All three antenna designs use rectangular microstrip patch elements with two insets and slots on both sides of the patch. The patch elements are accompanied by Yagi elements: three director elements and two reflector elements. Through comparison of simulation results, the paper shows that four-element array antenna with combined corporate-series feeding technique performs better compared to antennas with only either series or corporate feeding network.
The proposed corporate-series fed antenna achieves better performance with wide frequency bandwidth of The antenna has an end-fire radiation pattern. Overall performance shows that the proposed corporate-series-fed microstrip patch antenna with Yagi elements is suitable for next generation 5G communication. Progress in the field of technology has become inevitable with the beginning of the industrial revolution.
With the recent implementation of the 4th generation 4G of mobile communication in many countries, the world is now shifting the focus to 5th generation 5G for the future. Owing to the growth in mobile technology across the world and user demands for wireless devices and applications such as Internet of things IoTs that require higher bandwidths has led to a global bandwidth shortage for current wireless cellular networks.
The 5G system shall exploit millimeter-wave bands [ 1 ] and further improve the communication experience. Microstrip patch antennas have been preferred for antenna design because its characteristics are suitable for commercial wireless applications. They are smaller, lightweight, and easy to fabricate; they can have different shapes such as rectangular, square, and triangular, and they support high-density packaging.
Patch antenna manufacturing cost is low. In [ 4 ], a wideband patch array is presented with modified unequal arms.
In [ 5 ], 5G antenna with sector-disk radiating patch placed inside a circular-shaped slot is presented. Modification in the shape of patch antennas has helped to achieve desirable antenna performance.
In addition, patch antennas support various feed techniques and can be developed into arrays to improve the gain and achieve the desired pattern requirements. Owing to these reasons, patch antennas have proven to be a strong candidate for millimeter-wave applications. Thus, 5G antennas have been developed using the microstrip patch technology.
For better results, microstrip array antennas designed using various techniques have also been employed and researched for 5G applications [ 5 — 11 ]. Although millimeter waves are the future of wireless communication, they have few flaws. One of them is the significant free-space path loss caused by their high operating frequency [ 12 ]. Millimeter waves are also susceptible to high propagation loss because of atmospheric absorption. Thus, the factor of high propagation loss because of atmospheric absorption must be considered in the mm-waves antenna design [ 13 ].
The easy feed technique is one of the useful characteristics of microstrip patch antennas in wireless applications. The microstrip patch elements of an array antenna can be fed using a single line or multiple lines depending on the requirement of the system.
There are various complex types of feeding techniques as well. Reference [ 14 ] presented a four-element dual-band printed slot antenna array for 5G which is fed using a modified Wilkinson power divider. In [ 15 ], wideband E-shaped microstrip patch antenna with folded-patch feed in proposed. In both cases, the feeding techniques are of complex nature, whereasa series network is a simple type of feed network that consists of a continuous transmission line through which a proportion of energy is progressively coupled into each element of an array along the line.
Corporate feed is a popular feed technique used for microstrip array antennas. In the case of corporate feed network, the power is equally split at each junction of the microstrip patch array antenna for uniform distribution. Some researchers have combined the series and corporate feed techniques to achieve the desired antenna outputs. However, the antennas mentioned above individually achieved comparatively narrow bandwidths with series feed, corporate feed, or corporate-series feed networks.
Bearing in mind the above considerations, microstrip array antennas with three different feeding techniques are discussed in this study. Rectangular microstrip patch with multiple insets is used as the single patch element for the array antennas. Array antenna with only series feed and only corporate feed networks are designed and simulated, followed by the design of array antenna with combined corporate and series feed network.
Yagi elements are also added to the designs to improve the overall gain and bandwidth. The detailed design of the array antenna shall be discussed in the subsequent sections of the paper.
First, the single patch element to be implemented in arrays with different feeding techniques was designed. For the single patch rectangular element, tentative length and width of the patch were calculated as 1. However, to achieve the desired result of high bandwidth, the parameters of the single patch element were drastically optimized to 5.
The thickness of the microstrip patch was 1. The design was built on a substrate of Taconic RF that has a dielectric constant e r of 4. In the design, a simple inset of size 2. Yagi elements were also added to the design to improve the bandwidth and overall gain.
A pair of reflector elements were placed below the patch, and three director elements were placed above the patch. The distance between director elements and reflector elements was adjusted to achieve the desirable results. The geometry of the finalized single patch element with Yagi elements is shown in Figure 1 , and the dimensions are listed in Table 1. After designing a single patch element that achieved the targeted antenna performance, the patch elements were combined in the next step to form a four-element antenna.
In the first experiment, the four patch elements were combined to form an array using a series feed network. The first patch was fed with a microstrip feedline of width 2. The remaining three patches were subsequently fed through an optimized thin stub of width 0. The parameters of each single patch elements were unchanged, whereas only the size of the overall antenna was changed. All the patch elements were arranged in series, separated by a distance of stub length L st.
Different parameters for the length of the stub were tested to achieve wide bandwidth. Two reflector elements and three director elements of size similar to the ones in single patch element were placed below the patch element close to the microstrip feed and above the last patch element in the series, respectively. Thus, an array antenna with four single patches, Yagi elements, and a continuous ground plane capable of operating around the millimeter-wave spectrum was achieved.
When the patches are arranged in series, the width of the antenna is compromised. In the design, adding more patch elements in series to obtain a bigger array does not increase the width of the antenna. However, the length of the antenna increases drastically, and the antenna performance is affected. The geometry of the array antenna with a series feed network is shown in Figure 2 , and the additional dimensions are listed in Table 2. A simple array antenna fed with the series feed technique with Yagi elements was designed and simulated in HFSS.
