. Whereas, at 5.8 GHz, the maximum received power is − 44.2 dBm at 20 mm and − 57 dBm at 200 mm, as shown in Fig. Figure The received power measurements for single-port antenna communication are performed inside the anechoic chamber, as shown in Fig. The TCP system is immersed in the heart muscle gel phantom and fed by 8 dBm power (at 2.45 GHz) and 11 dBm power (at 5.8 GHz) from the signal generator via a power amplifier, as shown in Fig. R1 due to transmitting antenna T1, R1 due to transmitting antenna T2, R2 due to transmitting antenna T2, and R2 due to transmitting antenna T1. In this case, a two-port dual-band MIMO TCP antenna is used on the transmitter side, and a two-port dual-band patch antenna is used on the receiver side.Multiple antennas are used on the transmitter and receiver sides of the MIMO communication system. The proposed work has considered a (2 × 2) MIMO antenna system, as shown in Fig. PR can be calculated by using Eq.  resonances, as shown in Fig. The presented work uses a single port monopole and two-port MIMO monopole antennas as outside-body antennas to demonstrate single port/MIMO antenna communications. The omnidirectional radiation pattern of the monopole antenna makes it a good choice for outside-body communication as there is no need for alignment with the implantable antenna. Furthermore, by using a high gain omni-directional MIMO antenna array instead of a simple monopole antenna increases the communication range or reduces the losses for fixed communication distance. Also, this study found that MIMO antenna communication not only provides long range/low-loss communication for present IMDs, but it is also compatible with future IMDs on the 5G-IoT platform and can participate in real-time monitoring of human-heart for future leadless pacemakers.This paper proposes an ultra-compact MIMO antenna integrated into the leadless pacing system, which enables low-loss MIMO communication to the external MIMO antenna for remote cardiac monitoring on 5G IoT platform. Here, in order to check the low-loss capability of MIMO communication, two types of far-field communication systems are realized: one with a single-port antenna and the other with MIMO antenna in the simulator and anechoic chamber. The performance of both communication systems is compared by comparing their received power. A comparison of simulated and experimental results shows that MIMO antenna communication system receives more power than SISO communication system at both frequency bands (ISM 2.45 GHz/5.8 GHz). Hence, due to its ultra-compact size and higher far-field received power in both frequency bands, the proposed MIMO antenna communication system is suitable for remote health monitoring and wireless power transfer for commercial leadless TCP systems: Micra's TCP and Nanostim's LCP in 4G as well as in 5G IOT based remote monitoring applications.


The simulated antenna’s input reflection coefficient (S11) results and the far-field measurements show good agreement. The fabricated prototype achieves peak gain values of 2.8, 3.8, and 4.7 dBi, respectively, and bidirectional radiation characteristics. A comparative study with other recent publications is implemented to validate the consistency of the design.A triple-band microstrip patch antenna designed for the IEEE 802.16e WiMAX, IEEE 802.11a WLAN, C-band downlink communications, and Ku-band radar recent applications is suggested in this article. The planned antenna operates at 2.45, 6, and 14 GHz resonant frequencies. The antenna fulfilled triple-band physical characteristics covering industrial, scientific, and medical (ISM) bands between (2.1–2.8) GHz; (5.6–6.5) GHz for wireless local area network (WLAN) or ultra-wideband (UWB) services; and 12.7–16 GHz for future two-way 5G:6G either broadcasting or mobile satellite communications. To achieve better return loss performance, parametric studies are carried out using Microwave Studio (CST MWS). The proposed antenna is designed on the FR4 as a hosting medium of total size 46 × 38 × 1.6 mm Nevertheless, the work on 5G has advanced to 6G and will be properly triggered over the rest of this decade. 5G Advanced will continue to improve end-to-end communication and wireless network performance, bring new efficiencies, and launch the technical foundation for 6G (the next innovation platform for mobile).1. Several demands on the antenna, such as simplicity, size miniaturization, power consumption, and inexpensive cost, are extremely important for cutting-edge wireless technologies. Numerous techniques have been considered to provide a compact antenna size; however, each of them has some limitations. The best compact-size antenna structures that have been considered recently are the micro-strip patch antennas, which can be easily united into wireless communication devices. Generally, the microstrip patch antenna is structured by a thin metal layer attached to a dielectric substrate backed with thin metals and is simply printed on the PCB's surfaces for different wireless terminal equipments2. The growth of multi-functional UWB wireless devices uses high data rates, long battery life, and small antenna sizes. These antennas should fulfill the electromagnetic compatibility (EMC) requirements by providing less exposure to electromagnetic (EM) radiation to be safe for human tissues. Moreover, micro-strip antennas play an indispensable part in UWB systems; typically, they aid in the emission of very narrow pulses, each with nearly 1 ns and 1 GHz bandwidth. UWB antennas cover two broad ranges: the lower band, which extends from 3.1 up to 5.1 GHz, and the upper band, which ranges from 5.85 up to 10.6 GHz. The leading wireless technology corporations are now on track with the upcoming wireless systems, such as beyond 5G (B5G)/6G wireless sensor technologies and beyond the 6 GHz frequency (WiFi-6E)4. GHz Wi-Fi will be frequently engraved into the history of wireless technology by the representatives of the US telecom-regulator Federal Communications Commission (FCC), which voted to utilize 6 GHz in Wi-Fi despite the 1.2 GHz spectrum6. Wi-Fi 6 diminishes the transmission and delay times of wireless networks queued for users7. High efficiency, reasonable gain values, and a small size antenna are preferred for many standards such as IEEE 802.16 (WiMAX), IEEE 802.11ac, and IEEE 802.11n (WLAN) and 5:6 GHz Wi-Fi communication devices8. Researchers presented various antenna types to meet the requirements of the most current wireless applications. The well-known microstrip antenna types are target specific, UWB, reconfigurable, dual, triple, and multiband antennas. Moreover, these antenna types have implemented many techniques, like Defected Ground Structure (DGS) and metamaterials, to achieve wideband capabilities9. In10, a micro-strip antenna containing DGS with a total size of (59.5 × 47 × 1.6) mm3 is presented. It achieved triple-band operation at the following resonating frequencies: 1.57, 2.45, and 3.53 GHz. A compact UWB inverted triangular antenna with dual-notch band characteristics is presented in11. It offers three operational frequency bands in the UWB range, which are between 3–4.17, 5.33–6.5, and 8.9–12 GHz, respectively. A compact printed UWB antenna with tri-notched characteristics at 3.5, 5.5, and 8.1 GHz with a total size of (30.2 × 25 × 0.762) mm3 was introduced in12. A quadruple-band notched UWB antenna was presented and fabricated in13. It has a size of 32 mm × 30 mm × 1.6 mm and its operation covers four-notched bands at 3.1–3.6, 4.9–6.1, 7.5–8.4, and 10.2–11 GHz, respectively. An UWB MIMO antenna is presented in14, composed of a chip antenna, an isolator stub, and a printed circuit board (PCB) with a partial ground plane. A chip antenna patch size of 10 × 10 × 0.8 mm3 embedded on FR4 dielectric substrates, besides a PCB of 30 mm × 30 mm, provides operation at 2.45:9 GHz and a maximum peak gain of 4.5 dBi. In15, a reconfigurable pattern monopole antenna including two pin diodes with an overall size of 32 × 59 × 0.8 mm3 is considered. Its operating frequency band is 3.36 to 3.6 GHz, with realized gain and efficiency of 2.13: 4.93 dBi and 62% to 82%, respectively. In16, a patch antenna that operates in UWB-MIMO applications and has (34 mm × 34 mm × 1.6 mm) total dimension with notched triple band characteristics is proposed. It covers the subsequent notched bands (3.3:3.9), (5:6), and (7.4:8.5) GHz with a radiation efficiency lower than 50% and from 75% up to 90% in the other UWB frequency bands. A sub-6 GHz 5G four-element triple-band MIMO antenna is presented in17 for wireless applications. It is designed by using FR-4 substrate to operate in the following triple bands: 3.72–3.82, 4.65–4.76, and 6.16–6.46 GHz, with a dimension of 16 mm × 16 mm × 1.6 mm and an average gain equal to 2.5 dBi. In18, a four port UWB-MIMO antenna constructed on an FR4 substrate with an overall size of (30 × 30 × 1.6 mm3) is presented. The antenna's operating frequency band is (3.1–12) GHz, and it achieved a maximum gain of 6.2 dBi and an efficiency of 87%. A triple-band mm-wave patch antenna is presented in19 with triple resonating frequencies at 2.4, 5.5, and 28 GHz. The antenna dimensions are 45 × 40 × 0.508 mm3, and it provides gain values of 1.95, 3.76, and 7.35 dBi, respectively. A radiating MPA is introduced in20 for conventional sub-6 GHz/5G applications. It uses an Arlon-AD 300C substrate with a 52.92 × 55.56 × 1.2 mm3 antenna size and achieves a gain value of 7.15 dBi