An eye bolt shape slotted microstrip patch antenna design utilizing a substrate-integrated waveguide for 5G systems

Antenna design is usually done on FR4 substrates, since they have a dielectric constant of 4.4, and a loss tangent of 0.02. The proposed microstrip patch antenna operates at 28 GHz and incorporates substrate-integrated waveguides (SIW) in a 0.8 mm thick FR4 substrate into the design to increase bandwidth performance so that the 5G network can function reliably. In comparison with conventional patch antennas, substrate-integrated waveguides bear the advantage of being able to shift to a frequency of 29 GHz, therefore resulting in a more effective antenna. A slot of eyebolt shape has been added to the patch to increase antenna gain. The design was simulated with HFSS software, and it was able to attain a maximum bandwidth of 8 GHz (28%), a gain of 5.5 dB, and a minimal return loss of −38 dB. The VSWR of this antenna is 1.02, which indicates good impedance matching, and a high efficiency of 87% has been achieved as a result. This is a low-profile antenna that combines enhanced bandwidth with the ability to be mounted at the edge of a device, making it an ideal choice for the use of 5G technology to enable machine-to-machine communication.


Introduction
A number of countries around the globe have implemented 5G because of its ability to offer ubiquitous connectivity and low latency [1].A trail being blazed in many countries creates innovation for the twentyfirst century [2].This makes it possible to provide uninterrupted services such as online education that require a high data rate and high bandwidth [3].In addition, it enables many other useful services such as the ability to connect appliances, access home security, carry out robotic farming remotely, monitor your health, track your shipping containers and logistics, and a number of other things.The provision of a large bandwidth is therefore necessary in order for all the services to be compatible with each other concurrently.For this reason, a new antenna needs to be designed in a compact size and to be equipped with special features [4], [5].
With increased bandwidth, this design works with 5G which is going to be introduced in many countries and which will revolutionize the way the world handles data communication [6].For improving the bandwidth of an antenna, there are many performance enhancement techniques that can be applied, such as substrate material, shape of the antenna, slots in the antenna, metamaterial, substrate-integrated waveguide (SIW), etc., all of which can have an impact on the output performance.Shorting pins are one way of increasing gain by arranging an array of circularly polarized antennas [7], [8].It is possible to communicate over milli-meter waves using an antenna array that consists of a multilayer PCB and an airfilled substrate [9], [10].Furthermore, for the purpose of maintaining high isolation, different ports can be used [11].In addition, an antenna which has a cavitybacked slot may also improve performance in applications requiring the capability to operate in the ISM band [12].
A key component of 5G systems is Multi-Input Multi-Output (MIMO) antennas that provide a good envelope correlation coefficient and ensure no loss in channel capacity over the spectrum.The substrateintegrated waveguide plays a significant role in enhancing bandwidth without compromising antenna performance which, in turn, facilitates the fabrication of printed circuit boards [13], [14].Waveguides mounted on the substrate of the rectangular microstrip patch antenna increase bandwidth significantly, allowing for a variety of services to be carried out.Probably, when the future becomes more advanced, tri-band will be able to meet the needs of these services as a starting point for multiband [15].Hence, slow substrateintegrated waveguides with reduced antenna sizes have been developed to provide better performance for this application [16].A defected ground structure was found to provide better return loss than an unflawed one, but at the price of a limited bandwidth [17].Moreover, Air has been found to be a suitable substrate for fabricating antennas because it reduces fabrication costs and increases gain with less bandwidth [18].SIW cavity-backed gap-coupled patch antennas are capable of addressing large bandwidth demands for future Internet of Things applications [19].

