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Article

Compact Sub-6 GHz Four-Element Flexible Antenna for 5G Applications

by
Mahmoud A. Abdelghany
1,2,*,
Ahmed A. Ibrahim
2,3,
Hesham. A. Mohamed
4 and
Emad Tammam
2,3
1
Electrical Engineering Department, College of Engineering, Prince Sattam Bin Abdulaziz University, Wadi Addwasir 11991, Saudi Arabia
2
Electronics and Communications Engineering Department, Minia University, Minia 61519, Egypt
3
Communications and Computer Engineering Department, Nahda University, Benisuef 62764, Egypt
4
Electronics Research Institute, Microstrip Circuits Joseph Tito St, Huckstep, El Nozha, Cairo 11843, Egypt
*
Author to whom correspondence should be addressed.
Electronics 2024, 13(3), 537; https://doi.org/10.3390/electronics13030537
Submission received: 9 December 2023 / Revised: 31 December 2023 / Accepted: 4 January 2024 / Published: 29 January 2024
(This article belongs to the Special Issue Application and Design of Integrated Antennas in Wireless Communication)
Browse Figures
Versions Notes

Abstract

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

1. Introduction

With the increased demand for wireless services and the emerging 5G communications accompanied by the Internet of Things (IoT) concept, it is expected that a huge amount of data will be exchanged among the users of these technologies [1]. One of the main elements of communication systems that can be utilized to serve 5G requirements is the antenna. The antenna can be designed as a single element or multiple elements. Most antenna designs in the literature are single elements. However, single-element antennas have limited capabilities from the perspective of gain and bandwidth. Multiple-input multiple-output (MIMO) antenna systems have emerged as an effective means to fulfill the high-speed requirements of rapidly evolving communication systems. In the MIMO antenna configuration, some antenna elements are organized on the same substrate, while each element is fed through its own port. All these ports may be operated at the same carrier frequency, while each port is used to carry a part of the system data [2,3].
Many MIMO antenna designs with a variety of aspects can be found in the literature [4,5,6,7,8,9]. Two elements [10,11], four elements [5,12,13,14], six elements [15], etc., can be utilized in MIMO antenna designs. One of the most popular MIMO designs is the four-element MIMO system. A four-element MIMO antenna can be organized in linear or rectangular configurations. In one of the distinguished MIMO designs, the authors of [12] proposed a single circular patch that can be utilized as a single radiator that serves four ports, i.e., the four-element MIMO antenna was designed with a single radiator. In general, the MIMO antenna system is constructed such that each port can be a single-element antenna or an array of antennas. In [16], a MIMO system of two ports was presented, with each port being a four-antenna array fed by a corporate feeding network. Recently, the concept of a massive MIMO system has been adopted for MIMO antennas with a very large number of elements to represent an important component of future wireless technology [17,18,19]. Regarding the operating frequency band, some MIMO designs have considered lower frequency bands, i.e., sub-1 GHz [20,21]; however, some frequency bands—due to their importance—have attained more attention from researchers, such as those using sub-6 GHz [16,22,23]. In [23], for example, a four-port antenna was proposed, such that the four ports were placed at the four corners of a flexible substrate with a common ground plane in the center between them. Each port antenna was designed as four octagonal rings between two conducting layers of a T shape. The antenna structure was equipped with L-shaped and E-shaped conducting structures, which were optimized to operate the antenna over a wide frequency band, i.e., 2.37–5.85 GHz. In addition to a single-band MIMO antenna, multiband MIMO antennas can also be designed [24,25]. In [26], a reconfigurable dual-band antenna that worked from 1.3 to 1.8 GHz and 1.8 to 2.6 GHz was investigated. Triple-band MIMO systems can be found in [27,28]. Additionally, ultra-wideband (UWB) MIMO antennas were introduced in [29,30].
The coupling between ports is considered an important aspect of the MIMO system. Mutual coupling between the different ports has to be maintained at the lowest level possible. The spacing between the different antenna elements has to be increased to at least 0.5 λ to minimize the mutual coupling [31]. Hence, a tradeoff between the mutual coupling reduction and the size miniaturization of the MIMO antenna is imposed. Electromagnetic bandgap (EBG) structures [32], metamaterial structures [33], and defected ground structures (DGSs) [34] are utilized to enhance the isolation between ports. On the other hand, some designs have made use of the MIMO configuration itself to improve the isolation between the MIMO ports [6,35].
As future wireless devices are intended to be portable with lightweight, low-profile, and flexible characteristics, using a flexible substrate introduces valuable advantages to the designs of MIMO antenna systems, such as small size, low weight, and flexibility of use [36]. However, adding the antenna on a thin substrate requires some effort [37]. In addition, conducting experimental measurements of a flexible MIMO antenna is not an easy job. Although a large number of MIMO antenna designs exist in the literature, few works have discussed a flexible substrate [38].
In this design, a four-port flexible antenna for 5G applications is introduced. The single element was designed as a monopole radiator linked with a coplanar waveguide (CPW) line and printed on a flexible substrate. The single element was tested in flat and bent substrate positions. Then, four copies of the designed antenna element were organized on a single flexible substrate, such that the four antenna elements were mutually orthogonal to each other. Such a configuration of a four-port MIMO antenna was chosen to reduce the mutual coupling between ports [32].
The design of a single-element flexible antenna is described in Section 2. Section 3 discusses the MIMO antenna. The MIMO operation of the proposed antenna is validated in Section 4, followed by the conclusion.

