CHAPTER 5 ANALYSIS OF MICROSTRIP PATCH ANTENNA USING STACKED CONFIGURATION

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1 1 CHAPTER 5 ANALYSIS OF MICROSTRIP PATCH ANTENNA USING STACKED CONFIGURATION 5.1 INTRODUCTION Rectangular microstrip patch with U shaped slotted patch is stacked, Hexagonal shaped patch with meander patch is stacked, Fractals on hexagonal patch with meander patch are stacked. These are discussed in this chapter. The first configuration is the rectangular Microstrip patch with U shaped slotted patch stacked achieves from 1.7 GHz to 4.45 GHz range of frequencies. The second configuration is hexagonal shaped patch with side 47.6 mm is stacked with meander patch and achieves multi resonant frequency characteristics. The third configuration is hexagonal shaped patch with side 30 mm is stacked with meander patch and achieves multiple resonant frequencies. The fourth configuration is fractals on 30 mm hexagonal patch is stacked with meander patch and achieved multi resonant frequencies. The details about the above configurations are designed, simulated and analyzed in this chapter. Obviously, the inclusion of multiple technologies in wireless devices will significantly increase their functionality. 5.2 ANTENNA DESIGN WITH STACKING The stacked patch antenna structure is analyzed here. It consists of a driven lower patch, and parasitically coupled hexagonal radiating upper patch shown in figure 5.1. Commonly available substrate, FR4 material can be used for this antenna. Coaxial probe feeding will give simple structure. Figure 5.1: Stacked structure of the patch antenna vertical view

2 Design of U slotted patch stacked antenna U shaped slot is made on a rectangular patch and it is stacked with another rectangular patch. It gives stacking configuration. Figure 5.2:U shaped slotted patch stacked antenna 3D geometry In this figure 5.2, the three dimensional view of the patch is shown. The current distributions are displayed in figure 5.4.The patch of dielectric constant 4.4 dimensions are tabulated in table 5.1. Figure 5.3: Current distributions in the U shaped slotted patch

3 3 Table 5.1 U shaped slotted patch stacked antenna configurations Patch Characteristics Dimension (mm) Length of upper patch 40 Length of lower patch 26.5 Width of the upper patch 30 Width of lower patch 18 Thickness of substrate 6.4 The substrate material used between the patches is FR4 material with dielectric constant 4.4. The upper patch length is 40 mm and the lower patch is 26.5 mm. Figure 5.4: U shaped slotted antenna top view. The width is of 30 mm and 18 mm respectively for both the patches. The substrate thickness between the lower patch and the ground is 6.4 mm. The upper patch is kept 6.4 mm above the lower patch. Hence the antenna thickness is only 12.8 mm. The antenna ground plane has dimensions of 70 mm X 70 mm. It is fed by probe. It is connected to lower patch. This antenna is given in figure 5.4. The proposed antenna is stacked with two layers with slot in between them. The lower layer and upper layer substrate thickness is 6.4 mm having dielectric constant ε r = 4.4 U-shaped slot is made on the centre of the feeding patch with the dimensions of 9.05 mm X1.5 mm and 17 mm X5.95 mm to get the desirable resonant Working principle of U slotted patch The stacked microstrip antenna attains radiation characteristics with utilizing the coupling between the first radiating element and the second

4 VSWR S11(dB) 4 radiating element, when a power is fed to the antenna.figure 5.5 shows the simulation result of reflection coefficient vs frequency as S-Parameter characteristics showing the Return loss and figure 5.6 shows VSWR characteristics as VSWR versus Frequency curve Figure 5.5:S-Parameter of U shaped slotted patch stacked From the above results, a broadband performance is exhibited between 1.70 GHz and 4.45 GHz. A 10 db return loss, wide bandwidth of 2.75 GHz, is obtained in this figure Figure 5.6: VSWR display of U shaped slotted patch stacked Gain vs frequency display is shown in the figure 5.7 to indicate the gain values. It is around 5 db over the frequency range between 2.5 GHz and 4.5 GHz.

5 Gain(dB) 5 The present research work has investigated the effect of introducing variation in dimensions of parasitic patches on the performance of an electromagnetically coupled stacked microstrip antenna Figure 5.7: Gain curve of U shaped slotted patch stacked Figure 5.8: Radar plot results of U shaped slotted stacked microstrip antenna showing radiation pattern Radar plot is shown in figure 5.8 and broadband is achieved with appropriate patch dimensions. Therefore the proposed antenna may be useful in wireless communication applications.

