Patch Antennas

 Goals

            In this experiment, to understand the basic features of the patch antenna. Designing the patch antenna in various applications using the CST program. It is the examination and application of 2 different feeding types of patch antenna.

Introduction

A patch antenna, also known as a microstrip antenna, is a wide-beam, narrow-band antenna. Its physical geometry is two-dimensional. The simplest patch antenna uses a half-wavelength patch, similar to half-wave dipole antennas, with the metal surface acting as a resonator [1]. A patch antenna is typically made by mounting a molded metal sheet on an insulating dielectric substrate, such as a printed circuit board, and forming a ground plane with a continuous metal layer bonded to the opposite side of the substrate. As a result, it is simple to build and inexpensive to produce. Some patch antennas are made of a metal patch positioned over a ground plane using dielectric spacers rather than a dielectric substrate. The effect is a structure that is less durable but has a greater bandwidth. Patch antennas may be equipped for frequencies ranging from UHF to 100 GHz [3].

Square, rectangular, circle, and elliptical patch antennas are the most common. The form, on the other hand, is not constrained. It is possible to create some continuous form. Patch antennas are physically tough and can be molded to fit a vehicle's curving skin. They're commonly used on the outside of planes and satellites, as well as in handheld radio communications systems. They have a lot of polarization diversity and can handle a lot of different feed points.

Figure 1 shows a microstrip antenna that is fed by a microstrip transmission line. High conductivity metal is used for the patch antenna, microstrip transmission line, and ground plane (typically copper). The patch has a length of L, a width of W, and is mounted on a substrate (some dielectric circuit board) with a thickness of h and a permittivity of ɛ_r. The ground plane's or microstrip's thickness isn't important. The height h is usually much less than the operating wavelength, but it cannot be less than 0.025 of a wavelength or the antenna performance will suffer.

Figure 1.Top View and Side View of Patch Antenna [1]

The length L determines the frequency of operation of the patch antenna in Figure 1. The middle frequency will be roughly determined by:

Inside the dielectric (substrate) medium, the microstrip antenna should have a length equal to one half of a wavelength, according to the equation above. The input impedance is regulated by the width W of the microstrip antenna. Wider widths will also expand bandwidth. The input impedance of a square patch antenna fed in this manner would be on the order of 300 Ohms. The impedance can be minimized by increasing the distance. However, lowering the input impedance to 50 Ohms always necessitates the use of a large patch antenna, which takes up a lot of precious real estate. The width also has an impact on the radiation pattern. The normalized radiation trend is roughly calculated as follows:

k is the free-space wavenumber, which is given by 2π/λ. The magnitude of the fields is calculated as follows:

Figure 2 shows the fields of the microstrip antenna for W=L=0.5 λ.

Figure 2.Microstrip (Patch) Antenna Normalized Radiation Pattern

Patch antennas have a directivity of around 5-7 dB. When looking at the microstrip antenna as seen in Figure 1, the fields are linearly polarized and in the horizontal direction.

1.1.Patch Antenna Design

The patch antenna is made up of;

·         Specifying ɛ_r, f_r and h

·         Determining W and L

·         Designing,

·         For efficient radiator, 

W =     

·         Fing the ɛ_eff

·     Find the

·     Determine L with 

(H.O, 2021)

Figure 3.Top and Side View of Patch [4]

1.2.Advantages

·         Photo etching is used to achieve high precision in processing.

·         It's simple to connect to other computers.

·         Small enough to be used on mobile portable devices.

·         Using microstrip arrays, we can achieve high directivity.

·         A pattern that is difficult to synthesize using a single element can be created using an array of microstrip antennas.

·         When used in conjunction with phase shifters or PIN-diode switches, smart antennas can be developed.

1.3.Disadvantages 

·         Cell phones need a narrow band width (1%) while computers do not (8 percent ).

·         Low performance, particularly for microstrip antennas with short circuits.

·         Aperture and proximity binding are two complicated feeding methods to manufacture.

·         The inclusion of a feed network reduces the productivity of an array. 

1.4.Usage Area of Patch Antennas

Microstrip antennas first appeared in the 1980s. Initially, it was a military project with no regard for expense. As a low-cost technology in the 1990s, this technology was also used for communication applications.

