Design of Rectangular Microstrip Antenna 1x2 Array for 5G Communication

Microstrip antennas are currently popular because they have the advantage and meet the demand for small and lightweight antennas so that they are compatible and easy to integrate. This study aims to design an antenna microstrip rectangular 1x2 array, a rectangular patch microstrip antenna consisting of two elements. The antenna has a patch size of 19.5 mm x 26.5 mm array 1x2 with a frequency of 3.5 GHz. The antenna design is made in a simulation that works at a frequency of 3.5 GHz, and the substrate material is made of FR 4, which has a constant (ε r of) of 4.3, while patch materials are made of copper. Calculating the value of the initial antenna parameters will be optimized by sweeping the parameters to obtain the desired return loss, VSWR, gain, bandwidth, and directivity. The results of optimization of the rectangular microstrip antenna design 1x2 array work at a frequency of 3.5 GHz with a return loss -12.54 dB in the frequency range 3. 47 GHz up to 3.53 GHz, bandwidth 66.5 MHz, VSWR value of 1.6 and produce a gain of 5.5 dB.

The evolution of mobile communication technology has had a huge impact on the lives of the world's people. In the last decade we have witnessed a revolution in how humans communicate, share ideas and live through wireless communication networks. Both use third generation (3G) and fourth generation (4G) mobile networks. The world is currently preparing with the fifth generation (5G) as a platform that can integrate various wireless communication technologies with various types of services in it as well as the ability to provide connections whenever and wherever we are. Based on Vigilante [6] and Dahmal [7] t5G ecology will surpass previous technologies giving birth to a term called networked society, which is a connection that can reach everything around us.
In cellular telecommunication systems, antennas are one of the most important components. The use of high frequencies can cause the dimensions of an antenna to shrink, so 5G technology requires an antenna that is easy to integrate. One type of antenna that is suitable to be a candidate for 5G technology, namely microstrip antennas. Microstrip antennas are thin, small, easy to integrate and can operate at high frequencies. However, microtsrip antennas have a disadvantage, namely narrow bandwidth [8], so special techniques are needed to be able to increase the bandwidth of microstrip antennas. In addition, microstrip antennas produce a small gain, so the technique of array preparation is needed. Array array array arrangement can increase the gain and rectivity of an antenna [8], so that the direction of the antenna beam becomes more directional. This is indispensable in 5G technology [9].
In the previous study in 2019, research that has been conducted by (Fajar Wahyu Ardianto, et al., 2019), has conducted research by designing a microstrip antenna with a rectangular patch shape that is added U-sloton the patch with the aim to increase antenna bandwidth and ableto work at a frequency of 28 GHz, then arranged in an array of 1×2 to increase antenna gain. In addition, the designed antenna has a unidirectional radiation pattern and is linearly polarized. Thus, antennas are used for communication purposes in 5G [ 10] technology. In this study, researchers will design and analyze the performance of the rectangular 1x2 array microstrip antenna at a frequency of 3.5 GHz and expected the results of the Voltage Standing Wave Ratio (VSWR) parameter test ≤ 2 and test the return loss parameters ≤ -10 dB.

Antenna Design
The microstrip antenna forms a rectangular patch 1x2 array working at a frequency of 3.5 GHz. The study used Cooper and FR-4 materials. Cooper material will be used as a patch and ground material with a thickness of 0.035 mm, while FR-4 material has a thickness of 1.6 mm used for substrate material. An antenna will work well if it meets several conditions, including having a Voltage Standing Wave Ratio (VSWR) value of ≤ 2, a return loss value of ≤ -10 dB, and a gain of ≥ 3 dBi.
The antenna design is designed to be able to work on Band-L frequencies. This study is expected to have the following parameters: • Frequency As for calculating the length and width of the ground plane and substrate can be calculated using equations 5 and 6.
is the length of the ground plane and substrate, is the width of the ground plane and substrate, and X is the multiplier factor with a value of ≥6.

b. Feed Channel Width on Rectangular Patch Microstrip Antenna
The width of the antenna utilization channel also greatly affects the performance of the antenna. Therefore the width of the antenna utilization channel can be calculated using equations 7 and 8.
ℎ is the thickness of the substrate material, is the constant that has a value of 3.14, is the dielectric constant of the substrate and is the impedance value of the feed line. From the equations described above, it can be known the importance of parameters to make the design of rectangular microstrip antennas as follows: Once the entire parameter value is known, the researcher can create a single patch microstrip antenna design as in figure 1. a and Figure 1.b is a combination of a patch, substrate, and ground plane design. The length and width of the ground plane element is the same as the substrate, but has a different thickness. The ground plane element is 0.035 mm thick using Copper, while the substrate thickness is 1.6 mm using FR-4.  Once the entire parameter value is known, the researcher can create a rectangular 1x2 array microstrip antenna design as in figure 1.b above. Patch elements use Copper material with a material thickness of 0.035 mm. The design of the microstrip rectangular 1x2 array antenna patch element consists of 2 rectangular antenna elements. The feedline is used as a connection between patches that can be searched by the Wilkinson power divider technique. Design a 1x2 array microstrip rectangular antenna patch with a patch length of 19.5 mm and a patch width of 26.5 mm at a frequency of 3.5 GHz.