2. Single-Element Flexible Antenna

2.1. Antenna Description

As shown in Figure 1, a two-arm monopole radiator fed by a CPW feed line was proposed to shape the antenna. A 0.13 mm thickness of a flexible ROGERS3003 substrate of εr = 3 and tan δ = 0.0013 was utilized in this design. The antenna’s configuration dimensions are illustrated in Figure 1a. Figure 1b,c show the antenna bent around the y-axis and x-axis, respectively, with a radius of curvature R.

2.2. Simulation and Measurement Results

The CST software was applied through the simulation process. The antenna design steps are illustrated in Figure 2. The antenna design started with a C-shaped radiator to operate at 2.85 GHz with S11 ≤ −10 extended from 2.8 GHz to 2.85 GHz. Then, step 2 was introduced by increasing the length of the upper part of the left-hand arm, as shown in Figure 2. The antenna worked at 2.45 GHz with S11 ≤ −10 extended from 2.38 GHz to 2.58 GHz. Additionally, step 3 was presented by adding an inverted C-shaped in the second arm to reduce the frequency band to 4 GHz with S11 ≤ −10 extended from 3.58 GHz to 4.37 GHz. Finally, to tune the desired antenna to operate at 3.5 GHz, step 4 (proposed) was introduced, as illustrated in Figure 2. A copy of the left-hand arm was added to the right-hand section, resulting in the proposed symmetrical structure that operates at 3.5 GHz with S11 ≤ −10 extended from 3.2 GHz to 3.9 GHz.
To investigate the operation of the proposed antenna, a parametric analysis was carried out on the flexible single-element antenna, as illustrated in Figure 3. The effect of the length of (Y1) on the S11 parameter is shown in Figure 3a. It was noticed that the antenna’s operation was shifted from 3.8 GHz to 3.7 GHz when (Y1) was changed from 8 mm to 9 mm. With Y1 = 10 mm, the antenna operates at 3.55 GHz. Additionally, the effect of the length of (X1) on the S11 parameter is illustrated in Figure 3b. The antenna’s operation was shifted from 3.82 GHz to 3.6 GHz when (X1) was changed from 7 mm to 9 mm. With X1 = 11 mm, the antenna operated at 3.55 GHz. Also, the effect of the length of (Y2) on the S11 parameter is shown in Figure 3c. The antenna’s operation was shifted from 3.96 GHz to 3.72 GHz when (Y2) changed from 5 mm to 7 mm. With Y2 = 9 mm, the antenna operated at 3.55 GHz. Finally, the effect of the ground’s length (Lg) on the S11 parameter is presented in Figure 3d. It was seen that the antenna’s operation was shifted from 2.91 GHz to 3.24 GHz (with bad matching) when (Lg) changed from 7.75 mm to 8.75 mm. With Lg = 9.75 mm, the antenna operated at 3.55 GHz.
The fabricated antenna prototype is shown in Figure 4a. The Rohde and Schwarz ZVA67 was applied in the process. The measurement setup is shown in Figure 4b,c of the antenna attached to the test feature kit for measuring. Figure 5 illustrates the return loss outcomes extracted from the simulation and measurement. The simulated antenna outcomes extended from 3.2 GHz to 3.9 GHz, while the tested outcomes extended from 3.28 GHz to 3.85 GHz, with a good trend between the two outcomes. The return loss outcomes at different cases of the radius of curvature are illustrated in Figure 6. The antenna was still properly matched over the same frequency band of the flat position, i.e., 3.2 GHz to 3.9 GHz. The results of the current distribution at 3.5 GHz, which is the peak resonance frequency, are displayed in Figure 7. It can be observed that the current is smoothly distributed over the two arms of the antenna.