Exploration of a microstrip patch antenna design process
Located on the top of the substrate is the antenna, with the full ground plane at the bottom reducing the level of back radiation.Microstrip patch antennas are designed in accordance with • Operating frequency, f o .
• Height of the substrate, h s .
• Relative Permittivity of the substrate, r .
A common substrate used in these applications is FR4 because of its low cost and availability, with a r of 4.4 and a loss tangent (tanδ) of 0.02.The antenna was developed for the 5G system using a substrate with a thickness of 0.8 mm, operating at 28 GHz.
a) The width W p and length L p of the patch are determined by (1) b) In order to determine the width W s , W g and length L s , L g of the substrate and the ground plane, respectively, the following equations can be used: A = z 0 60 d) The proposed system incorporates the inset feed in order to match the impedance between the antenna and the transmission line.A measurement of the inset cut's length Li and width Wi is given by e) The substrate-integrated waveguide design requires the following two conditions where d = diameter of metalized via hole The design process of 28 GHz with different stages is explained in the following diagram.
Figure 1 illustrates the proposed antenna design using HFSS software for use in 5G applications in the 28 GHz band.The design dimensions of this antenna are presented in Table 1.
As shown in Figures 2 and 3, the top view of the antenna is presented as well as the side view of the antenna.

Improved design and simulated results for the optimal patch antenna
This work involves the development and simulation of conventional rectangular microstrip patch antennas   (Ant1), a slotted patch antenna (Ant2), a substrateintegrated waveguide (SIW) patch antenna (Ant3), and a slotted SIW patch antenna (Ant4) using HFSS software.Antennas of the above design are fabricated using FR4 substrates, each of which has r = 4.4, tan δ = 0.02 and thickness (h s ) = 0.8 mm.In the case of antenna without SIW cavity, the resonant frequency is 28 GHz, whereas in the case of an antenna with SIW cavity, it is 29 GHz.The bandwidth of the microstrip patch antenna is increased by incorporating substrateintegrated waveguides.

Microstrip patch antenna without slot & SIW (Ant 1)
A conventional rectangular microstrip patch antenna is shown in Figure 4 with a quarter-wave transformer.
Figure 5 illustrates the return loss of a conventional antenna that is suitable for 5G communication.The simulated return losses are less than −10 dB, which is about −24.9 dB at 28 GHz with 5Ghz bandwidth over the frequency bands 26Ghz to 31Ghz, which covers the required spectrum for 5G.This conventional antenna  with a −24.9 dB return loss will match the impedance requirement.The VSWR value calculated using a resonance frequency of 28.00 GHz is 1.1226 as indicated in Figure 6.A plot of the total gain pattern is shown in Figure 7 for the angles of 0 °to 90 °in the planes.It achieves a peak gain of 5.25 dB at θ = −30 °and 4.16 dB at θ = 0 °. Figure 8 shows a 3-dimensional representation of the radiation pattern for Ant 1 at 28 GHz in form of a 3D model.

Slotted microstrip patch antenna without SIW (Ant 2)
As shown in Figure 9, an eye bolt-shaped slotted microstrip patch antenna without SIW is represented in three dimensions with an inset feed for impedance matching.
In Figure 10, the Ant 2 performance with improved return loss is shown.It is bounded by −28.19 dB with 5.4Ghz bandwidth, which exceeds Ant1.Based on Figure 11, the VSWR value calculated at 28.00 GHz is 1.08.Using the same angle of 0°to 90°in the planes as shown in Figure 12, a plot of the total gain pattern is shown.During operation at θ = −30°, it achieves a peak gain of 5.44 dB and at θ = 0°, it achieves a peak gain of 4.29 dB.An illustration of the radiation pattern for Ant 2 at 28 GHz in the form of a 3D model is shown in Figure 13.

Microstrip patch antenna without slot & with SIW (Ant 3)
Ant 3 is intended to enhance the bandwidth of the network.With HFSS, the dimensions of the radiator, feedline, substrate, and slots in patch are adjusted as shown in Figure 14.The frequency changes to 29 GHz due to the substrate-integrated waveguides.
As illustrated in Figure 15, the Ant 3 has improved its performance as it has an improved return loss.As a result, it is constrained by −37.39 dB and has 8Ghz    bandwidth, which is greater than that of Ant1 & 2. In accordance with Figure 16, the VSWR value calculated at 29.00 GHz is 1.0223.In Figure 17 where the planes are angled from φ = 0°to φ = 90°, a plot of the total gain is illustrated.The maximum gain achieved at θ = −30°is 5.32 dB, and at θ = 0°it is 4.0 dB.The radiation pattern of Ant-3 at 29 GHz is shown in Figure 18 using a 3D visualization.

