Quad Octagon with Ground Defection Dual Band MSPA For WiMAX and WLAN Technologies

s huge number of applications have been found for a Micro-strip antenna due to its compact and small structure, a quad octagon-shaped dual-band and broadband Micro-strip antenna has been discovered for consumer applications such as (2.1GHz and 5.4GHz). This research work is obtained by combining four octagon-shaped patch structures with a micro-strip feed line and a partial ground structure. The presented microstrip antenna is suitable for providing dual-band output i.e., a frequency band from 1.672GHz to 2.788GHz and a frequency band from 4.876GHz to 6.232GHz. The resonance frequency of the projected antenna is at 2.58GHz and 5.39GHz. Results display that the antenna attains a good return loss(—S − 11 —) outcome characteristics. The intended antenna can manage 1.116GHz impedance bandwidth (BW) and 50.04% & 24.41% fractional BW below -10dB making it more applicable for WiMAX and WLAN technologies. The antenna has been tested on an FR-4 substrate having a thickness of 1.6mm. The projected antenna has been also examined on CST Microwave Studio. To make the projected antenna for dual-band as well as for broadband the physical proﬁle of four Octagon-shaped patches has been attached to the partial ground. It is important to note that transmitting with higher eﬃciency and lower return loss can be placed in a distant location from residential areas, which will decrease the chances of people getting aﬀected by radiation.


Introduction
Microstrip antennas are widely used in many applications such as aircraft and military because of their many advantages such as low cost, small volume, ease of implementation with circuitry, simple fabrication, and the ability to produce circular and linear polarization. The transmitting with higher efficiency and lower return loss can be placed in distant locations from residential areas, which will decrease the chances of people getting affected by radiation. The fringing fields between the patch edge and the ground plane are primarily responsible for the radiation of microstrip patch antennas. A thick dielectric substrate with a low dielectric constant is required for good antenna performance because it provides larger bandwidth (BW) [1][2][3], better radiation, and higher efficiency. A common configuration results in larger antenna size. To decrease the dimensions of the MSPA, substrates with large insulator constants must be used, which is inefficient and results in a narrow BW. As a result, a trade-off must be made between antenna outcomes and antenna profile [4].
The serious limitation of a narrow slot antenna is its small BW [5][6][7][8]. The BW of an antenna is enhanced by incorporating slots on the patch plane and ground plane. Those slots may change the position of transverse magnetic modes (TM10 and TM01) along with the higher modes (TM12 and TM20) [9]. For achieving broadband characteristics, micro-strip antenna with a star slot on a patch plane and a defected ground structure with Octagon Quad shaped tuning element is proposed for wireless applications (WLAN and WiMAX). They cover the BW from 1.672GHz to 2.788GHz and 4.876GHz to 6.232GHz for -S11-¡ -10dB. In the First Stage, a four-octagon shaped microstrip antenna emerged along with star-shaped slot on a patch plane with a full ground structure has been analyzed. In the second stage, the ground structure is reshaped into defected ground structure (DGS) for analyzing the antenna. In the final stage, microstrip lines are added to the remaining three octagon-shaped patches, which can finally provide BW of 50.04% and 24.41% from band 1 and band 2 respectively.

Advantages of Microstrip Patch Antennas
Microstrip patch antennas are mostly used in wireless applications due to their low-profile structure [10][11][12]. Therefore, they are extremely compatible for embedded antennas in handheld wireless devices such as cellular phones, pagers etc. Some of the principal advantages are listed below: • Low fabrication cost allows for large-scale production due to its light weight and small volume.
• Allows for both linear and circular polarisation [13].
• A low-profile planar configuration that is easily conformal to the host surface.
• It is simple to integrate with microwave integrated circuits (MICs).
• Dual and triple frequency operation capability.
• Mechanical robustness when mounted on rough surfaces.

Antenna Geometry
The proposed designed antenna's geometry and all dimensions are depicted below. The antenna structure presented here was designed and placed in the x-y plane, and it is symmetric about the longitudinal axis. Four Octagon-shapes have been combined to form a patch along with the 50-ohm microstrip line. Impedance matching on top of FR4 substrate (1.6mm thick) is the purpose of this component. The bottom plane of the substrate has a printed partial ground rectangular structure.
A microstrip feed line has been used to power the antenna's SMA connector. Figure 1 shows the optimized dimensions of the antennas that were developed. The whole volume of an antenna is (60×60×1.6) mm 3 .
All Optimized dimensions of the designed patch structure and partial ground structure have been displayed in Figure 1 along with the dimension labels. The antenna dimension and values are displayed in Table 1. All the values are in mm. The table consists of design parameters, like width, height, length, and gaps between different elements of patch and ground.