at a frequency of 5.65 GHz. In21, a C-shaped ring antenna integrated with the structure of an artificial magnetic conductor (AMC) and a Styrofoam layer is presented. It has a total size of 54 × 54 × 3.9 mm3 and operates at a 2.4 GHz resonating frequency with a 6.21 dB gain and 81% efficiency. As mentioned in22, a planner monopole antenna with a partial ground plane is designed with a total dimension of 38 × 50.5 × 1 mm3. It achieves operation in the ISM band from 2.075 up to 2.625 GHz with a peak gain of 7.76 dBi and an 80.12% efficiency value. An antenna array module for in-time operation at 3.5 GHz (sub-6 GHz) and 26 GHz mm-wave frequencies is presented in23. The antenna modules are fabricated on a commercial FR-4 substrate with a total size of 154 mm × 66 mm × 0.6 mm. It achieves an input impedance matching -10 dB in the sub-6 GHz and mm-wave bands, respectively, to support the feasibility of the recent 5G smartphones.In the last few years, wireless communication parts used in 3G, 4G, and 5G networks have undergone astonishing developments. Their applications, like GPS, Wi-Fi, IR, and several others, are developing at enormous speed as well. An essential component of modern wireless communication systems is the antenna, which has displaced cables. Also, the rapid progression of multi-purpose communication devices requires operation in more than one frequency band. Correspondingly, research related to wireless communication systems is increasing, especially in dual, triple, UWB, and multiband antennas3 dimensions and then combined with a planar T.L. feeder. It is simulated by means of CST MWS, while the antenna prototype structure was developed during the design process. As a result, this antenna was able to be operated in triple-band operation with gain values reaching up to 6 dB, more than 85% radiation efficiency, and bidirectional radiation characteristics.In this study, a microstrip patch antenna has been designed to enable triple-band operations at 2.5, 6, and 14 GHz. Its double circular ring patches are etched on the upper MPA side, while a partial-rectangular DGS is embedded on the bottom side of the antenna. The whole antenna structure is fabricated using a FR4 (5880) substrate of 46 × 38 × 1.6 mmThe substantial features of the planned antenna have been listed as follows: (1) Simple circular radiators and a partial ground plane are loaded on a single square-shaped microstrip patch to achieve triple-band performance. (2) It provides three operational bandwidths using a simple geometrical arrangement, a T.L. feed, and a DGS for ever-changing the operation frequency to lower and upper bands without increasing the antenna size, and (3) the combination of compact size, three operating bandwidths, high efficiency, and high gain recommends future usage of the presented antenna in upcoming wireless communication and LAN network systems. (4) the ".The paper is divided as follows: Section "Antenna design and working principle" describes the antenna's design and working principles, along with the analytical design equations. In Section "Simulations resultsthe simulation results of the planned structures have been offered. Fabrication and tests are then presented in Section "Fabrication and tests"; finally, Sect. 5 presents the conclusion.The presented circular patch micro-strip antenna, along with the rectangular arms and the DGS, are mainly designed to cover the operational requirements at 2.45, 6, and 14 GHz frequencies. The whole antenna structure is embedded on the FR4-5880 commercial substrate; its dielectric parameters are, respectively, 1.6 mm substrate thickness 'h', substrate dielectric constant of 4.4, and 0.02 loss tangent. The planned antenna is constructed of two circular radiator elements supported by four rectangular arms on the upper patch layer, while the DGS is placed on the lower side. As a result, different resonance frequencies have been fulfilled. The designed structure is excited by means of a transmission feed line (T.L.). Since we recognize the importance of mathematical modeling in engineering design, we are dedicated to sharing our antenna design by using mathematical and computer tools to address the design challenges. Mathematical modeling is the act of using equations to represent a real-world situation in mathematical terms and then utilizing those equations to both understand the problem and uncover new features.24, the design of each circular patch starts by calculating its diameter D by means of the following equations:In relation to the elementary formulas present inwhere wherein the analysis of the upper rectangular arms and the DGS starts by calculating their widths The lengths and then the substrate effective dielectric constant will be calculated by:r is the substrate relative dielectric constant.wherein, the 25:3. The double circular patches with outer diameters D2 and D4 are taking place on the upper antenna's left and right sides, supported by vertical antenna arms L2 and L4, respectively; each has an inner circular slot. The small slots were loaded on the center of each circular patch of diameters D1 and D3 to improve the performance of the antenna structures and increase the operational impedance bandwidth25. To avoid the higher order modes operation and approve the 50Ω microstrip line matching impedance, the metallic T.L. cut-off frequency will be given by26.The initial dimension values for the rectangular and circular patches have been set according to the above equations. Then, the antenna parameters have been parametrically studied through the CST MWS software to get the best values for matching the designed antenna around the required resonances. The overall antenna optimum design parameter values are then listed in Table r & where c = 17.where 26. The reflection of the arriving wave is lessened according to the impedance matching methodology, therefore, a microstrip feedline with optimized dimensions Wo and 2 is loaded on a similar substrate for appropriate excitation. Accordingly, the appointed substrate parameters realize up to 16 GHz operating frequencies without the higher-order modes of operation26. The patch impedance 26.The accurate selection of the substrate's width to obtain a 50 Ω microstrip line and keep the minimum loss in microstrip line feed is  make them more resourceful than the feed line. Nevertheless, the shift around the frequency’s resonances takes place due to the effect of DGS underneath the various patches; these added resonances achieve a wider triple-band performance based on optimizing the DGS to increase the operating bandwidth around the resonating frequencies29. Figure 25.As a result of the inherent analysis, good-looking surface current distribution features, and the various resonances, a straightforward perspective of the proposed antenna's performance is realized. The manufacturing process was then executed to confirm the preceding simulation results and validate the physical characteristics of the proposed design. The input reflection coefficient (S11) parameters of the fabricated antenna prototype were measured using the 50 Ω port of the ZVA 67 Rohde and Schwarz vector network analyzer (VNA). The test arrangement is depicted in Fig. 30. Table Further inspection was done on the proposed antenna by examining the 2-D radiation characteristics at some valid frequencies and antenna gain values over the related bandwidths. The anechoic chamber is utilized during the measurement as depicted in Fig. 19 in Table The radiation patterns at 2.45 GHz (first band), as depicted in Table 29. As shown Fig. 31.Additionally, the simulated versus measured 2-D gain values of the fabricated antenna were verified in Fig. The measured and simulated antenna radiation efficiency over the overall frequency range is illustrated in Fig. 33. Figure Generally, the equivalent circuit model can be done using a parallel or series RLC circuit, where the microstrip patch antenna performs a bandpass filter. The antenna attenuates all frequencies except those in the desired frequency range. As a result, the proposed antenna's input reflection coefficient (S11) has been equivalently modeled using parallel resonant circuits via the Advanced System (ADS) toolbox. The equations relating the required bandwidth and resonant frequency with R, L, and C components are completely described inIn conclusion, Table In this work, an UWB microstrip patch antenna operating in triple-band, covering 2.45, 6, and 14 GHz resonance frequencies was engineered. These frequencies have implications for modern wireless technologies, especially 5G/6G applications. The design steps of the proposed antenna are discussed in detail. It is based on reducing the overall antenna size by using circular-radiator patches besides DGS, all printed on the same substrate. The strong couplings between both driven and parasitic patches offer triple-band operation with three different frequency resonances. Moreover, this configuration experimentally achieves proper impedance matching, gain, and efficiency values. The radiation characteristic enhancements of the proposed antenna in the overall operating frequency ranges are thus fulfilled. The fabricated prototype exhibits triple-band antenna performance at the definite frequencies of input reflection coefficients more than − 10 dB. The results show that the efficiency and gain values of the planned antenna reach up to 87% and almost 6 dBi with good bi-directional radiation characteristics.