Slotted microstrip patch antenna with SIW (Ant 4)
Figure 19 illustrates the geometrical configuration of Ant 4 operating at 29 GHz with an eye-bolt shape slot in the substrate-integrated waveguide required for 5G communication.
It is noteworthy that Ant 4 had a return loss of −38 dB, which is higher than previous antennas.In terms of bandwidth, this antenna works at 8Ghz.Accordingly, Figure 20 shows the loss characteristics that can be attributed to Ant 4, which is suited for 5G.This antenna's VSWR value was found to be 1.0213 at 29.00 GHz, providing adequate impedance matching for 5G networks Figure 21.The gain pattern is shown in Figure 22, corresponding to φ = 0 °and φ = 90 °.On the basis of the figure, it can be seen that the peak gain of Ant 4 is 5.5 dB at φ = 0 °and θ = −30 °, and 4.00 dB at φ = 90 °and θ = 0 °.A 3D simulation of the radiation pattern of Ant-4 operating at 29 GHz is shown in Figure 23 to illustrate the pattern.A significant influence on antenna performance is the amount of return loss available to the antenna.Figure 24 illustrates the comparative graph of return loss by the proposed models.Table 3 gives the comparison of various size of the microstrip antennas.Of all the antennas mentioned in the table, the proposed antenna has increased to a maximum bandwidth of 8 GHz (28%) which provides more services in the 5G systems.

Conclusion
In this paper, we propose the use of substrate-integrated waveguide antennas with an eyebolt shape slot to provide immense connectivity due to the necessity of  5G systems, while providing low-latency at the same time.This new patch antenna can provide a much higher bandwidth than many traditional patch antennas due to the incorporation of substrate-integrated waveguides on the substrate, which raises the bandwidth of the proposed patch antenna to 28% at 28 GHz, which is still higher than many other conventional patch antennas.Using an eyebolt shape slot, the antenna is able to attain a gain of up to 5.5 dB, which translates to a higher gain for the user.The simulation is carried out using the HFSS tool and the efficiency of the system is estimated to be 87%, achieving return loss of −38 dB as well as VSWR of 1.02.It is therefore imperative to select the optimal performance technique for maximizing the bandwidth of this antenna, such as substrate-integrated waveguides.

Figure 5 .
Figure 5. Loss characteristics of a conventional antenna configured for 5G based on its frequency.

Figure 6 .
Figure 6.Diagram demonstrating the voltage standing wave ratio as a function of frequency for conventional antennas on a 5G network

Figure 7 .
Figure 7.Total gain pattern of Ant 1 at 28Ghz along the xz and yz directions.

Figure 10 .
Figure 10.Loss characteristics of Ant 2 configured for 5G based on its frequency.

Figure 11 .Figure 12 .Figure 13 .
Figure 11.Diagram demonstrating the voltage standing wave ratio as a function of frequency for Ant 2 on a 5G network

Figure 16 .Figure 17 .Figure 18 .
Figure 16.Diagram demonstrating the voltage standing wave ratio as a function of frequency for Ant 3 on a 5G network

Figure 20 .
Figure 20.Loss characteristics of Ant 4 configured for 5G based on its frequency.

Figure 21 .
Figure 21.Diagram demonstrating the voltage standing wave ratio as a function of frequency for Ant 4 on a 5G network

Figure 22 .
Figure 22.Total gain pattern of Ant 4 at 29Ghz along the xz and yz directions

Figure 24 .
Figure 24.Comparative graph of the models proposed

Table 2 .
Parameters and Evaluation of the results.

Table 3 .
Analogy between the proposed antennas and other antennas.