6 6 5.3 MICROSTRIP FRACTAL ANTENNA WITH STACKED PATCH In this research, the multi band microstrip fractal stacked patch antenna characteristics are investigated Working principle of fractal stacked patch Hexagonal shaped patch antenna is stacked with circular shaped meandered patch in first stage. The simulation results are recorded. As a second stage, fractal is made on the hexagonal shaped patch and it is stacked to meandered antenna. This fractal is implemented to give wide bandwidth property. The simulated results of the proposed fractal antenna are provided. Vector network analyzer is utilized for measurement. The measured results were given. Both the simulation and measured results show good correlation in performance. The novelty of the work is using meandered patch as a bottom layer in stacked method. This antenna would be used in wireless communication equipments. For designing circular patch, FR4 substrate is used with a constant of 4.4, and thicknesses 3.2 mm. For the hexagonal patch with thickness 1.6 mm same substrate is used. The design is simulated using the electromagnetic simulator after all the dimensional values are calculated in order to get the required return loss, VSWR and radiation characteristics [25]. Female type SMA connector is attached at the ground plane of the patch. For the hexagonal patch, the design specifications are given below. The number of sides in the hexagon is six; the hexagonal shape is arrived by closing all the six sides. The sum of interior angles is 720 and each angle is 120. The sum of interior angles is calculated as follows. (n-2) x 180 = (6-2) x 180 = 4 x 180 = angle = (n- 2) (5.1) n 720 hence, =120 6 The area of a regular hexagon of side length, t is given by

7 7 3 3 area, A = t 2 (5.2) 2 2 A = 2.59t To explore designs for hexagonal arrays, six elements are considered for generating sub-array of d=λ/2. According to hexagonal properties interior angle is 120 and the exterior angle is 60. d 120 λ cos = 2 r = 0.25 (5.3) 2 r 2 The each side of the hexagonal patch is 30 mm to the centre frequency of 3 GHz, in between GHz Hexagonal patch mm stacked antenna Hexagonal patch dimension of 47.6 mm stacked with meander patch antenna (A13) is designed here. This stacked configuration is introduced in figure 5.9(a). Hexagonal patch stacked is designed with side 47.6 mm and thickness h=1.6 mm, ε r =4.4. It is stacked with multi slit meander patch to give more bandwidth. The side view of the antenna is displayed in figure 5.9(b). This antenna is fabricated as prototype and displayed in figure 5.9(c). (a) (b)

8 Gain(dB) 8 (c) Figure 5.9: Hexagonal patch 47.6 mm stacked with meander antenna (a) Geometry (b) side view (c) Prototype The simulation and measurement results were reported. It gives close relation to each other. The gain vs frequency display is shown in figure It depicts gain is more than 5 db for multi frequencies Figure 5.10: Gain of HF47.6 mm sided stacked meander

9 S11(dB) VSWR 9 Simulation Measurement Figure 5.11: VSWR of HF47.6 mm sided stacked meander Simulation Measurement Figure 5.12: S-Parameter results of HF47.6 mm sided stacked meander Reflection coefficient vs frequency in figure 5.12, 10 db return loss bandwidth of 5.5 GHz, multi band is obtained for the frequencies from 0.5 GHz to 6 GHz. The radar plots are shown in figure 5.13.

10 10 Simulation Measurement Figure 5.13: Radar plot results of HF47.6 mm sided stacked meander showing the radiation pattern Hexagonal patch 30 mm stacked antenna The design of hexagonal patch of 30 mm side, stacked with meander patch is reported here. When stacking of the patch is done, multi band [17] characteristics are achieved due to the increase of the dielectric thickness and the self similarity nature of the fractal structure. Circular patch with radius 47.6 mm is taken and slots are made on the circular patch as meandered. This circular meander patch is used as feeding patch for the proposed design. Hexagonal patch with side 30 mm is taken and fractal iterations are made on that patch to make radiation patch. These two circular and hexagonal patches are stacked [18]-[21] together by the dielectric constant ε r1 = ε r2 = 4.4. The distance between the patches are h1=3.2 mm and h2=1.6 mm. SMA connector is attached to the feeding patch through the ground [8]- [9]. The stacked arrangement is shown in the figure 5.14.