Microstrip(Patch) antennas

·         are favored for low directivity applications;

·         have lower performance;

·         suffer from low efficiency due to feed network for arrays;

·         are ideal for smart antennas; can provide electronic scanning when combined with phase shifters;

·         Photo etching allows for more precise manufacturing;

·         feeding is done by coupling or coax feed lines [3].

 

Shorted patch antennas, also known as planar inverted-F antennas, are a type of patch antenna that is widely used in cell phones (PIFA). A ground pin is used to ground one corner (or one edge) of the patch in this antenna. This version matches better than the regular patch. A written monopole antenna, a variant of patch antenna with a partly etched ground plane, is a very flexible antenna for dual-band operations [2].

Method

Question 1

A typical rectangular patch antenna with coaxial feed is designed in Figure 4. A PEC for ground with a thickness of 0.035mm. A ROGERS 4003 substrate with a thickness of 1.5 mm was placed on top of this plane. The dimensions of the PEC and ROGERS 4003 substrate are the same, the length and width of the plane is 100 mm. A patch antenna with one size of 32.7 and 30 mm is designed on this substrate. A coaxial line is placed under the system to feed this antenna. 

Figure 4.Typical Rectangular Patch Antenna with Coaxial Feed 

Question 2

A ROGER RT 5880 substrate is placed on top of a 30 mm PEC floor. The thickness of this substrate is 0.796 mm. A patch antenna with one dimensions of 16 mm and 12.45 mm is designed. In order to feed this patch antenna, one feed line with a width of 2.46 mm and a length of 7 mm (extending to the substrate material) is defined. One Waveguide port is defined for this feed to energize the antenna from one side of the antenna. Furthermore, width of slot is 2.09 mm. The designed typical patch antenna with microstrip line feed is shown in Figure 5.

Figure 5.The Designed Typical Patch Antenna with Micsostrip Line Feed

Question 3 (Homework)

One patch antenna with microstrip line feed used in aircraft communication systems has been designed. One PEC plane with thickness 0.035 mm, length and width 60 mm and 65 mm is defined for ground, respectively. A ROGERS RT 5880 substrate of the same dimensions and thickness of 1 mm has been defined on this ground plane. On top of this substrate, a patch antenna is designed with a width of 55 mm, length of 27.5 mm, width and length of feed line 3.8 mm, 25 mm, respectively. Also, width and length of slot is 3 mm and 8 mm, respectively. A Waveguide Port has been defined to feed this antenna. There is also the designed patch antenna in Figure 6. 

Figure 6. The Designed Typical Patch Antenna with Micsostrip Line Feed for aircraft communication systems

Results

Result 1

As a result of the simulation of various parameters, the best result that works at 2.45 GHz was obtained when Lp = 31.1 mm. Simulation results are shown in Figure 7. 

Figure 7. Simulation result of various parameters

When Lp = 31.1 mm, the s-parameter circuit of typical rectangular patch antenna with coaxial feed is in Figure 8. Figure 9 contains the details of Figure 8. 

Figure 8. S-parameter of designed rectangular patch antenna with coaxial feed when Lp=31.1 mm

Figure 9. Detailed S-parameter of designed rectangular patch antenna with coaxial feed when Lp=31.1 mm

Resonance Frequency of rectangular patch antenna with coaxial feed is 2.4549 GHz and resonance value of it is -11.4435 dB, according to Figure 10.

Figure 10. Resonance frequency and value rectangular patch antenna with coaxial feed

According to Figure 11, rectangular patch antenna with coaxial feed works between 2.3996 GHz and 2.509 GHz at -3 dB. Bandwidth of this antenna is 0.10936 GHz (2.509 – 2.3996) at -3 dB.

Figure 11. Values of S-Parameter of rectangular patch antenna with coaxial feed at -3 dB

According to Figure 12, rectangular patch antenna with coaxial feed works between 2.4412 GHz and 2.4649 GHz at -10 dB. Bandwidth of this antenna is 0.0237 GHz (2.4649 – 2.4412) at -10 dB.

Figure 12. Values of S-Parameter of rectangular patch antenna with coaxial feed at -10 dB

The total efficiency graphs of the simulation results of various parameters are shown in Figure 13. It can be understood from this graph that it is the most efficient place in Lp = 31.1. When Lp = 31.1, there is a total efficiency graph in Figure 14. The designed antenna has the most result in resonance frequency of when Lp = 31.1 and the efficiency of the antenna is 67% at this frequency.