3. Proposed Flexible MIMO Antenna

3.1. The Flexible MIMO Antenna Configuration

After designing and performing the test of the single-element antenna, four replicas of the designed antenna were printed on a single flexible substrate to constitute a four-port antenna that can be utilized in MIMO communication systems. The four antenna elements were organized on the same substrate, as shown in Figure 8. Figure 8a illustrates the configuration dimensions. The overall size of the four-port MIMO antenna is 66 × 66 × 0.13 mm3, and the maximum spacing between each two adjacent elements is 0.16λo. Figure 8b shows the four-port flexible MIMO antenna while it was curved around the y-axis with R = 50 mm.
The proposed four-element flexible antenna was simulated, fabricated, and experimentally tested. Figure 9a illustrates the fabricated four-port antenna, while Figure 9b shows the measurement setup of the bent antenna (R = 50 mm). A curved foam surface was used to support the flexible four-port antenna during the measurement process.

3.2. S-Parameters and Current Distribution Analysis

The simulation results were validated by the experimental measurements. The simulated and measured return loss at port 1 (S11) of the MIMO antenna in a flat position is shown in Figure 10. The antenna was matched from 3.2 GHz to 4.12 GHz, with a deep level of −24 dB at the peak resonance frequency. The measurement setup of the flat MIMO antenna also appears in Figure 10, while the four-port MIMO antenna was supported by a foam layer with a 1.03 dielectric constant to facilitate the handling of the flexible substrate during measurement. To investigate the isolation characteristics between the different antenna elements, insertion losses between port 1 and the other three ports were tested for the flat antenna. Figure 11 displays the simulation and the measurements of the S21, S31, and S41. Looking into the S-parameters at the frequency band from 3.2 GHz to 4.12 GHz, it can be observed that S21 and S41 fluctuate around −35 dB and −30 dB, respectively; however, S31 records a higher level of coupling of about −20 dB. This was an expected result because antenna elements 2 and 4 were in an orthogonal direction with respect to antenna element 1, while antenna element 3 was in a collinear direction with respect to antenna element 1.
To validate the simulated S-parameters of the suggested antenna in the bending configuration, the same procedure followed in Section 2 was used here. The fabricated antenna was mounted to a curved foam sheet with R = 50 mm, as displayed in Figure 12. The measured S11 is plotted against the simulated one in Figure 12. The antenna worked from 3.2–3.98 GHz, with a minimum of −33 dB at 3.7 GHz, which is approximately the same outcome as the flat antenna.
The insertion losses between port 1 and the other three ports of the antenna for the bent configuration were tested and plotted in Figure 13. Similar to the case of the flat MIMO, it can be observed, over the matched frequency band, that S21 and S41 fluctuate around −30 dB; however, S31 fluctuates between −20 dB and −30 dB.
The simulated current distribution of the flexible MIMO antenna, while only one port was excited, is shown in Figure 14. Figure 14a shows the effect of feeding port 1 of the flat antenna. The induced current in the neighboring antenna elements was used as an indicator of the amount of power coupling and then the isolation between elements. Figure 14b illustrates the current distribution of the bent antenna while only port 1 was excited.