A low-profile broadband dual-polarized antenna is investigated for base station applications. It consists of two orthogonal dipoles, fork-shaped feeding lines, an artificial magnetic conductor (AMC), and parasitic strips. By utilizing the Brillouin dispersion diagram, the AMC is designed as the antenna reflector. It has a wide in-phase reflection bandwidth of 54.7% (1.54–2.70 GHz) and a surface-wave bound range of 0–2.65 GHz. This design effectively reduces the antenna profile by over 50% compared to traditional antennas without an AMC. For demonstration, a prototype is fabricated for 2G/3G/LTE base station applications. Good agreement between the simulations and measurements is observed. The measured −10-dB impedance bandwidth of our antenna is 55.4% (1.58–2.79 GHz), with a stable gain of 9.5 dBi and a high isolation of more than 30 dB across the impedance passband. As a result, this antenna is an excellent candidate for miniaturized base station antenna applications. As wireless communication networks expand, base station antennas are critical components in these systems. However, they face challenges, such as large physical dimensions and limited bandwidth . Dual-poλ0 [λ0 [λ0 represents the wavelength in free space at the center frequency). However, they can provide narrow −10-dB impedance bandwidths of only 15.6% [Dual-polarized planar dipole antennas have attracted considerable attention because of their wide bandwidth and pattern stability. Low-profile designs can be achieved using bowtie-shaped crossed-dipole antennas and Huygens dipole antennas, with profiles of 0.088λ0 [λ0 , respectly 15.6% . To enhaly 15.6% ,12. Theyly 15.6% ,12. As aly 15.6% ,14. GrooFrequency Selective Surfaces have recently obtained much attention due to their unique properties in favor of antenna performance. A frequency selective surface (FSS) is a periodic structure, typically a thin sheet or a grid, that has unique transmission and reflection properties for different electromagnetic frequencies. These surfaces are designed to either pass or block specific frequency ranges when subject to electromagnetic radiation. The FSS is useful in antenna design, such as reducing decoupling ,16 and i0 from the radiator. As a result, this characteristic enables them to reduce the antenna profile, leading to compact and low-profile antenna designs. In [λ0. However, its −10-dB impedance bandwidth is only 15.6% (2.36–2.76 GHz). In [0.As a kind of FSS, the artificial magnetic conductor (AMC) is useful in addressing antenna size problems. It can replace a traditional metal conductor as a new reflector type for base station antennas. They exhibit properties of magnetic conductors with a zero-degree phase shift upon reflection. The in-phase reflection avoids the 180-degree phase change of the electromagnetic wave when it is reflected from the metal plate, thus, eliminating the need to set the reflector back at 1/4 λGHz). In , using m0 and 0.15λ0. These antennas have a wide AMC bandwidth of more than 40%. However, both designs suffer from strong surface waves, leading to decreased antenna gain [Air gap technology has obtained much attention due to its ease of fabrication and high performance in antenna applications . Adding nna gain  or high nna gain . TherefoIn this paper, a low-profile broadband dual-polarized dipole antenna using a novel AMC reflector is investigated. Using the Brillouin dispersion diagram, the AMC is designed to suppress the surface-wave effect and decrease the antenna height. As a result, the proposed antenna has a high efficiency and low antenna profile. The fork-shaped lines feed the antenna without a direct connection, giving a broad impedance bandwidth. The parasitic strips reduce cross-polarization. The evolution of the proposed AMC and dipole antenna is analyzed using equivalent circuits and Smith charts. A prototype that operates in 2G/3G/LTE base station applications was designed and fabricated. The reflection coefficient, radiation pattern, antenna gain, and antenna efficiency are measured. Reasonable agreement between the measured and simulated results is obtained.φ = ±45° and are represented as dipoles 1 and 2. w1 = 3.6 mm and four mirror-symmetrical etched slots. It should be mentioned that one of the dipole arms Is soldered directly to the feeding structures, while the other arm is fed via space coupling. This method is designed to obtain a wide −15-dB impedance matching bandwidth. The novel AMC consists of two metal layers, one substrate, and air layers. Periodic patches are its first metal layer printed on Layer 3 of Sub. 2, with the interval gap of g = 2 mm and patch width of w = 13 mm. The second metal layer is aluminum ground. Sub. 1 and Sub. 2 are FR4 substrates . Crossed dipoles are placed at a height of 5.5 mm from the AMC surface. Plastic pins are used to locate layers precisely. w = 13 mm, a substrate-layer height of dh = 1.2 mm (0.0088λ0), and an air-layer height of ah = 12 mm (0.0880λ). AMC1 and AMC2, which are conventional AMCs with the same patch size and gap width but different substrate-layer heights , were simulated for comparison. Generally, the in-phase reflection bandwidth is the frequency range in which the reflection phase is between −π/2 and π/2. With reference to the figure, the in-phase reflection bandwidths are 9.8%, 39.4%, and 54.7% for AMC1 (4.57–5.04 GHz), AMC2 (1.67–2.49 GHz), and the proposed AMC (1.54–2.70 GHz), respectively. Compared with the proposed AMC, AMC1 lacks the air layer, giving a zero-phase reflection frequency of 4.82 GHz that is out of the operating bandwidth of 2G/3G/LTE. It is worth mentioning that AMC2 has almost the same zero-phase reflection frequency, however, it has a narrower in-phase bandwidth and a worse reflection coefficient than the proposed AMC. Therefore, our AMC is a good alternative to the metal ground due to its wideband. pL. Another inductance dL is created by the total substrate, including the air and the dielectric. Gaps between adjacent patches form a grid capacitance pC. As a result, the resonant frequency and bandwidth of the proposed AMC can be represented by Equations (1) and (2), which show the relationship between parameters on the resonant frequency and bandwidth coefficient.1 and AMC2, the proposed AMC has higher profiles and, thus, a larger dielectric inductance dL. Since the derivative of Equation (2) with respect to dL is positive, the bandwidth is positively related to the dielectric inductance dL. Therefore, AMC2 and the proposed AMC have a wider bandwidth. In addition, the dielectric substrate of AMC2 is thicker, which increases dielectric losses and manufacturing costs. The proposed AMC has the widest bandwidth. The surface impedance of AMC can be represented by: The proposed AMC unit can be equivalent to an LC parallel resonant circuit using the equivalent circuit analysis method (ECM) ,24, as isη tends to infinity. The reflection coefficient of AMC can be calculated by At the parallel resonant frequency (using Equation (1)), the denominator of Equation (3) is equal to zero, and thus, the surface impedance 0 to 0.13λ.Generally, a surface wave will be excited when electromagnetic waves reflect from the ground, deteriorating antenna performance. 21f in the lower-frequency band. Therefore, Dipole II has a wide −10-dB impedance bandwidth of 41.7% (1.67–2.55 GHz). This can be well-demonstrated by 11f and 23f is the same.Dipole III is obtained by adding rectangular slots on Dipole II. The introduced rectangular slots effectively make two different resonant modes close seen in c, resultLC resonator circuit (fL and fC) and a π-shaped network . Dipole III is obtained by cutting corners and opening rectangular slots in Dipole I. Dipole I can be expressed as a parallel RLC resonator circuit . The corners and rectangular slots can be expressed as a parallel RLC resonator circuit . When one loop dipole is excited, the other acts as a coupled loop resonator. Consequently, they are configured in parallel within the circuit. The adjacent gaps between two dipoles are modeled as a π-shaped network .The equivalent circuit model of Dipole III is shown in fL = 1.73 nH, fC = 0.10 pF, g1C = 3.48 pF, g11C = 0.43 pF, g12C = 4.17 pF, d1R = 99.9 Ω, d1L = 1.07 nH, d1C = 0.36 pF, s1R = 5.02 Ω, d1L = 1.07 nH, s1C = 2.23 pF, g2C = 2.45 pF, g21C = 0.43 pF, g22C = 4.17 pF, d2R = 5.24 Ω, d2L = 0.35 nH, d2C = 3.18 pF, s2R = 5.24 Ω, d2L = 0.35 nH, s2C = 2.93 pF. By utilizing the proposed equivalent circuit and circuit analysis software, we can expedite the design process of the proposed antenna, particularly when attempting to bring two resonant modes into proximity. The values of circuit parameters can be obtained by using a curve-fitting method. The extracted results are m × m) of AMC units. With reference to AMC is employed to replace the traditional metal ground, thereby increasing the antenna gain and maintaining a low profile. Therefore, it becomes crucial to select an appropriate quantity of AMC units. This strategic selection aims to ensure that the antenna exhibits a broad, high-gain bandwidth, adequately covering the frequency ranges of 2G (1.71–1.92 GHz), 3G (1.88–2.17 GHz), and LTE (2.3–2.4 GHz and 2.5–2.69 GHz) networks. E- and H-plane radiation patterns can be obtained by the loading strips. It is worth mentioning that, using this method, the cross-polar fields in the two principal cutting planes decrease by more than 12 dB.To verify the idea, a prototype of the proposed antenna was fabricated, as shown in θ = 0°. With reference to the figure, reasonable agreement can be found between the simulated and measured results. The ripple in measurement is less than 1 dB caused by experimental imperfections. The measured gain varies between 8.3 and 10.8 dB over the frequency range (1.62–2.82 GHz) shown in θ < 60°) in the measurements. Results of Port 1 are only shown due to the geometric symmetry of our crossed-dipole antenna.0. In addition, four parasitic metal strips have been introduced to reduce the cross-polar field and, thus, increase the antenna gain in its high-frequency impedance passband. To verify the idea, a prototype has been simulated, fabricated, and measured. A measured overlapping bandwidth of 55.4% (1.58–2.79 GHz) has been obtained. Its maximum measured realized gain is 10.8 dB at 2.6 GHz. Additionally, a stable gain and radiation pattern have been observed. The prototype has a measured isolation of ~30 dB. It should be mentioned that its cross-polarization level is more than −10 dB over a wide range of angles (−60° < θ < 60°). Finally, these advantages enable the proposed antenna to be potentially applied to the integrated design of 2G/3G/LTE base station antennas.A wideband low-profile crossed-dipole antenna with a novel AMC has been investigated. By introducing the AMC as antenna ground, the profile can be effectively decreased to 0.12λ


