MINIATURIZED MICROSTRIP DUAL PATCH ANTENNA FOR 2.4 GHz WIFI APPLICATIONS

The implications of the WiFi technology are rapidly expanded due to the revolution of this technology in the telecommunication domain. The coverage space of the Wi-Fi sources still an issue, which limit the usability of the WiFi in various applications such as home, offices, hotels, and restaurants. The patch antenna is effective technology that can strength the signals gaining and distribution of the WiFi. This study proposes patch antenna design for the indoor WiFi applications of 2.4 GHz. The main objective of this study is to present miniaturized patch antenna of effective Omni-directional radiation based on the 2.4 GHz frequency. The proposed patch antenna is structured as dual rectangle shapes like the eye glass shape. The size of the antenna substrate is 15mm * 25 mm * 1.4 mm in order to ensure the miniaturized properties of the antenna. The bottom side of the substrate is printed with a microstrip feed line, and the copper is the material of the antenna. The proposed patch antenna is applied on S11 parameters that support the WiFi applications of 8.2.11g standard. The operating frequency is 2.4 GHz with 50 Ω as input impedance. The gain mode is about 1.8 dB that constrained by return loss less than -10 dB. To evaluate the proposed antenna, the Vector Network Analyzer is applied using tool called CST Studio Suite. The simulation shows that the proposed antenna address the Omni-directional radiation of 2.4 GHz frequency under gaining loss less than -10 Db. The efficiency of the antenna radiation records about 72%, which is good records comparing with the past studies. The main contribution of this study is the effectiveness of the miniaturized properties of the proposes patch antenna.


I. INTRODUCTION
The development in the telecommunication industry is expanded in the last two decades (Kruger et al., 2015;Gu et al., 2015). The WiFi technology is important telecommunication domain due to its portability features. The portable WiFi devices allow the accessing of the internet services in anytime and from anywhere (Sarkar et al., 2016). There are wide applications of the wireless internet connection using WiFi such as GPS, satellites, in hotels, in home, and in restaurants (Akila et al., 2018). According to Torres-Sospedra et al. (2016), The WiFi is telecommunication technology that can gain and radiate the frequency in the domain range between 2.4-5 GHz. The transfer rate of the WiFi is upt to 54 Mbps, and the radiation coverage space is up t0 200 meters. The WiFi is able to transfer services of any data such as video, audio, and text (Lee et al., 2007). One of the most important challenges that faced by the WiFi is the coverage space and Omni-directional radiation (Hasan et al. 2017; Akila et al., 2018). The limit if the coverage space of the WiFi is 50 to 200 meters, which limit the implications of this technology. On the other hand, the WiFi technology face challenge in radiate the frequencies in Omni-directional like vertical and horizontal directivities (Chen et al., 2017). These two challenges present the importance of the antenna technology to strength the frequency radiation by WiFi devices. The Antenna is an electrical jointer that connected with the source of the signal in order to strength the signal distribution for the destination devices (Akila et al., 2018). Weng et al. (2015) mentioned that the antenna technology was investigated by researchers since the early 1990s in order to improve the coverage space of the radio frequency. There are many factors effects on the antenna effectiveness such as the antennas shapes and sizes (Singh & Tripathi, 2011). For WiFi applications, The patch antenna is most suitable antennas due to its miniaturized properties (Akila et al., 2018). The dimension sizes of the patch antenna are usually designed in millimeters, and the most effective shape is the rectangular (Sharma & Hashmi, 2014;Hasan et al. 2017). The miniaturized properties of the patch anntenas are deal with the portability characteristics of the WiFi devices. On the other hand, the rectangular shape of the patch antenna provides efficient Omni-directional radiation.
Basically, the structure of the patch antenna composed of three main elements namely; substrates, ground, and patch (Sharma et al., 2011). The substrate represents the edges of the antenna, while the ground the bottom side if the antenna. The patch is the core element of the antenna and it is usually made of conducting material such as copper. The patch gain the signals through feed line called microstrip that etched on the dielectric substrate. Then, the patch radiates the signals for the destination devices in the coverage space of WiFi. The sizes of patch antenna dimensions are represented by Width (W) * Length (L) * thickness. Figure 1 illustrates the general structure of the patch antenna. The Microstrip patch antenna is fed with many methods but the most common methods are the coaxial probe, aperture coupling and proximity coupling (Sharma et al., 2011). What happens in the contacting method is that the RF power is fed directly to the radiating patch and in the non contacting method is that the electromagnetic field coupling is done to transfer power between the radiating patch and microstrip line. The most important thing to take note of is the maximum transfer of power that is to say the feed line should match with the input impedance of the antenna. Figure 2 illustrates the microstrip line in the patch antenna. The patch antenna is work based on S11 parameters, which represent the input-output relationship between the communications ports (Sivia & Bhatia, 2015). Simply put, S11 antenna means that there are one direct connection port between the source device and the antenna, and there are one direct connection port between the antenna and the destination devices. Based on the above discussion, the main aim of this study is to design miniaturized patch antenna for WiFi applications of 2.4 GHz frequency. The proposed design would provide efficient Omni-directional radiation under the configuration of S11 parameters. The next section presents related works on the patch antenna for WiFi applications, section 3 explain the research methodology, section 4 discusses the results, and section 5 provide the conclusion and the future works.