3.3. Radiation Characteristics of MIMO Antenna

Simulated 3D radiation patterns of the flat and bent four-port flexible MIMO antennas at 3.5 GHz are shown in Figure 15 and Figure 16, respectively. Figure 15a shows the simulated 3D radiation pattern of the flat MIMO antenna of the four ports, while each port is individually fed with each one of the other three ports matched to 50 Ω. The plan view of the 3D patterns is shown. The radiation pattern of the antenna elements is shown in Figure 15. The same radiation pattern was obtained for the four antenna elements, except that the four patterns were orthogonal to each other according to the orthogonality of the four antennas with respect to each other. The radiation pattern of the bent MIMO antenna is shown in Figure 16. Figure 16 shows the 3D radiation patterns of the four ports, while each port was individually fed with each one of the other three ports matched to 50 Ω. Looking into the two figures, i.e., Figure 15 and Figure 16, it is clearly shown that the two figures have a high degree of similarity, which indicates that the bending of the four-port flexible MIMO antenna does not affect the radiation characteristics of the antenna.
To validate the simulated radiation pattern of the flat and bent MIMO antennas, the radiation patterns of the fabricated MIMO antenna were measured inside an anechoic chamber, as illustrated in Figure 17 (left-hand side). On the other hand, i.e., on the right-hand side, the measurement setup of the bent antenna, supported by a curved foam sheet, appears. In the two cases of flat and bent MIMO antennas, only the port under testing was powered, and the other was attached with 50 Ω.
Figure 18 illustrates the radiation patterns of the antenna. The radiation patterns of port 1 of the flat MIMO antenna at a 3.5 GHz frequency in the φ = 0° and φ = 90° planes are shown in Figure 18a. As shown in the figure, the pattern is omnidirectional in the φ = 0° plane and bi-directional in the φ = 90° plane. The simulation and measurement results of the radiation pattern are well-matched. Figure 18b shows the simulated and tested radiation patterns of the bent flexible antenna at port 1. The bent antenna is omnidirectional in the φ = 0° plane and bi-directional in the φ = 90° plane, which were similar to those obtained for the flat MIMO antenna, which confirms the stability of the proposed antenna in both configurations.

3.4. Peak Gain and Efficiency of the MIMO Antenna

Figure 19 displays the simulated and tested peak gains of the antenna. The fabricated MIMO antenna achieved a peak gain that ranged from 3 to 4 dBi through the desired band for the flat configuration. In contrast, the bent MIMO antenna’s peak gain varied between 3.5 and 4.5 dBi over the same frequency band. It can be observed in Figure 19 that the simulation and measurement curves have the same trends, with little deviation because of the measurement setup. Also, there is little difference between the peak gain of the flat MIMO and that of the bent MIMO, and this was an expected result of the bending of the flexible MIMO antenna.
Moving to Figure 20, we find the simulated efficiencies of the MIMO antenna. The proposed antenna has a radiation efficiency of more than 99%; however, the total efficiency of the antenna ranges from 84% to 96% over the matched frequency band. This result was consistent with the simulated impedance-matching characteristics of the antenna shown in Figure 10. The deepest resonance and, consequently, the maximum reflection efficiency lies at the same frequency as the peak total efficiency, i.e., 3.6 GHz.

4. MIMO Result Validations

The ECC is one of the important parameters used to evaluate the performance of the MIMO antenna. The S-parameters or radiation patterns can be utilized to calculate the ECC according to [39]. The simulated and measured S-parameter-based ECCs for the flat MIMO antenna are shown in Figure 21a. The ECC was tested for port 1 with respect to the other three ports. As shown in the figure, the measured ECC values do not exceed 0.005 within the desired band. The radiation pattern-based ECC of port 1 is shown in Figure 21b. Very low values of the measured ECC can be observed in the figure. The obtained values of the ECC satisfy the requirements of good MIMO operation, i.e., the ECC should be less than 0.5 [40].
Similarly, Figure 22 shows the ECC curves at port 1 while the MIMO antenna was bent with a 50 mm radius of curvature. The S-parameter-based ECC (Figure 22a) and radiation pattern-based ECC (Figure 22b) show very low levels of ECC, which in turn demonstrates the good isolation characteristics between ports.
Figure 23 depicts the DG results of the antenna. The DG can be calculated from the ECC as [41]. Figure 23a depicts the DG of the flat MIMO configuration, while Figure 23b shows the bent configuration. It is clearly shown in the two figures that the measured DG of the two configurations achieved values of more than 9.98 dB within the operating bands. All the recorded values of DG were within the accepted range.
Additionally, the CCL was tested for the proposed MIMO. The accepted value of the CCL should be ≤0.4 b/s/Hz [42]. The CCL simulated and tested outcomes of the flat MIMO antenna are shown in Figure 24a. Similar results are depicted in Figure 24b for the bent MIMO antenna. The proposed MIMO antenna’s CCL lies in the range from 0 to 0.2 bits/sec/Hz over the operating frequency band, both for the flat configuration and the bent configuration, with good matching between the results.
The MEG and TARC are extracted and calculated utilizing the equations in [43,44] and are presented in the simulated outcomes, as illustrated in Figure 25 and Figure 26, respectively. The MEG achieved a value of −3 dB at the four ports within the worked frequency band, as illustrated in Figure 25, for both the flat and bent layouts. Finally, the TARC achieved almost the same level and frequency band at the different phases, as presented in Figure 26. It was concluded that the suggested MIMO antenna operated well, which confirms its diverse features.
A comparison between the proposed four-port flexible MIMO antenna and some similar designs that appeared in the literature is shown in Table 1.