Multiple-input multiple-output (MIMO) technology has emerged as a highly promising solution for wireless communication, offering an opportunity to overcome the limitations of traffic capacity in high-speed broadband wireless network access. By utilizing multiple antennas at both the transmitting and receiving ends, the MIMO system enhances the efficiency and performance of wireless communication systems. This manuscript specifies a comprehensive review of MIMO antenna design approaches for fifth generation (5G) and beyond. With an introductory glimpse of cellular generation and the frequency spectrum for 5G, profound key enabling technologies for 5G mobile communication are presented. A detailed analysis of MIMO performance parameters in terms of envelope correlation coefficient (ECC), total active reflection coefficient (TARC), mean effective gain (MEG), and isolation is presented along with the advantages of MIMO technology over conventional SISO systems. MIMO is characterized and the performance is compared based on wideband/ultra-wideband, multiband/reconfigurable, circular polarized wideband/circular polarized ultra-wideband/circular polarized multiband, and reconfigurable categories. The design approaches of MIMO antennas for various 5G bands are discussed. It is subsequently enriched with the detailed studies of wideband (WB)/ultra-wideband (UWB), multiband, and circular polarized MIMO antennas with different design techniques. A good MIMO antenna system should be well decoupled among different ports to enhance its performance, and hence isolation among different ports is a crucial factor in designing high-performance MIMO antennas. A summary of design approaches with improved isolation is presented. The manuscript summarizes the various MIMO antenna design aspects for NR FR-1 (new radio frequency range) and NR FR-2, which will benefit researchers in the field of 5G and forthcoming cellular generations. Wireless and mobile applications have experienced significant growth, evolving from analog communication to digital communication. Modern antenna designs face challenges related to space constraints, interoperability, supporting multiple frequency bands, adhering to specific absorption rate (SAR) regulations, and accommodating hearing aid compatibility. Additionally, digital communication requires addressing issues such as variable data rates, high capacity, and scalable bandwidth at base stations and mobile devices. MIMO antenna behavior is characterized by several parameters. Far-field gain measures the intensity of radiation in the far-field region. Diversity gain quantifies the improvement in signal quality achieved through multiple antennas. The envelope correlation coefficient assesses the correlation between different antenna elements. The total active reflection coefficient measures reflections and losses in the antenna system. Mean effective gain evaluates the average gain in a particular direction. Next-generation mobile networks 5G, B5G) provide much faster connection and considerably higher data rates compared to fourth generation 4G) systems with better stability, higher channel capacity, more spectral efficiency, and lower energy consumption. International Telecommunication Union identifies new radio (NR) for International Mobile Telecommunication (IMT) NR FR-I (sub-6-GHz Band) with channels n78 (3.3–3.8 GHz), n-77 (3.3–3.8 GHz), n79 (4.4–5 GHz), FR-II (24.25 GHz to 52.6 GHz) with channels in FR-2 being n-258 (24.25–27.5 GHz), n-257 (26.5–29.5 GHz), n260 (37–40 GHz), and n261 (28.35 GHz) [G systemsG, B5G prThe massive volume of data traffic worldwide has increased manifold, so conventional antennas such as PIFA and monopoles cannot meet the demand. New multiple antenna technology with array and MIMO antenna is a promising technology to provide better channel capacity with additional bandwidth or transmission power. MIMO and m-MIMO are the next generation technology for mobile communication which groups multiple elements at the transmitter (Tx) and receiver (Rx) which provide better spectral efficiency, higher data rate, and channel capacity ,7. FigurEvolution of cellular technology 1G–5G:3GPP Release 15: This was the first release of the 5G standard, published in December 2017. It introduced the 5G New Radio (NR) technology and defined the initial specifications for 5G networks.3GPP Release 16: This is the second major release of the 5G standard, published in September 2020. It introduced enhancements, new features for 5G NR and the 5G core network, as well as specifications for new use cases and applications.3GPP Release 17: This is the next major release of the 5G standard, currently under development and expected to be published in 2022. It will continue to build on the capabilities and features introduced in previous releases, while also introducing new enhancements and use cases.3GPP Release 18: This is the next major release of the 5G standard, currently under development and expected to be published in 2023. It will further expand the capabilities and potential use cases for 5G technology, enabling new services and applications and enhancing the performance, security, and reliability of 5G networks. The cellular generation evolution along with the characteristics is summarized in First generation (1G) networks were analog and only supported voice calls. These networks were subject to interference and espionage because they employed frequency modulation (FM) to transmit signals. In 1979, Japan launched the first 1G network. Second generation (2G) networks were the first digital cellular networks that were developed in the early 1990s. To boost the capacity and quality of voice calling, these networks employed TDMA and CDMA technologies. Short messaging service (SMS) allows subscribers to send or receive text messages and was also deployed on 2G networks. Third generation (3G) networks were developed in the early 2000s and significantly improved network speed and data capacity. These networks enabled mobile internet access, video calling, and multimedia messaging by utilizing HSPA (High-Speed Packet Access) and WCDMA (Wideband Code-Division Multiple Access) technologies. Fourth generation (4G) networks, introduced in the late 2000s, provided faster network speeds and more data capacity than 3G networks. Long-term evolution (LTE) technology was utilized in these networks to enable faster download and upload rates, lower latency, and improved coverage. More sophisticated UE applications, such as online gaming, video streaming, and cloud computing, were also made possible by 4G networks. Fifth generation (5G) networks, which debuted in the 2010s, are the most recent iteration of cellular technology. The 5G networks employ modern radio technology including millimeter wave (mmWave) and massive MIMO to enable faster network speeds, reduced latency, and more data capacity than 4G networks. They also allow new applications such as virtual and augmented reality, smart cities, and self-driving cars. Major 3GPP (3rd generation partnership project) releases for the evolution of 5G from advanced LTE are given as follows :3GPP RelIn this survey, detailed analysis of the most widely used MIMO antenna configurations, wideband/ultrawideband MIMO antennas, multiband/reconfigurable MIMO antennas, and circularly polarized MIMO antennas is presented. A detailed comparison of the characteristics of MIMO antennas is also presented for various wideband, multiband, and circularly polarized MIMO antennas. The study highlights the different design approaches for efficient MIMO antennas for 5G systems. The compactness of handheld devices and the gadgets used in modern wireless communication pose significant challenges in terms of antenna size and mutual coupling reduction when placing multiple antennas in such scenarios. When multiple antennas are placed in close proximity, mutual coupling between them becomes a critical issue. The study highlights the different isolation or decoupling techniques used in the literature and their effectiveness in reducing mutual coupling among different ports in MIMO antennas with limitations and advantages. Firstly, the survey highlights the several techniques to design wideband/ultrawideband antennas and presents a comparative analysis based on their performance parameters such as gain efficiency, isolation, and diversity parameters of MIMO antennas. Secondly, multiband/reconfigurable antenna approaches are discussed where reconfigurability is achieved using switching action based on PIN diode and multiband using characteristic mode analysis, slots, defective ground structure, partial ground plane, or EBG (electronic bandgap structure) or other periodic structures such as FSS (frequency selective surfaces). Finally, the design approaches of the circular polarized MIMO antennas for LHCP/RHCP or bidirectional or with the polarization diversity are discussed in detail.The introduction part in In the context of 5G, the term “key enablers” refers to the fundamental technologies or components that are essential for the successful establishment and functioning of 5G networks ,11,12. TMillimeter-wave (mmWave)  technoloAnother issue is that mmWave signals are more susceptible to interference from other wireless signals as well as meteorological conditions such as rain and fog. To mitigate these issues, 5G networks that use mmWave technology use advanced signal processing techniques and beamforming to focus the signals in specific directions, which improves the quality of the signal and reduces interference. Despite these challenges, mmWave technology offers significant benefits for 5G networks, including faster data transfer rates, lower latency, and increased capacity. These benefits are particularly important for applications that require high bandwidth, such as VR , AR , and HD video streaming.m-MIMO technologies are another key technology for 5G cellular communication. It makes use of multiple antennas for the transmission and reception of signals simultaneously, which increases the network’s capacity and coverage. SISO, SIMO, or MISO has also been employed for the transmission and reception of signals in a traditional wireless communication system. However, with Massive MIMO technology, multiple antenna-elements are used on both sides of the transmitter and receiver system. The 16T × 16R MIMO antenna array is shown in Massive MIMO technology works by using complex signal processing algorithms to separate the different signals that are being transmitted and received by the multiple antennas. This allows telecommunication companies or regulatory bodies to efficiently use the existing spectrum and reduces interference between different signals. Massive MIMO technology not only boosts capacity and coverage but also enhances the quality of the wireless signal.With the advancement of networks and the growing need for data traffic, deploying small cells has emerged as a viable solution. These small, low-power wireless access points, operating within the licensed spectrum and managed by operators, offer improved cellular coverage and capacity. They are particularly beneficial in addressing coverage gaps, maintaining service quality, and efficiently utilizing spectrum resources. Small cells address this issue by providing additional coverage and capacity in areas where the large cell towers are not effective. Small cells can be of micro, macro, femto, or metro type. In urban areas, micro and metro type small cells offer coverage up to a few hundred meters. Pico