II. RELATED WORKS
The shapes of the patch antenna can be designed as circular, square, rectangular, and triangular. However, the rectangular antenna is the most suitable shape due to effectiveness of frequency radiation based on the rectangular vectors (Sidhu et al., 2015;Shumba, 2017). In the antenna of rectangular shape, it is important to address the miniaturized properties of the antenna size. According to Garg (2001), the design of the patch antenna can be performed based on three dimensions; (1) the "dielectric constant of the substrate" (Er), the frequency of operation (fr), and the height of the dielectric substrate (h). Based on these three dimensions, the antenna Width (w) can be decided using the following Equation 1 (Garg, 2001;Sidhu et al., 2015;Shumba, 2017): where c is the light free space velocity On the other hand, the effective length (Leff) of the antenna can be calculated based on the following equation 2 (Garg, 2001; Sidhuet al., 2015; Shumba, 2017): Where Eff is the effective dielectric constant and ∆L is the possible length extension. Eff and ∆L can be calculated using the following formulas (Garg, 2001; Sidhuet al., 2015; Shumba, 2017): Based on equation 3 and 4, the actual length (L) of the patch antenna can be calculated using the following formula 5 (Garg, 2001; Sidhuet al., 2015; Shumba, 2017): The above five equations are helpful to design the dimensions sizes of the patch antenna W * L * T. Another important issue in the antenna design is the microstrip line feed, which is linked to the patch and the microstrip feed have smaller width comparing with the width of the patch and this feed arrangement has the advantage that the feed can be etched on the same substrate to provide a planar structure (Li &Luk, 2016). The inset cut in the patch done to match the impedance of the microstrip feed lines to the patch without the use any additional matching element. All of this is done by properly controlling the inset position. Therefore this is an easy feeding technique is easier in modeling and as impedance matching (Shumba, 2017). Figure 3 shows the insertion techniques of microstrip line feed. The coaxial probe technique of microstrip fed is suitable due to internal insertion, whereby the microstrip protected in the antenna itself (Shumba, 2017).    Figure 4 illustrates the research methodology phases, which consists of three main phases. The first phase is the design of the patch antenna through design the patch shape, material of the antenna, and the sizes of the antenna elements. The second phase is the simulation using CST studio tool, and through this tool the antenna simulation can be developed, and the simulation environment can be identified such as the measurement frequency (2.4 GHz) and S11 parameters. The third phase is the antenna evaluation based on the gaining loss, the radiation efficiency and the Omni-directional pattern.  Based on the above Figure 4, the antenna patch is dual rectangular shape of 6*5*1.4 mm3. The patch is connected with arms of 0.5* 3mm * 0.9mm and basis of 6 mm* 2 mm * 0.9mm. The arms and basis is smaller than the patch in order to increase the gaining effectiveness of the signals that received from the microstrip line. The microstrip fed line is attached with the patch basis, and it is allocated inside the antenna substrate; the tall of the microstrip line is 9 mm * 0.9 mm. The size of antenna ground is 15 mm * 4mm. it is necessary to mention that all sizes of antenna elements are tested based on the S11 parameters of the study environment (2.4 GHz frequency). Using the CST tool, the proposed antenna is tested on the WiFi of 2.4 GHz standard and S11 parameters. Table 2 presents the simulation environment of the proposed antenna. The most important evaluations are the gaining loss based on S11 parameters, the radiation patterns of the proposed antenna, and the radiation efficiency of the proposed antenna. Figure 5 illustrates the gaining loss based on the S11 mode. The gain mode of the proposed antenna is about 1.8 dB that constrained by return loss less than -10 dB (about -21 dB at 2.4 GHz). In other words, the proposed

Stage 1: Patch Antenna Design
Dimensions of antenna substrate, patch, and ground.  Depend on the proposed antenna design, the pattern of the radiation is tested at 2.4 GHz. Take in account that the Omni-directional pattern is one of the important purposes of this study. Figure 6 illustrates the radiation pattern of the proposed antenna design. The test of radiation pattern shows that the proposed antenna design provides effective Omnidirectional radiation at 2.4 GHz frequency. This indicates that the proposed antenna could radiate the gained data for the destination devices in various directions i.e. vertically and horizontally.

V. CONCLUSION AND FUTURE WORKS
This study propose dual rectangular miniaturized patch antenna of size 15 * 25 * 1.4 mm 3 . The design of the antenna is conducted based on the recommended features in the domain of patch antennas for WiFi applications. The simulation results using CST tool show that the proposed antenna is effective in gain the signals (< -10 dB) at 2.4 GHz, radiate the signals in Omni-directional patters, and efficient in radiate most gained signals (72%) at 2.4 GHz. Therefore, the proposed patch antenna could helpful in enhance the coverage space of the WiFi applications at 2.4 GHz. The main contribution of this study is the miniaturized properties of the proposed patch antenna comparing with the previous works in this domain. In the future, the real fabrication would be developed for real testing of the proposed patch antenna.