Figure 13.The total efficiency graphs of the simulation results of various parameters

Figure 14. Total Efficiency of designed antenna when Lp=31.1

Figure 15 shows farfield 3D plotting of rectangular patch antenna with coaxial feed without directivity at 2.5 GHz (resonance frequency).

Figure 15. Farfield of rectangular patch antenna with coaxial feed without directivity at 2. 5 GHz.

Figure 16 shows farfield 3D plotting of rectangular patch antenna with coaxial feed with directivity at 2.5 GHz (resonance frequency).

Figure 16. Farfield of rectangular patch antenna with coaxial feed with directivity 

The H and E plane of rectangular patch antenna with coaxial feed cuts are shown in Figure 17.

Figure 17.The H and E plane of rectangular patch antenna with coaxial feed 

The effect of S11 of the change of Yf of the central point of the coaxial feeding is seen in Figure 18. The best S11 values were at the point Yf = 10.6 mm.

Figure 18. The effect of S11 of the change of Yf of the central point of the coaxial feeding 

When Yf = 10.6 mm, the effect of Xf change of the coaxial feeding center on S11 is seen in Figure 19. The best S11 result occurred at the point Xf = 16 mm.

Figure 19.The effect of S11 of the change of Xf of the central point of the coaxial feeding at Yf=10.6 mm 

           By changing the center points of the coaxial feeding, the best points S11 were at Xf = 16 mm and Yf = 10.6 mm. Also, Figure 20 contains the s-parameter result of this. Its resonance frequency is 2.44 GHz and its resonance value is -33.613 dB.

Figure 20.The Best S11 parameter with changing Xf and Yf 

Result 2

As a result of the simulation of various parameters, the best result obtained when Wf = 2 and c=6. Simulation results are shown in Figure 21. 

Figure 21.Simulation result of various parameters 

When Wf = 2 and c=6, the s-parameter circuit of rectangular patch antenna with microstrip line feed is in Figure 22. Figure 23 contains the details of Figure 22.

Figure 22. S-parameter of rectangular designed patch antenna with microstrip line feed when Wf = 2 and c=6

Figure 23. Detailed S-parameter of designed rectangular patch antenna with microstrip line feed when Wf = 2 and c=6

Resonance Frequency of rectangular patch antenna with microstrip line feed is 6.245 GHz and resonance value of it is -38.348 dB, according to Figure 24.

Figure 24.Resonance frequency and value rectangular patch antenna with microstrip line feed

According to Figure 25, rectangular patch antenna with microstrip line feed works between 6.1169 GHz and 6.3861 GHz at -3 dB. Bandwidth of this antenna is 0.26919 GHz (6.3861– 6.1169) at -3 dB.

Figure 25.Values of S-Parameter of rectangular patch antenna with microstrip line feed at -3 dB

According to Figure 26, rectangular patch antenna with microstrip line feed works between 6.1991 GHz and 6.2948 GHz at -10 dB. Bandwidth of this antenna is 0.095698 GHz (6.2948 – 6.1991) at -10 dB.

Figure 26.Values of S-Parameter of rectangular patch antenna with microstrip line feed at -10 dB

The total efficiency graphs of the simulation results of various parameters are shown in Figure 27. It can be understood from this graph that it is the most efficient place in when Wf = 2 and c=6. When Wf = 2 and c=6, there is a total efficiency graph in Figure 28. The designed antenna has the most result in resonance frequency of when Wf = 2 and c=6 and the efficiency of the antenna is 86.7% at this frequency.

Figure 27.The total efficiency graphs of the simulation results of various parameters

Figure 28.Total Efficiency of designed antenna when Wf = 2 and c=6

Figure 29 shows farfield 3D plotting of rectangular patch antenna with microstrip line feed without directivity at 6.245 GHz (resonance frequency).

Figure 29. Farfield of rectangular patch antenna with microstrip line feed without directivity 

Figure 30 shows farfield 3D plotting of rectangular patch antenna with microstrip line feed with directivity at 6.245 GHz (resonance frequency).