cells provide coverage within a few tens of meters, both indoors and outdoors, primarily in public areas such as shopping malls, airports, and railway stations. Femtocells are mainly utilized in residential areas, covering a range of a few tens of meters.These small cells are installed on streetlights, utility poles, and other existing infrastructure in urban environments using a large number of access points (APs). By using small cells, 5G wireless networks can provide improved coverage and capacity in dense urban environments, which is essential for many applications such as smart cities, autonomous vehicles, and IoT devices. There are some challenges with femtocells and microcells such as management of the resources through scheduling at the edge of cell boundary, static and dynamic spectrum allocation, and frequent handover in some scenarios ,16.Network slicing is another feature of a 5G wireless network that allows many virtual networks to be formed within a single physical network, enabling telecom operators to deliver customized services to users as per the scenario shown in 5G and B5G make use of cloud computing, which has another advantage for wireless communication. It refers to delivering computing services over the cloud, including servers, storage, applications, and other resources, which can be accessed remotely by users and devices. In a 5G network, cloud computing provides numerous services and applications to users and devices, including edge computing, AI, and IoT applications. Cloud computing enables these services and applications to be delivered in a scalable, efficient, and cost-effective manner, which is essential for supporting the massive data volumes and high-performance requirements of 5G wireless networks. Cloud computing also enables AI and ML algorithms to be run on large datasets in a scalable and cost-effective manner. Machine learning provides numerous benefits, such as its capacity to analyze enormous datasets and detect patterns and trends ,20. ThisThis refers to the creation of virtual resources, such as servers, storage, and networks, that can be accessed and managed independently of the physical resources on which they are based. In a 5G network, virtualization is used to create virtualized network functions (VNFs) and virtualized network elements (VNEs), which enable operators to provide different types of services and applications in a scalable and flexible manner. Virtualization allows network functions to be run on standard hardware, rather than specialized hardware, which can reduce costs and improve scalability. Virtualization in a 5G network can support network slicing which is a key advantage. Network slicing involves creating multiple virtual networks within a single physical network, each with its own set of resources and characteristics, to support different types of services and applications. Operators can allocate resources to users on dynamic bases with a virtualization function for different services and applications in real-time, based on their changing requirements. This enables the network to be more efficient and responsive to changing traffic patterns, which can improve performance and reduce costs.Edge computing-oriented communications have emerged as promising technologies for enabling 5G/6G advancements. The rapid growth of smart devices and data traffic has driven operators to explore sustainable alternatives, such as cloud computing and virtualization, for deploying numerous base stations. Cloud-RAN (C-RAN) is an innovative RAN technology that leverages virtualization concepts, offering on-demand access to scalable computing resources from a shared pool ,20. It rCarrier aggregation involves the combination of multiple frequency bands to create a wider frequency band, which can provide higher data rates and better performance ,22. ThisThe MIMO diversity parameters, including the envelope correlation coefficient (ECC), total active reflection coefficient (TARC), channel capacity, mean effective gain (MEG), and spectral efficiency play crucial roles in the performance and effectiveness of MIMO antennas. These parameters collectively contribute to the performance, reliability, and efficiency of MIMO antennas. By optimizing these parameters, MIMO systems can achieve higher data rates, improved signal quality, enhanced system capacity, and better utilization of available wireless resources, ultimately enabling advanced wireless communication applications.In MIMO systems, evaluating the coupling between radiating elements is crucial, and ECC serves as a vital parameter for this purpose. Unlike isolation parameters, ECC considers return-loss of all ports and isolation among different ports to characterize complete antenna mutual coupling. The recommended value of ECC by the ITU should be less than or equal to 0.5 for mobile communication systems. Better performance in MIMO systems is indicated by a low ECC value, which signifies reduced coupling between radiating elements. Conversely, a higher ECC value can have an adverse effect. ECC for higher radiation efficiency greater than 90% can be obtained directly from the s-parameter and given as ,24:(1)|ρTo calculate ECC for an antenna with radiation efficiency below 90% involves the far-field parameters of the radiating antenna .(2)ρECCith port and ith port and TARC is a parameter of the MIMO antenna to validate the scattering parameters (s-parameters) for diversity performance. TARC employs both random signals and phase angles for diagonal and adjacent antenna ports to determine the behavior of s-parameters such as s11, s12, and s13 for particular phase combinations between the ports. TARC is calculated using the incident vector ai and reflected vector bi, which is independent and identically distributed Gaussian random variables. TARC can be calculated by ,24:(3)Γxgiven by :(4)[y1y2By solving the given scattering matrix for the scattering/reflected parameter, TARC can be obtained as :(5)Γxt=|x/Rx block diagram with MIMO channel is shown in Compared to SISO antenna systems, MIMO antennas exhibit higher channel capacity, which is a crucial performance parameter as given by ,26,27. TtB is the available total bandwidth and C is the Shannon channel capacity. The channel matrix “H” in the MIMO system is expressed based on the number of transmitter and receiver antennas, denoted as “tm” and “rm”, respectively [As per Shannon capacity theorem, the capacity for the SISO system is given as :(6)C=Bt ectively .(7)H=mty(t) is the received signal vector of s(t) is transmitter signal vector of n(t) spatial-temporal white noise with zero mean and variance s(k) is given as: Let given as :(8)y(t)=Case 1: Let the wireless channel be deterministic and known to the receiver, then the capacity of the MIMO system is given as :(9)C=B lCase 2: when the transmitter does not know the channel, then the s vector may be chosen as ystem is :(10)C=B∑ HHH=HHH :(11)C=B MEG refers to the combined gain of all the elements in the MIMO system, and it is typically expressed in decibels (dB). Mean effective gain is a measure of the effective gain of an antenna in a multiple-input multiple-output wireless communication network. MEG takes into account the antenna efficiency, the power patterns of the antennas, and the spatial correlation of multiple antennas used in the MIMO system .(12)MEGThe above equation requires a 3D radiation pattern of user equipment but the calculation of MEG using a 3D radiation pattern is tricky; therefore, using a 2D radiation pattern for the calculation of MEG is participable and is given in the following equation :(13)MEG=Other equations for MEG using the s-parameter can be ,29:(14)MIt is a measure of the amount of data that can be transmitted over a radio spectrum. It is generally expressed in bits per second per hertz (bps/Hz). Spectral efficiency (bits/s/Hz) is defined as han SISO .The growing range of mobile applications has led to a demand for Gigabit data rates to cater to users with different mobility levels, including both low and high-mobility scenarios. To address this requirement, traditional single antennas in mobile devices are being replaced with MIMO antennas. By implementing MIMO technology, mobile devices can deliver enhanced quality of service, offering uninterrupted signaling, high data rates, increased capacity, and improved spectral efficiency. Some of the advantages are listed below.MIMO technology allows for higher data rates compared to traditional single-input single-output systems, as multiple data streams can be transmitted simultaneously over the same frequency band. As the number of MIMO layers increases, the overall throughput of the system also increases.MIMO technology helps to improve signal quality by reducing the effects of fading, interference, and noise. As conventional SISO (single input single output), a single stream of data will be transmitted between transmitter and receiver which results in more interference and fading effects at the coverage boundary due to the large beamwidth of base station antennas shown in MIMO technology can extend the range and coverage of wireless networks by improving link quality and reducing the likelihood of signal dropouts. MIMO technology enables better spectral efficiency which allows more effective use of the available radio spectrum. This is achieved by transmitting or receiving multiple data streams simultaneously.MIMO technology is retrograde compatible with existing wireless standards, which means that it can be easily integrated into existing wireless networks without any major changes in the infrastructure.This section discusses various MIMO antenna designs such as wideband, multi-band, and circular polarized antenna configurations for FR-1 and FR-2 bands. These designs aim to achieve wide frequency coverage, support multiple frequency bands, and enable efficient circular polarization to meet the diverse requirements of wireless communication systems in these frequency ranges as shown in Wideband MIMO antennas are designed to operate across a broad frequency range, typically spanning multiple frequency bands within FR-1 and FR-2. These antennas employ various techniques to achieve wide frequency coverage, such as broadband feeding networks and radiating elements. Wideband MIMO antennas are capable of supporting multiple frequency bands simultaneously, providing enhanced spectral efficiency and compatibility with different wireless communication standards. The categorization of wideband MIMO antenna for sub-6GHz band and mmWave are shown in −6), diversity gain of 10 dB, and CCL of 0.005 bps/Hz were obtained. This study [In article , MIMO anis study  describeis study  has effiis study , while tis study  with twois study  for mmWais study ,36. Annuis study  4-port Mis study  was presis study  presenteis study  introducis study  consistsIn this study , the autThe study  introducReconfigurable/Multiband MIMO antennas are designed to support specific frequency bands. These antennas incorporate radiating elements or structures optimized for each desired frequency band. By utilizing frequency-selective elements, such as bandpass filters or resonant structures, multiband MIMO antennas can