11 Gain(dB) 11 Figure 5.14: The geometry of hexagonal radiating patch 30 mm on circular meander feeding patch Figure 5.15: Gain of hexagonal fractal 30 mm stacked with meander Circular patch with five slots are etched on the patch with the dielectric thickness of h 1 =3.2 mm on the ground dimension of 105 sq. mm. The antenna gain vs frequency is displayed in figure 5.15 and VSWR in figure 5.16

12 S11(dB) VSWR 12 Simulation Measurement Figure 5.16: VSWR of hexagonal fractal 30 mm stacked with meander patch Measurement Simulation Figure 5.17: S-Parameter of hexagonal fractal 30 mm stacked with meander patch Reflection coefficient vs frequency is shown in figure 5.17, hexagonal 30 mm fractal with meandered patch gives multiband of 10 db return loss bandwidth Hexagonal fractal patch antenna Hexagonal fractal patch antenna design is given here. The fractal design is made on the plain hexagonal patch and it is shown in the figure

13 S11(dB) This work of hexagonal fractal is demonstrated by A.Azari et al by using microwave office software [18]. In this research, with modification in the material and ground size, the structure is designed, simulated and prototype fabricated. Measurement Simulation Figure 5.18: S-Parameter of hexagonal fractal patch The radiation results are achieved for the range from 0.5 to 6 GHz.This fractal patch itself gives the results of resonant frequencies at GHz, 2.54 GHz, 3 GHz, 4.45 GHz and from 5.35 to 5.65 GHz only. The reflection coefficient vs frequency as S-Parameter is displayed in figure In this figure of hexagonal fractal, multiband of five resonant frequencies is obtained as 10 db return loss bandwidth Hexagonal fractal patch antenna stacked with meander patch The design of hexagonal fractal patch antenna stacked with meander patch is discussed here. This hexagonal shaped fractal patch is radiating patch, stacked with circular meander patch to form as proposed patch. It is shown in figure The proposed design is simulated by the electromagnetic simulator. The simulated results are furnished in the following section. The design is then fabricated using FR4 substrate and SMA connector is attached to it [26]- [28]. Using vector network analyzer, the fabricated antenna is measured. The following section shows the measurement results. Figure 5.20 shows the fabricated antenna upper layer (top) and ground layer (bottom).

14 14 Figure 5.19: Hexagonal fractal patch antenna stacked with meander Figure 5.20: Radiating upper layer and lower Ground layer of fabricated antenna Meandered circular patch and hexagonal fractal patch are stacked over the ground patch which is displayed in the figure The simulation results of plain hexagonal circular meander patch and proposed fractals on hexagonal stacked antenna are furnished in this section. Also, proposed antenna measurement results are displayed. Figure 5.21 illustrates the reflection coefficient vs frequency as S-Parameter display of plain hexagonal on the stack arrangement. From the graph, multi band [14] performance is known. Resonant frequencies 1.5 GHz, 4-5 GHz,

15 S11(dB) S11(dB) 15 GHz are seen in the graphs. The frequencies below 1.5 GHz and after up to 4 GHz are to be achieved Frequency (GHz) Figure 5.21: S-Parameter of plain hexagonal radiating patch on circular meander patch antenna In proposed fractal antenna, the graph shown in figure 5.22 illustrates the following multi band resonant frequencies at GHz, 0.88 GHz, 1.60GHz, 1.65 GHz, 1.71 GHz, 2.01 GHz, 2.64 GHz, 2.97 GHz, 3.30 GHz, 3.41 GHz, 4.18 GHz, 4.40 GHz, 5.12 GHz, 5.34 GHz, 5.50 GHz, and 6.0 GHz Frequency (GHz) Figure 5.22: S-Parameter result of hexagonal fractal stacked antenna In Figure 5.22, S-Parameter result of hexagonal fractal stacked antenna by simulation is shown. The simulated result parameters are tabulated in Table 5.2 as radiation pattern properties. In that table, radiation

16 Gain(dB) 16 efficiency, gain and directivity values corresponding to the resonant frequencies are furnished. Gain vs frequency display Simulation Figure 5.23: Gain of hexagonal fractal stacked antenna Frequency (GHz) Table 5.2 Radiation pattern properties Radiation Efficiency (%) Gain (db) Directivity (db) For the proposed fractal antenna stacked structure, VSWR, return loss, and impedances in ohms (Ω) are given in the Table 5.3. Figure 5.23 shows the gain vs frequency display of the proposed antenna simulation result.