Figure 30.Farfield of rectangular patch antenna with microstrip line feed with directivity

The H and E plane of rectangular patch antenna with microstrip line feed cuts are shown in Figure 31.

Figure 31.The H and E plane of patch antenna with microstrip line feed

Result 3 (Homework)

As a result of the simulation of various parameters, the best result obtained when Ws = 1 and Ls=10. Simulation results are shown in Figure 32. 

Figure 32.Simulation result of various parameters

When Ws= 1 and Ls=10, the s-parameter circuit of rectangular patch antenna with microstrip line feed is in Figure 33. Figure 34 contains the details of Figure 33.

Figure 33. S-parameter of rectangular designed patch antenna with microstrip line feed when Ws = 1 and Ls=6

Figure 34. Detailed S-parameter of rectangular designed patch antenna with microstrip line feed when Ws = 1 and Ls=6

Resonance Frequency of rectangular patch antenna with microstrip line feed is 3.46 GHz and resonance value of it is -30.319 dB, according to Figure 35.

Figure 35.Resonance frequency and value rectangular patch antenna with microstrip line feed

According to Figure 36, rectangular patch antenna with microstrip line feed works between 3.414 GHz and 3.5055 GHz at -3 dB. Bandwidth of this antenna is 0.091524 GHz (3.5055 – 3.414) at -3 dB.

Figure 36.Values of S-Parameter of rectangular patch antenna with microstrip line feed at -3 dB

According to Figure 37, rectangular patch antenna with microstrip line feed works between 3.4415 GHz and 3.4767 GHz at -10 dB. Bandwidth of this antenna is 0.035145 GHz (3.4767 – 3.4415) at -10 dB.

Figure 37.Values of S-Parameter of rectangular patch antenna with microstrip line feed at -10 dB

The total efficiency graphs of the simulation results of various parameters are shown in Figure 38. It can be understood from this graph that it is the most efficient place in when Ws = 1 and Ls=10. When Ws = 1 and Ls=10, there is a total efficiency graph in Figure 39. The designed antenna has the most result in resonance frequency of when Ws = 1 and Ls=10 and the efficiency of the antenna is 74% at this frequency.

Figure 38.The total efficiency graphs of the simulation results of various parameters

Figure 39.Total Efficiency of designed antenna when Ws = 1 and Ls=10

Figure 40 shows farfield 3D plotting of rectangular patch antenna with microstrip line feed without directivity at 3.46 GHz (resonance frequency).

Figure 40.Farfield of rectangular patch antenna with microstrip line feed without directivity

Figure 41 shows farfield 3D plotting of rectangular patch antenna with microstrip line feed with directivity at 3.46 GHz (resonance frequency).

Figure 41.Farfield of rectangular patch antenna with microstrip line feed with directivity

The H and E plane of rectangular patch antenna with microstrip line feed cuts are shown in Figure 42.

Figure 42.The H and E plane of patch antenna with microstrip line feed

Conclusion

The basic features of the patch antenna and the points to be considered while designing were investigated. Changing the size of the patch antenna, its effects on the results were examined. In addition, the effect of the coaxial feeding center of the patch antenna on the S11 was observed. The design of the microstrip fed patch antenna was examined and the resonance frequency and resonance value effect of the width fedd line was observed. The application of patch antenna with microstrip feed used in daily life was made and examined. As a result of these evaluations, the effects of dimensions of slots on the S-parameter were observed. In this experiment, various design and feeding methods of the patch antenna have been applied and compared with the other antenna types made so far. Patch antenna is used in many systems, especially communication.

References

 [1] AntennaTheory, Microstrip (Patch) Antennas, 2021, reached in the  site https://www.antenna-theory.com/antennas/patches/antenna.php.

[2] Wikipedia, Patch antenna, 2021, reached in the site https://en.wikipedia.org/wiki/Patch_antenna#:~:text=A%20patch%20antenna%20is%20a,metal%20called%20a%20ground%20plane.

[3] Radartutorial, Patch Antenna or Microstrip Antenna, 2021, reached in the site https://www.radartutorial.eu/06.antennas/Microstrip%20Antenna.en.html

[4] Dr.H. Odabaşı, Antenna Theory, Eskişehir Osmangazi University Department of Electrical and Electronics Engineering Antenna Theory Lesson Sources, 2021.