efficiently transmit and receive signals in each specific band. This design approach offers flexibility and compatibility with various network deployments and user equipment that may operate in different frequency bands as shown in The study  presenteThe study  describeComplimentary split ring resonator (CSRR)-based compact four port MIMO MSA in  for wireThe study  presenteIn this study , a quadbLinearly polarized antennas used in line-of-sight communication can receive signals with varying power levels. The antenna that receives the weakest signal sets the upper limit for diversity gain and subsequently affects the signal-to-noise ratio (SNR). Additionally, polarization mismatch can lead to insufficient signal gains for highly isolated antennas in both indoor and outdoor environments. However, in recent years, there has been significant research and industrial progress highlighting the importance of circularly polarized (CP) antennas in wireless applications. CP antennas can evenly distribute signal powers among receiving antennas, effectively addressing the issue of polarization mismatch. CP-MIMO (multiple-input multiple-output) antennas improve data rates, capacity, and diversity gain. Some of the circular polarization MIMO antennae with different techniques are listed below in The study in  presenteIn this section, some of the major issues and techniques of designing MIMO WB/UWB, multiband, and CP antennas are considered and compared according to their performance. This comparison provides a summary of In MIMO antennas, there are several challenges to design and integrate in the real environment. The major challenge in MIMO is mutual coupling which reduces the performance of the antenna. Closely spaced antennas give rise to electromagnetic coupling among different antenna ports, thus resulting in degraded performance. Apart from the mutual coupling, the size of the MIMO antenna in the perspective of the portable devices is also a concern to take care of carefully. Multiple antennas require more RF chains along with each antenna element, so the size and cost of the antenna are increased. Thus, techniques such as polarization diversity can be effective in such situations which can reduce the size and cost of the system to some extent. Thus, the researcher has to address different diversity in a single MIMO system carefully to achieve optimal performance. Some of the design challenges are discussed below.In MIMO antennas, multiple antennas at the transmitter and receiver sides are closely packed so resulting in mutual couplings among antenna elements. When multiple antennas are placed in close proximity, they tend to couple electromagnetic energy with each other, which can affect the performance of the MIMO antenna. Coupling can affect radiation patterns and degrade the isolation between antenna elements. There are various methods suggested in the literature to reduce mutual coupling and enhance the isolation among different ports. Parasitic elements, neutralization lines, slots/stubs, decoupling structures, defective ground structures, slot etching, metamaterials, unit cells, etc. are the most widely used isolation techniques ,88,89,90Meeting the growing need for increased mobile data volume necessitates enhanced capacities in radio mobile networks. While network densification and the integration of new frequencies are potential solutions, incorporating higher-order MIMO capabilities into existing radio networks presents an opportunity to significantly enhance peak data rates and augment overall network capacity. In conventional 2 × 2 MIMO networks, cross-polarized antennas are commonly utilized. To introduce additional, independent antennas into the system , a second cross-polar antenna can be employed . To ensuIn practice, large antenna spacings are often required to achieve significant multiplexing or diversity gain. The use of dual-polarized antennas (polarization diversity) is a promising cost- and space-effective alternative, where two spatially separated uni-polarized antennas are replaced by a single antenna structure employing orthogonal polarizations . This ca5G wireless network operates on the frequency bands sub 6 GHz and mmWave for 5G communication. Both Sub 6 and mmWave band have their pros and cons. The mmWave technology provides a higher data rate due to the large bandwidth availability but low coverage area because of more attenuation at high frequencies. The sub-6 GHz band has low attenuation loss with greater coverage area and lower data rate due to the limited bandwidth availability . Thus, iA comprehensive review of MIMO antenna design approaches has been discussed in this paper. WB/UWB characteristics were achieved through different modifications of radiating patch, ground plane and feeding network. H-P shaped, E-L shaped, annular ring, DGS, partial ground plane, and metamaterial structure were employed to achieve wideband or ultra-wideband properties. Multiband MIMO antennas can be achieved through different aspects such as characteristic mode theory, stubs and slots on radiating patch, EBG structure, SRR or CSRR, and reconfigurable patch antenna. Moreover, the CP-MIMO antenna can be designed by optimizing the radiating patch, ground plane, and feed network through different techniques. It was observed that using the spiral slot on radiating patches, circular patches, tapered edges of patches, or diagonal slots on patches leads to circular polarization. Quarter phase delay lines, plasma boxes, circular rings or defects in the ground plane, split ring resonator, or complementary split ring resonator are other promising design techniques to obtain a circularly polarized antenna. Apart from MIMO antenna design techniques for WB/UWB, multiband and CP-MIMO isolation among different ports have been the utmost priority. In this study, different MIMO configurations with decoupling structures were also presented. Some of the decoupling networks or structures are neutralization line, meander line, isolation improvement based on SRR or CSRR structures, shorting pin, parasitic elements, slots with DGS, and feeding network, which are promising techniques to reduce the isolation among the ports, leading to the design of high-performance MIMO antennas. Thus, in this review paper, different design aspects of MIMO antenna for NR FR-1 and FR-2 were studied, which will be helpful for researchers to further fulfil the demand for high data rate in 5G and B5G cellular generation.


In this paper, an absorbing material on a button antenna is proposed for pedestrian-to-vehicle (P2V) communication, which provides safety service to road workers on the highway or in a road environment. The button antenna is small in size and is easy to carry for carriers. This antenna is fabricated and tested in an anechoic chamber; it can achieve a maximum gain of 5.5 dBi and an absorption of 92% at 7.6 GHz. The maximum distance of measurement between the absorbing material of the button antenna and the test antenna is less than 150 m. The advantage of the button antenna is that the absorption surface is used in the radiation layer of the antenna so that the antenna can improve the radiation direction and gain. The absorption unit size is 15 × 15 × 5 mm The cooperative intelligent transport systems (C-ITS) pilot deployment project, which has the objective of developing and experimenting with innovative road CITS solutions, offers pedestrian-to-vehicle P2V) communication systems for vulnerable road user (VRU) protection V communi,5,6,7,8.3 and a measured gain of 5.5 dBi. This absorbing button antenna is suitable for short-distance communication. The structure of this paper is as follows. In the next section, the overall structure of the button antenna and its material composition are introduced. In In this paper, an absorbing material for a button antenna is proposed. It mainly solves two problems of an antenna: antenna miniaturization and high gain directional radiation. The absorption rate of the button antenna can reach 92% at 7.6 GHz. It has an overall size of 15 × 15 × 5 mm3, where the grounding and feed isolation aperture is 2 mm and the coaxial feed diameter of the antenna is 1 mm. The antenna is composed of two substrates of glass fiber epoxy (FR-4) material. The FR-4 material has the advantages of a simple structure, easy fabrication, and good physical characteristics, meaning that the antenna radiation is not constrained by its own shape, allowing it to realize a stability of radiation. The permittivity of these substrates is 4.4, with a tangential loss of 0.027 and a thickness of 1.5 mm. A coaxial feed link is used to connect the parasitic patch and radiation patch to reduce coupling and impedance matching. The parasitic patch makes the antenna reach its maximum gain with a size of 13 × 13 mm2.As shown in This section mainly designs and analyzes the absorption material properties of the button antenna. Its main innovation comes from ,31. Firsn), which are approximately equal to zero by periodic electrical boundary (PEC) and periodic magnetic boundary (PMC) simulation results, which is obtained using Equations ..ε), magn μ = n×z .A,,5), bothEquation . The resa height .(6)Q∝DThe change in the Q value can affect the gain of the whole antenna. Therefore, to improve the gain of the CRO antenna, we should first analyze the factors in the CRO structure that can affect the Q value, determine which factors have the greatest influence on Q value, and finally adopt the methods that further improve the Q value to increase the antenna gain. As shown in Equation  is estabEquation  is estabEquation  is substEquation  to obtaiEquation ; in thisThe mpedance .(8)Zri∣h is the height of the coil; we are assuming that it is a constant. i = 1, 2, 3) is the width of coil [i = 1, 2, 3) is the coupling distance parameter of the coil, whose corresponding reactance is i = 1, 2, 3). The effect of the coil area on the capacitance is ignored [The  of coil .(9)Zrea ignored .(12)ZimQ is the quality factor and The main contents of this section are as follows: First, we analyze the improvement of the gain of the button antenna by quality factor Q. Second, the equivalent circuit method is used to analyze the embedded microstrip lines. Finally, the effect of its quality factor and CRW structure on the gain of the button antenna is analyzed. As seen in the previous section, the largest change in the CRO structure is the quality factor Q, as shown in Equation . In thisEquation , Q is ren 0.35λ0 . Q is th(1)The relationship between quations –17);;T1 and t(2)The impedance Equation  of the r(3)Taking the derivative of Equation , EquatioAs shown in After calculation, the following conclusion can be drawn: quations –23) and andT1 ise length ,41.(16)The constant ,43.(17)mpedance ,45.(22)To further improve the antenna gain, microstrip lines are continuously embedded. As shown in 2. All of the material parameters of the tissue were obtained from the values available in the CST Studio human tissues library. A 5 mm air gap was set between the antenna and the surface of the skin to mimic any worn clothes. An R&S microwave signal generator was used to test the In this section, the performance of the button antenna is evaluated on the human body. The absorptivity, S-parameters, efficiency, and radiation pattern are analyzed together with the SAR values. The scenario of the numerical model is shown in For wearable applications, the SAR value is a critical parameter. The numerical SAR distributions of the proposed antennas are shown in As shown in An absorbing material on a button antenna for P2V communication was proposed, fabricated, and measured, which provides safety service to road workers on highways or in a road environment. The maximum distance of measurement between the absorbing material of the button antenna and the test antenna is less than 150 m, which is a safe distance for traffic. This antenna can achieve a maximum gain of 5.5 dBi and absorption of 92% at 7.6 GHz. Compared with other similar antennas in