17 VSWR 17 In simulated frequencies of 5-6 GHz, VSWR values more than 2 are obtained [15]-[17]. VSWR, return loss, impedance parameters at resonant frequencies are shown in the table 5.3. Table 5.3 Various parameters at resonant frequencies Resonant Frequency (GHz) VSWR Return Loss (db) Impedance (Ω) j j j j j j j j j j8.7 VSWR vs frequency result is shown in figure 5.24 and figure 5.25 shows the impedance vs frequency parameter graph, known as Z-parameter. In that graph, frequencies 5.6 and 6 GHz are at high impedances are tabulated in Table 5.3. It shows the less radiation effect in those frequencies [18]-[20]. Simulation Measurement Figure 5.24: VSWR display of the proposed antenna The measured result data of the proposed antenna after fabrication is displayed in table 5.4. The measurement result shows the various frequencies resonating less than -10 db to achieve the radiation making a

18 Z (Ohms) 18 useful multi band antenna in the areas of L-band of microwave ( GHz), S-band (2-2.9 GHz), Wimax band ( GHz), and downlink frequencies ( GHz). In the Table 5.4, both simulation result and measurement results were tabulated as a comparison purpose [21]-[22]. Re[Z(1,1)] Im[Z(1,1)] Figure 5.25: Z - Parameter of the proposed antenna Table 5.4 Comparisons of simulation and measurement results Sl. No. Frequency (GHz) Simulated Return Loss (db) Measured Return Loss (db)

19 S11(dB) 19 Measurement Simulation Figure 5.26: Return Loss Parameter of the proposed antenna The maximum radiation is occurring at some frequencies. Comparison of simulation and tested results of reflection coefficient vs frequency are given in figure (a)

20 20 (b) Figure 5.27: Radiation Pattern at GHz (a)elevation angle (b) Azimuthal angle This comparison figure shows the high correlation between the two simulation and measurement data. The Elevation and Azimuthal radiation pattern diagrams for the frequencies 0.775, 3.30 and GHz are shown in Figure From the Elevation diagram at f=0.775 GHz,radiation pattern forms in upper hemisphere. In azimuthal direction, it forms in full area as circular shape. (a)

21 21 (b) Figure 5.28: Radiation pattern at 3.30 GHz (a) Elevation angle (b) Azimuth angle For the resonant frequency GHz Elevation diagram,pattern shrinks in upper hemisphere. In azimuthal direction, it forms in area as octet shape. (a)

22 22 (b) Figure 5.29: Radiation pattern at GHz (a) Elevation angle (b) Azimuthal angle From the frequency f=4.185 GHz Elevation diagram, pattern forms in top upper hemisphere. In azimuthal direction, it forms in area as octet circular shape. Microstrip fractal in stacked structure has been proposed on low cost FR4 substrate. Figure 5.30: Geometry of hexagonal fractal stacked with meander antenna The proposed stacked antenna is simulated and its performances are measured and shown in figure The reflection coefficient, VSWR and directivity by simulation are acceptable in the resonant frequencies. The fractal design is compared with the design without any fractal. The research results show that the improvement in bandwidth as a useful antenna for multi band applications. Multi band performance by the antenna is the outcome

23 S11 (db) 23 from this research work. This work may be useful in wireless communication applications. Even though many multi band structures are already presented by the researchers, this work gives high directivity of db and low fringe effect. In figure 5.31, Hexagonal fractal stacked with meander antenna Radar plot showing the simulated and measured radiation pattern. Simulation Measurement Figure 5.31: Radar plot of hexagonal fractal stacked with meander That the 10 db return loss bandwidth of multiband operation from reflection coefficient vs frequency is displayed in the figure Measurement Simulation Figure 5.32: S-Parameter of hexagonal fractal stacked with circular meander

24 SUMMARY Stacking techniques on U-shaped slotted rectangular patch with slots is attempted. Hexagonal patch size of 47.6 mm, 30 mm, fractals, fractal with stack is designed with meandered patch. U-shaped slotted patch gives radiation between 1.70 GHz and 4.45 GHz. Hexagonal patches give multiband radiation between 0.5 GHz and 6 GHz. Hexagonal patch with 47.6 mm side of stack exhibits maximum gain of 6.65 db, Hexagonal patch 30 mm of side of stack provides maximum gain of 5.83 db while hexagonal fractal gives maximum gain of 6.25 db, and fractal with stack gives maximum gain of 7.54 db. Four configurations of stacked U-shaped slotted rectangular microstrip patch, stacked hexagonal shaped patch 47.6 mm and 30 mm with meander antenna, and stacked fractals on hexagonal patch with meander patch are reported in this chapter between the frequencies 0.5 GHz and 6 GHz. It is concluded that by the introduction of stacked techniques on the microstrip patches provide wideband, multi band characteristics. The next chapter proposes the analysis of multi band meandered stacked microstrip patch antenna using fractal and slots.