Antenna Result
Antenna measurement starts from a working simulation at a frequency of 3.5 GHz with a 1x2 array microstrip antenna design for 5G communication with several specifications, namely rectangular patch shape, 3.5 GHz frequency, produces a return loss value of less than -10 dB with a gain of more than 3 dBi, has a VSWR value of 0 to less than equal to 2 and vertical polarization.

Return Loss
Return loss compares the amplitude of the reflected wave to the amplitude of the transmitted wave. Return loss can occur due to impedance discrepancy(mismatched)between the transmission line and load input impedance (antenna). The return loss value must be less than -10 dB for the antenna to be used. So the smaller the return loss value, the better the antenna to be designed.   Figure 2 above is a graph of the combination of return loss values for single patch antennas and 1x2 array antennas. It can be seen from the graph above that the return loss value for the single patch antenna is symbolized by the type of dashed line and diamond shape marker, the return loss value found at the 3.5 GHz intermediate frequency is -37.812 dB, the return loss value found at the lower frequency 3.4628 GHz is -9.9989 dB, and the top frequency of 3.536 GHz is -9.9939 dB, resulting in a bandwidth of 73.2 MHz. The return loss value on the 1x2 array antenna is symbolized by the type of solid line and circular shape marker, the return loss value contained in the 3.5 GHz intermediate frequency is -12,543 dB, the lower frequency of 3.4681 GHz is -9.9973 dB, and the upper frequency is 3.5346 GHz. of -9.9839 dB resulting in a bandwidth of 66.5 MHz.

Voltage Standing Wave Ratio (VSWR)
VSWR is the ratio between the maximum standing wave amplitude (standing wave) (| V|max) with minimum (|V|min). There are two components of voltage waves in the transmission line, namely the voltage transmitted (V0 +) and the reflected voltage (V0-). The comparison between the reflected voltage and the one transmitted is referred to as the voltage reflection coefficient(Γ) [12].

Gain
A gain is related to the antenna's ability to direct its signal radiation and also the reception of the signal from a certain direction. The gain of an antenna is the ratio of the maximum radiation intensity of an antenna to the radiation intensity of a reference antenna with the same input power. The amount of antenna gain is expressed in dB units against the reference antenna. Figure 5 below shows the frequency graph against the gain value with the unit dB, in the graph there is a value of frequency and gain [11].  In the design of rectangular antenna 1x2 array for 5G communication with a frequency of 3.5 GHz. In figure 5 above, it can be known that the value of gain at the intermediate frequency of 3.5 GHz is 5.5051 dB, at upper frequencies 3.536 produces a gain of 4.8849 dB, and at frequencies below 3.462, the gain value is 5.6188 dB. The microstrip antenna single patch produces gain at intermediate frequency 3.5 GHz of 5. 4668 dB, while at the top frequency 3.536 GHz is 5.4598 dB, and at frequencies below 3.462 GHz has a gain value of 5.4937 dB.

Radiation Pattern
A radiation pattern is a graphically characteristic image of the radiation of an antenna. Antenna radiation patterns are calledfield patternsif theones depicted are strong fields. To state radiation patterns graphically, radiation patterns can be described in absolute or relative form. Relative form means a normalized radiation pattern, where each value of the radiation pattern is divided by its maximum value. In figure 6 below shows a graph of radiation patterns resulting from simulated directivity of single antenna microstrip antennas and 1x2 arrays. In figure 6.a above, it can be known that the value of the result of the antenna radiation pattern at a frequency of 3.5 GHz produces the main lobe magnitude of 6.19 dBi, main lobe direction of 3.0 degree, angular width (3dB) of 99.4 degrees, and sidelobe level of -14.2 dB. In figure 6.b, main lobe magnitude value of 9.32 dBi, main lobe direction of 5.0 degree, angular width (3dB) of 82.6 degrees, and sidelobe level of -16.5 dB.

Conclusions
The result of the design of a rectangular 1x2 array and single patch microstrip antenna with a frequency of 3.5 GHz, then the conclusion that can be taken is for the 1x2 array microstrip antenna to produce a return loss value of -12.6 dB, VSWR 1.6, gain 5.5 dB, bandwidth 66.5 MHz. On microstrip antenna single patch produces a return loss value of -37.8 dB, VSWR 1, gain 5.5 dB, bandwidth 73.2 MHz.