5. Conclusions

A four-port flexible MIMO antenna has been presented. The antenna was matched from 3.2 GHz to 4.12 GHz and has been characterized by its compact size, high isolation, and good radiation characteristics, in addition to its flexibility. The MIMO antenna has 66 × 66 × 0.13 mm3. The performance of the proposed flexible MIMO was tested, and the performance was stable in different cases. The MIMO operation of the proposed antenna was validated through the obtained results: ECC < 0.005, DG > 9.95 dB, and CCL < 0.2 bits/sec/Hz. All the obtained results have been validated experimentally and are in good agreement with the simulation outcomes. The good performance of the antenna demonstrates its suitability for 5G communications.

Author Contributions

Conceptualization, M.A.A. and A.A.I.; methodology, A.A.I. and E.T.; software, A.A.I.; validation, E.T., M.A.A. and A.A.I.; investigation, A.A.I. and H.A.M.; fabrication, and measurements, H.A.M.; writing—original draft preparation, E.T.; writing—review and editing, E.T., A.A.I. and M.A.A. All authors have read and agreed to the published version of the manuscript.

Funding

The authors extend their appreciation to Prince Sattam bin Abdulaziz University for funding this research work through the project number (PSAU/2023/01/25339).

Data Availability Statement

All data generated or analyzed during this study are included in this article.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. The suggested 2D configuration of the flexible single-element antenna: (a) flat, (b) bent around the y-axis, and (c) bent around the x-axis.
Figure 1. The suggested 2D configuration of the flexible single-element antenna: (a) flat, (b) bent around the y-axis, and (c) bent around the x-axis.
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Figure 2. The design steps of the flexible single-element antenna.
Figure 2. The design steps of the flexible single-element antenna.
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Figure 3. The effect of the flexible antenna dimensions on the S11 (a) changing (Y1), (b) changing (X1), (c) changing (Y2), and (d) changing (Lg).
Figure 3. The effect of the flexible antenna dimensions on the S11 (a) changing (Y1), (b) changing (X1), (c) changing (Y2), and (d) changing (Lg).
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Figure 4. S11 measuring setup of the flexible single-element antenna: (a) photo of the fabricated antenna; (b) antenna attached to test feature kit for measuring; and (c) the measured S11 appeared on VNA.
Figure 4. S11 measuring setup of the flexible single-element antenna: (a) photo of the fabricated antenna; (b) antenna attached to test feature kit for measuring; and (c) the measured S11 appeared on VNA.
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Figure 5. S11 outcomes of the flexible single-element antenna in a flat position.
Figure 5. S11 outcomes of the flexible single-element antenna in a flat position.
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Figure 6. The simulated S11 outcomes at different values of the radius of curvature R: (a) bent around the x-axis and (b) bent around the y-axis.
Figure 6. The simulated S11 outcomes at different values of the radius of curvature R: (a) bent around the x-axis and (b) bent around the y-axis.
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Figure 7. The flexible single-element antenna current distribution outcomes at 3.5 GHz.
Figure 7. The flexible single-element antenna current distribution outcomes at 3.5 GHz.
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Figure 8. The suggested layout of the flexible MIMO antenna: (a) flat and (b) bent around the y-axis with R = 50 mm.
Figure 8. The suggested layout of the flexible MIMO antenna: (a) flat and (b) bent around the y-axis with R = 50 mm.
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Figure 9. Photos of the fabricated flexible MIMO antenna: (a) flat and (b) bent around the y-axis at R = 50 mm.
Figure 9. Photos of the fabricated flexible MIMO antenna: (a) flat and (b) bent around the y-axis at R = 50 mm.
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Figure 10. S11 results in a flat position at port #1.
Figure 10. S11 results in a flat position at port #1.
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Figure 11. S21, S31, and S41 results in a flat position at port #1.
Figure 11. S21, S31, and S41 results in a flat position at port #1.
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Figure 12. S11 outcomes at port #1.
Figure 12. S11 outcomes at port #1.