In this paper, a low-cost resin-coated commercial-photo-paper substrate is used to design a printed reconfigurable multiband antenna. The two PIN diodes are used mainly to redistribute the surface current that provides reconfigurable properties to the proposed antenna. The antenna size of 40 mm × 40 mm × 0.44 mm with a partial ground, covers wireless and mobile bands ranging from 1.91 GHz to 6.75 GHz. The parametric analysis is performed to achieve optimized design parameters of the antenna. The U-shaped and C-shaped emitters are meant to function at 2.4 GHz and 5.9 GHz, respectively, while the primary emitter is designed to operate at 3.5 GHz. The proposed antenna achieved peak gain and radiation efficiency of 3.4 dBi and 90%, respectively. Simulated and measured results of the reflection coefficient, radiation pattern, gain, and efficiency show that the antenna design is in favorable agreement. Since the proposed antenna achieved wideband (1.91–6.75 GHz) using PIN diode configuration, using this technique the need for numerous electronic components to provide multiband frequency is avoided. The rapid growth of technology requires significant innovations to upgrade the present devices to meet the demands of present and new wireless communications and Internet of Things (IoT) applications. An antenna plays a vital role in wireless communication, so with advancement in technology the antenna needs to be modified. Antenna designs with fixed characteristics can be replaced by evolvable antennas that provide multi-band and reconfigurable characteristics that can be used for many applications . Small aIf the above mentioned substrates are replaced with a paper substrate, then the cost is reduced by a factor of ten . BesidesIn the present study, a low-cost adhesive copper-on-paper substrate is constructed as a reconfigurable antenna that can be used for IoT applications, wireless communication, and mobile bands. The antenna’s main radiator is made up of a variety of smaller radiators that each support a distinct frequency band. These shapes are designed to minimize the overall size of the antenna and to have a multiple-band response. The copper material as the radiating element and the PIN diode as the switching circuits are printed on the paper substrate, which makes it convenient and smooth for the integration of antenna into the IoT device. The antenna is designed on a paper substrate with a thickness of 0.44 mm, a dielectric constant of 3.2, and a loss tangent of 0.05 for multiple applications, and providing triple-band frequency ranges 1.91–2.68 GHz, 3.33–3.75 GHz, and 5.55–6.75 GHz. The frequency band changes with the change in switching state of the PIN diodes. By altering their switching conditions, the PIN diodes found in the antenna construction contribute significantly to the achievement of various frequency bands. The advantage of the proposed design is using photo paper as a substrate. The realization of the multi-band antenna on a low-cost paper substrate using adhesive copper has the advantages of a small size, low profile, and simple configuration. The low profile of the antenna makes it a promising candidate for future compact and slim wireless devices.The suggested microstrip antenna is depicted in The proposed antenna, which lacks a ground plane directly beneath the substrate, presents different design considerations compared to, for instance, a patch antenna with a ground plane directly beneath it. In this context, the chosen antenna design is significantly influenced by the choice of substrate. Altering the substrate material would have a substantial impact on the antenna’s performance.Changing the substrate can affect the antenna in several ways, including the following: Size and Dimensions: The physical dimensions of the antenna, including the size and shape of the radiating element, are influenced by the substrate. Changing the substrate might require adjustments to the antenna’s physical design.Resonant frequency: The substrate material affects the antenna’s resonant frequency. A change in the substrate can shift the operating frequency of the antenna, which may or may not align with the intended frequency band.Operating bandwidth: The choice of substrate can affect the antenna’s bandwidth. A new substrate may widen or narrow the antenna’s operational bandwidth.Radiation pattern: The substrate influences the radiation pattern of the antenna. Different substrates can lead to variations in the antenna’s radiation characteristics, such as beamwidth and directivity.Efficiency: The substrate’s dielectric properties impact the antenna’s efficiency. A different substrate can lead to changes in radiation efficiency, which could be detrimental or beneficial depending on the application.So, the choice of substrate plays a crucial role in determining the antenna’s electrical and mechanical characteristics. When altering the substrate, careful consideration and possible redesign are necessary to maintain or improve the antenna’s performance in the desired application.S’) and a low value inductor (‘L’), form a simple RL series circuit for the ON state. It is equivalent to an RLC circuit in the OFF state because an inductor (L) is connected in parallel with a high-value resistor (RS) and a capacitor (CR). A DC bias voltage of +3 V and 0 V, respectively, can be used to turn “ON” and “OFF” the PIN diodes. The diodes utilized are SMP1345-040LF diodes from Skyworks Solutions Inc., which are practical and affordable. The diode has a resistance, inductance, and capacitance of 1 Ω, 045 nH, and 0.2 pF, respectively, in the ON state, and 3.3 kΩ and 0.2 pF, respectively, in the OFF state, according to the data sheet. The parametric study is then performed to optimize the design parameters of the proposed antenna and a simulation is performed using HFSS.In the parts that follow, copper foil has been utilized as a conductive medium for both simulation and fabrication. The optimized dimensions of the antenna are listed in Fabricating an antenna using two sheets of photo paper, each with a thickness of 0.22 mm, involves several steps. Below is the fabrication process:Step-1 The optimized antenna dimensions as mentioned in Step-2 The copper is subjected to wet etching. This process reveals the adhesive layer where the copper has been removed, while the opposite side remains protected by the original adhesive copper tape. In essence, the first two steps closely resemble standard photolithographic techniques. Then, the adhesive-backed copper foil is placed on a clean, flat surface with the adhesive side facing up. Carefully, the backing is peeled off the copper foil to expose the adhesive side.Step-3 A sacrificial layer is affixed to the copper side, after which the protective layer is removed. The sacrificial layer serves a crucial role in maintaining the relative distances among layout features, especially when they are not physically connected. This layer can be as simple as a sheet of paper or a plastic adhesive tape. In the former case, the exposed adhesive (where the copper has been removed) provides sufficient adhesion for attaching the sacrificial paper sheet. In the latter case, the adhesion of the sacrificial layer is deliberately chosen to be lower than that of the copper tape itself. The antenna and the ground plane of the antenna are printed on two sheets of photo papers, each with a thickness of 0.22 mm. Two sheets are used to help to reach a reasonable thickness (0.44 mm). Alignment marks have been implemented on the photo papers so that the two photo papers can be glued together with correct alignment to form a single antenna substrate.Step-4 The etched metal is transferred onto the hosting paper substrate, and ultimately, the sacrificial layer is detached. This final step also eliminates most of the exposed adhesive material, with the effect being more pronounced when a plastic adhesive tape is employed as the sacrificial layer. The SMA, PIN diodes, resistors, and capacitance are then mounted on the antenna using low-temperature solder pastes and epoxies.Step-5 The antenna’s performance is tested using the appropriate testing equipment.A parametric study of an antenna can be highly sensitive to physical layout variations due to the intricate relationship between the antenna’s design parameters and its performance characteristics. Here is how this sensitivity arises:Electromagnetic interactions: Antenna design parameters, such as the length, width, and spacing of elements, influence how electromagnetic waves interact with the antenna. Small changes in these dimensions can lead to significant variations in the antenna’s impedance, resonance frequency, and radiation pattern.Resonance effects: Antennas are typically designed to resonate at specific frequencies. Variations in physical dimensions can result in shifts in the resonant frequency, potentially causing the antenna to operate outside of the desired frequency band.Radiation pattern: The physical layout affects the radiation pattern of the antenna. Alterations in element size and spacing can lead to changes in the directionality, gain, and beamwidth of the antenna’s radiation pattern.Impedance matching: Antennas need to be impedance matched to the transmission line or circuit to ensure efficient power transfer. Physical-layout changes can impact the impedance, leading to mismatches and reduced performance.Material properties: The choice of substrate and materials also plays a role in antenna performance. Variations in substrate properties can affect the antenna’s efficiency, bandwidth, and radiation characteristics.Manufacturing tolerances: Real-world fabrication processes have tolerances and variations. Small discrepancies in the manufacturing of antenna elements can accumulate and lead to sensitivity to physical layout changes.g) and feed width (Wf).The parametric investigation of S11 has been carried out by altering the ground length  by alternating between the primary radiator and the C- and U-shaped radiators using two PIN diodes. The analysis of antenna bending was conducted due to the flexible substrate used in the proposed design. The antenna under consideration demonstrated a peak gain of 3.42 dBi and an efficiency exceeding 60%. As a result, this paper’s substrate antenna is well-suited for effective utilization in mobile bands and multiple wireless applications.