Antenna Evolution
In this section, we compare Antenna 1, Antenna 2, and Antenna 3. The | S 11 | in antenna 1 patch with full ground structure is not in the chosen frequency band because the impedance matching between patch and ground is not adequate (refer to figure 3 | S 11 | (dB) vs frequency (GHz)). The geometry of antenna evolution from antenna1 to antenna4 is depicted in Figure 2. The ground structure in Antenna 2 has been made smaller in order to ensure impedance matching between Patch and ground, but the return loss(| S 11 |) curve still does not show the optimized value of impedance matching condition between Patch and ground.  The ground structure in Antenna 3 has been cut down below the patch but not below the microstrip feed line. The simulation results of this antenna's return loss(| S 11 |) curve show that the Impedance matching between Patch and ground has been achieved with a return loss(| S 11 |) of -10dB. However, this characteristic does not reach the desired level. Every stage of antenna evolution has been simulated and the respective return loss characteristics are displayed in Figure 3. From the figure, it can be analyzed that the antenna4 has the characteristics which are suitable to find our desired application frequency band.

Result Analysis
The prototype of the designed fabricated antenna is displayed in Figure 4 and a comparison of calculated and experimental characteristics is displayed in Figure 5. The detailed frequency analysis is displayed in Table 2.

Return Loss (| S 11 |) Characteristics
S-parameter characteristics display that the optimized Antenna 4 is providing lower loss at lower cut-off frequencies 1.672GHz and 4.876GHz and the higher cut-off frequencies are 2.788GHz and 6.232GHz. So, this antenna became a dual Broadband Antenna. It can be observed that the projected antenna is resonating at 2.58GHz and 5.39GHz as shown in Figure 5.  Figure 6 depicts the 2D radiation pattern of the projected antenna. The far-field radiation pattern has E-plane and H-plane views, and from the H-plane it can be seen that the pattern is omni directional. The omnidirectional pattern is good for antenna performance.     The 2D Radiation Pattern of the projected antenna has been displayed in Figure 8. At 2.58GHz Omni-directional radiation pattern has been analyzed. The Omni-directional pattern is in H-Plane which is good for the radiation. Radiation parallel to y-axis is has lower directivity than in the perpendicular direction. The 3D Radiation Pattern of the projected antenna has been displayed in Figure 9. At 2.58GHz Omni-directional radiation pattern has been analyzed. Similar to the 3D pattern at 1.996GHz, here also the H-Plane pattern is near omni directional or can say quasi-omni directional but a little bit inclined towards the positive y-axis.

Radiation Patterns (2D and 3D)
For 5.39GHz 2D Radiation Pattern of projected antenna has been displayed in Figure 10. The H-Plane pattern is not omnidirectional but quasi-omni which is less significant in terms of the antenna performance, and respective 3-dimensional radiation pattern has been depicted in Figure 11.  The 3D Radiation Pattern of the projected antenna has been displayed in Figure 11 at 5.39GHz. It is clear from the picture that the radiation is front and in back both directions. The directivity is lower around the sides of the antenna in xy-plane.

Gain, Directivity, VSWR and Efficiencies
The suggested QOPDG antenna was tested for gain in both simulation and experiment, and the results revealed peak gains of 4.31dBi and 4.15dBi, respectively, which are in excellent accord with the antenna's performance. Figure 12 depicts the calculated and experimental gain of the antenna across the frequency range of 1GHz to 7GHz. The directivity of the antenna is 5.104dBi for simulation and measurement, and 4.968dBi for both simulation and measurement displayed in Figure 13. The suggested antenna has a BW of 50.05% (between 1.672GHz and 2.788GHz) and a BW of 24.42 percent (between 4.876GHz and 6.232GHz) when the VSWR is less than two (refer to Figure 14).   Figure 15 shows the antenna's radiation and total efficiency. The highest radiation efficiency is 95%, and the total efficiency is greater than 90%, which is sufficient for the antenna.

Conclusion
Octagon Quad Shaped Dual Band Broadband Antenna has been designed, fabricated, and analyzed in this research work. The results show that the presented or developed antenna has dual-band characteristics, a low return loss(| S 11 |) , and an omni-directional radiation pattern. The projected antenna's reflection