The array antenna was simulated with different stub lengths. The stub length in which the bandwidth performance of the antenna was wide was chosen. As seen in Figure 3 , S 11 of the array antenna with stub lengths 2.
The return loss for the array antenna with stub length less than 3. Though the return loss is higher for stub lengths 4. Since, the target of the paper is to achieve wider bandwidth, stub length 3. Figure 4 shows the peak realized gain of the array antenna. The addition of Yagi elements not only increased the bandwidth but also improved the overall gain, with antenna achieving the highest peak realized gain of 7.
Typically, single patch elements are combined to obtain the final array antenna. Thus, in such cases, the return loss characteristics of an array antenna are similar to those of the single patch element.
In the presented case, although most of the parameters of a single patch element are kept unchanged while designing the array antenna, the placement of Yagi elements in the array antenna is different. While the director elements of Yagi elements in a single patch are above the patch, director elements are placed only above patch element on the top of array antenna.
Similarly, the reflector elements are placed only below first patch of the series array. Because of these changes, the return loss characteristics of the array antenna are different from that of a single patch element. Figure 5 shows the radiation patterns of the array antenna at As seen from the plot, the antenna has achieved end-fire radiation pattern at higher frequencies with the employment of Yagi elements to the design.
The radiation patterns closer to lower cut off frequencies were not desirable as seen at The performance of the antenna is more directive at frequencies closer to upper cut-off frequencies. For the second experiment, four patch elements were combined to obtain a corporate-fed array antenna. Similar to the series-fed array antenna, the parameters of the single patches and Yagi elements of the corporate-fed array antennas were kept same.
At first, the feedline was designed for which, by using microstrip formulas, the tentative width of the feedline was estimated around 3. Using [ 22 ], a tentative length of the microstrip was found as 5.
In the beginning, the power divider was designed and tested, using the calculated parameters. Later, the parameters were optimized to achieve desirable results. The width of the first feedline was changed from 3. Different lengths of the first feedline were simulated during the design, and the one that resulted in the desirable output was selected. The length of the second feedline is equal to one-fourth of the length of the first feedline i.
The T-junction opens into two sections. The total size of the feed of the primary T-junction is 2. The parameters of the feedlines of the secondary T-junction power divider are the same as that of the primary. Further, two single patch elements were placed on top of each secondary T-junction power divider, thereby making four single patch elements. Here, the distance between the two patch elements in a secondary T-junction power divider is The triangular slits were also made in the center of the T-junction to improve the return loss characteristics of the antenna.
The parameters of the single patch element are the same for all. The dimensions of the director elements and reflector elements of the Yagi elements are also the same as that of the single patch element. The director elements are placed above every patch element, whereas the reflector elements are placed only at the open end of the single patch. Thus, each single patch is accompanied by only one reflector element below it. The geometry of the corporate-fed array antenna is shown in Figure 6 , and the dimensions are listed in Table 3.
Figure 7 shows the return loss of the antenna with different lengths of the first feedline, that is, L f1. Three different lengths were chosen for the test. At first, antenna was simulated with the feedline length same as the length of the single patch element, that is, 5. Then, the antenna was tested with the length of first feedline L f1 and one-fourth the width of first feedline more or less, that is, 5. The length of the second feedline L f2 was set one-fourth of the length of the first feedline i.
As observed in the figure, the return loss of the array antenna produced multiple bandwidths when the lengths of the first feedline were 5. Thus, the length for the first feedline, L f1 , is set as 4. Figure 8 shows the peak-realized gain, and as seen in the figure, the antenna achieved the highest peak realized gain of 8.
The addition of Yagi elements improved the gain of the overall operating region of the antenna. Figure 9 shows the radiation pattern of array antenna at However, the antenna shows directive characteristics at frequencies closer to lower cut-off region as well.
In conclusion, the antenna achieved end-fire radiation pattern at higher frequencies, with slight improvement in overall radiation pattern compared to series-fed array antenna. After designing and testing series-fed and corporate-fed array antennas with Yagi elements, finally, the corporate and series feeding techniques were combined to form corporate-series-fed microstrip array antenna.
Two patch elements are fed equal power of the ohm source using a network of a microstrip line in the form of the T-junction power divider. Here, the values are obtained by inserting a series of gamma probe GPOBE2 elements in the circuit schematic at the junctions between the feed network and the EM structure subcircuit.
The "Active Impedance" graph will update slightly as each radiator couples to others. The isolation resistor in the Wilkinson feed networks helps mitigate the different impedances seen by each patch as the array is steered.
If you change the "Global Definition" Riso to a large number, such as , there is no longer isolation between each path of the Wilkinson and the impedances of the individual patches will vary much more.
Note that these are essentially calculated by the closed form formula inserted in the schematic "Module". Observe that in the array EM structure, the centers of the adjacent array elements are separated by mils along both x and y. Global variables "XPos" and "YPos" are two linear arrays both with a step size of These are used to determine the magnitude and phase of port excitations so as to steer the main lobe.
Exact origin of the coordinate system is not important. Shifting the origin would move the phases of all port signals uniformly by the same amount.
Due to symmetry, coupling between ports 1 and 2 should be very close to that between ports 13 and There are some difference between the S-parameters as shown in this graph. Consequently, the active impedances shown in graph 5 also lack the expected symmetry. Rerunning the simulation would cause the corresponding pair of curves to overlap with each other. The "Manifold" schematic then builds up the single divider into a 4 way divider.
The "Module" schematic uses values defined in the "Global Definitions" document as well as patch position row and column passed into the schematic from the higher levels of hierarchy to calculate the phase and attenuation needed to feed each patch element. View the global definitions to see which values are defined there and then view the "Module" schematic to see the equations to calculate the phase and attenuation.
The procedure for requesting AWR support has changed.
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