The ground plane and radiator of this antenna are adjusted in several ways to bring it within its operating constraints between the frequencies of 3.1 GHz and 10.6 GHz. This technique makes the antenna small and covers the entire ultra-wideband (UWB) frequency range. The NI USRP was used to test the proposed MIMO antenna to determine its real-time performance. Based on the computed results, we conclude that this proposed antenna has outstanding characteristics in terms of performance and is suitable for wireless ultra-wideband indoor communication and diversity utilization with a small size.A compact, four-element planar MIMO  antenna that operates in an ultra-wideband is presented for diversity application. The orthogonal position of the unit cells replicates the single antenna thrice, thereby decreasing mutual coupling. A UWB MIMO antenna measuring 35 × 35 × 1.6 mm UWB refers to an ultra-wideband with a frequency ranging from 3.1 to 10.6 GHz. The bandwidth of 7.5 GHz for UWB communications was authorized by the Federal Communications Commission (FCC) in 2002 for use in a variety of commercial applications . The antThe main and primary contribution of this paper is the thorough magnified presentation of four compact ultra-wide-bandwidth MIMO antennas with isolation between ports having more than 35 dB that satisfy the criteria and operates well between 3.1 and 10.6 GHZ. The rest of this work is structured as follows. The design process for a single antenna and four-element MIMO antennas are thoroughly described in The proposed unit-cell antenna, based on an FR4 substrate, has a microstrip feed. The FR4 substrate has a 4.3 relative permittivity  plane is constructed with a rectangle-shaped slot that is 7 × 16 The scattering characteristics (S11) of the antenna are shown in To create a multi-port antenna with good isolation, the single-cell antenna is to be duplicated and arranged such that it forms an orthogonal pattern. On a single plane, all radiating components are organized. The four-port antenna’s overall dimensions are 35 × 35 × 1.6 By performing parametric analysis and optimization, the proposed antenna is structured and developed using CST Microwave Studio Software. The proposed MIMO/Diversity antenna is measured using an Anritsu MS2703 Vector Network Analyzer.Four antennas that appear to be quite close to one another are included in the monopole ultra-wideband Multiple-In Multiple-Out antenna. As a result, interference from one antenna’s radiation with the others would occur.By building the redesigned ground structures, the mutual coupling is decreased, and identical antennas are positioned orthogonally. For the full bandwidth range, this antenna is designed such that it decreases mutual coupling to lower than −35 dB. The results of the S-Parameter simulation and measurement for the monopole ultra-wideband MIMO antenna are shown in Four antennas that appear to be quite close to one another are included in the correlation that exists between the radiating objects. This correlation is the most significant diversity characteristic of the Multiple-In Multiple-Out antenna. The degree of independence relating to the radiation patterns of two antennas is described with the help of ECC. Usually, the radiation patterns of the two antennas are completely not dependent on each other. The value of ECC must be 0; however, its real value must not be more than 0.5. The calculation of the envelope correlation coefficient is carried out by substituting the S-Parameter in Equation (2) ,20. ThroIn order to retain the dependency of the wireless communication system along with high-quality output, it is necessary to maintain the diversity gain of the monopole ultra-wideband Multiple-In Multiple-Out antenna at its maximum. Ideally, 10 dB is the best value. The diversity gain value for the suggested antenna can be derived using the formula in Equation (3) . We can ix denotes incident signals; iy denotes reflected signals. TARC represents the ratio of the incident power to the squared value of the reflected power. Equation (4) represents the TRAC ratio of the N port antenna.× 2 arrangement of the antenna is shown in Equation (5).The scattering matrix pattern of a 2 Every excitation signal’s phase in the Multiple-In Multiple-Out antenna is arbitrary. Before a signal reaches a receiver, the propagation environment helps to randomize the signal phases further. As a result, the MIMO channel signal is regarded as having an independent, identical distribution with a random phase. Equations (6) and (7) can be used to express reflected signals. The sum or difference of the Gaussian random variables produces the Gaussian values .(6)y1=SThus, TARC is explained in the following Equation (9).The return loss of the entire proposed MIMO antenna is known as TARC. TARC was first proposed to assess a multiport radiator’s performance. Because it takes into account mutual coupling, port matching, and the impact of the random phases of incoming signals into each antenna element, TARC has recently been found to be useful as a MIMO metric for antenna systems. This is because it describes the performance in a more realistic situation of a communications channel. TARC is the sole MIMO parameter that takes into account the unpredictable phases of incoming signals, which can have a significant impact on MIMO array behavior in certain circumstances. Over the whole working frequency band, TARC is less than −10 dB. The obtained TARC is shown in MEG1 and MEG2.The definition of MEG is the segregation of power received by an isotropic antenna with power obtained from a diversity antenna ,23. The MEG-1 and MEG-2 are identical due to the enhanced total performing capacity of the proposed radiator.The highest message rate at which a message may be sent across a communication channel without experiencing any losses is referred to as channel capacity loss. Equation (11)  can be uThe value of CCL value must be less than 0.4 bits/S/Hz in general. The proposed antenna’s simulated and measured E-plane and H-plane radiation patterns at 3.8 GHz frequency are illustrated in With the help of this pattern, it is possible to demonstrate how the designed MIMO antenna exemplifies pattern variety in the 3.8 GHz frequency range. The Port 1 and Port 3 patterns are moved 180 degrees in relation to one another, and Ports 2 and 4 are turned 180 degrees in relation to one another. The proposed antenna’s E-plane radiation pattern is shaped like a dumbbell, while the H-plane radiation pattern is omnidirectional ,26. A stThe investigation of the designed ultra-wideband MIMO compact antenna utilized the NI 2943R (USRP) and NI 802.11 framework in an indoor setting to confirm the proposed MIMO antenna’s real-time transmitting and receiving capabilities. The National Instruments (NI) Universal Software Radio Peripheral (USRP) is a technology-driven RF transceiver operated for software-defined radio R&D (SDR). For communications purposes, USRP NI transceivers are capable of transmitting and receiving radio frequency signals in a number of bands. The indoor setting is composed of an antenna feed system, two NI USRPs, and a received power monitor. For verification of real-time measurements, consideration should be given to signal reception power (RSRP) parameters ,32. The To test the MIMO antenna’s real-time performance, three alternative states are used.State 1: Radiators W, X, Y, and Z are considered to be the receivers, whereas radiators P, Q, R, and S are considered to be the transmitters. State 2: Antenna radiators P, Q, W, and X are considered transmitters, whereas radiators R, S, Y, and Z are considered receivers.State 3: The antenna radiators W, X, Y, and Z are considered to be transmitters, whereas P, Q, R, and S are considered to be receivers. Using the USRP 2943R, 2. The proposed MIMO antenna’s real-time short-range transmission and reception were tested in an indoor setting utilizing the NI 802.11 framework. With NI USRP, the proposed compact UWB MIMO antenna’s real-time performance was experimentally tested in a closed environment.The orthogonal array of the antenna elements seems to be the most practical way to reduce mutual interaction between ultra-wideband MIMO antennas, thus achieving compact dimensions. Successfully achieved mutual coupling of the suggested antenna has been below −35 dB. The 1.6 mm thick substrate was utilized to create a radiating antenna with a small footprint that is suited for diversity applications. The antenna’s dimensions are 35 × 35 mm