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Figure 13. S21, S31, and S41 outcomes at port #1.
Figure 13. S21, S31, and S41 outcomes at port #1.
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Figure 14. The flexible MIMO antenna results of the current distribution at 3.5 GHz and at port#1: (a) flat position and (b) bent position.
Figure 14. The flexible MIMO antenna results of the current distribution at 3.5 GHz and at port#1: (a) flat position and (b) bent position.
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Figure 15. The 3D patterns of the flexible MIMO antenna in a flat position with individual feeding at 3.5 GHz.
Figure 15. The 3D patterns of the flexible MIMO antenna in a flat position with individual feeding at 3.5 GHz.
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Figure 16. The 3D patterns of the flexible antenna in a bent position with individual feeding at 3.5 GHz.
Figure 16. The 3D patterns of the flexible antenna in a bent position with individual feeding at 3.5 GHz.
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Figure 17. The radiation pattern setup of the proposed flexible MIMO antenna.
Figure 17. The radiation pattern setup of the proposed flexible MIMO antenna.
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Figure 18. The normalized radiation pattern of the proposed flexible MIMO antenna at port 1 with a frequency of 3.5 GHz: (a) flat and (b) bent.
Figure 18. The normalized radiation pattern of the proposed flexible MIMO antenna at port 1 with a frequency of 3.5 GHz: (a) flat and (b) bent.
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Figure 19. The flexible antenna simulated and measured peak gains.
Figure 19. The flexible antenna simulated and measured peak gains.
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Figure 20. The flexible antenna simulated efficiency.
Figure 20. The flexible antenna simulated efficiency.
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Figure 21. The ECC in a flat position at port #1: (a) S-parameters and (b) radiation patterns.
Figure 21. The ECC in a flat position at port #1: (a) S-parameters and (b) radiation patterns.
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Figure 22. The ECC in a bent position at port #1: (a) S-parameters and (b) radiation patterns.
Figure 22. The ECC in a bent position at port #1: (a) S-parameters and (b) radiation patterns.
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Figure 23. The DG results at port #1: (a) flat and (b) bent.
Figure 23. The DG results at port #1: (a) flat and (b) bent.
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Figure 24. The CCL results at port #1: (a) flat and (b) bent.
Figure 24. The CCL results at port #1: (a) flat and (b) bent.
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Figure 25. The MEG results: (a) flat and (b) bent.
Figure 25. The MEG results: (a) flat and (b) bent.
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Figure 26. The TARC results at port #1: (a) flat and (b) bent.
Figure 26. The TARC results at port #1: (a) flat and (b) bent.
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Table 1. The MIMO antenna in comparison with other designs.
Table 1. The MIMO antenna in comparison with other designs.
Ref.Antenna
Size
(mm2)		Substrate εr/Thickness (mm)BW
(GHz)		No. of
Ports		Gain (dBi)/Efficiency (%)Isolation
(dB)		ECCFlexibility
[9]50 × 100FR4 4.4/4.52.7–3.643/8525-No
[12]180 × 180RT Duroid3/1.520.7–1, 2.6–7.245/70˃13˂0.5Yes
[14]120 × 65FR4 4.4/1.63.3–542–4/-18.8˂0.018No
[23]70 × 145polyamide 3.5/0.22.37–5.8545/8517.5˂0.05Yes
[35]150 × 73FR4 4.4//0.83.4–3.64-/51–7420˂0.06No
[36]88 × 88Polyimide3.5/0.052.38–2.5244/80˃15-Yes
[37]71 × 49DAK-3.52.7/0.32.30–2.6011.4/60--Yes
This work66 × 66ROGERS3003/0.133–4.1244/84–96>20˂0.005Yes
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MDPI and ACS Style

Abdelghany, M.A.; Ibrahim, A.A.; Mohamed, H.A.; Tammam, E. Compact Sub-6 GHz Four-Element Flexible Antenna for 5G Applications. Electronics 2024, 13, 537. https://doi.org/10.3390/electronics13030537

AMA Style

Abdelghany MA, Ibrahim AA, Mohamed HA, Tammam E. Compact Sub-6 GHz Four-Element Flexible Antenna for 5G Applications. Electronics. 2024; 13(3):537. https://doi.org/10.3390/electronics13030537

Chicago/Turabian Style

Abdelghany, Mahmoud A., Ahmed A. Ibrahim, Hesham. A. Mohamed, and Emad Tammam. 2024. "Compact Sub-6 GHz Four-Element Flexible Antenna for 5G Applications" Electronics 13, no. 3: 537. https://doi.org/10.3390/electronics13030537

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