Analysis and Design of Rectangular Microstrip Patch Antenna using Fractal Technique for Multiband Wireless Applications

Transcription

1 2016 International Conference on Micro-Electronics and Telecommunication Engineering Analysis and Design of Rectangular Microstrip Patch Antenna using Fractal Technique for Multiband Wireless Applications Narinder Sharma ECE Department, ACET, Amritsar Punjab, India Ramandeep Kaur ECE Department, ACET, Amritsar Punjab, India Dr. Vipul Sharma ECE Department, Gurukul Kangri Vishwavidyalaya, Haridwar Abstract In this paper a fractal technique is used to design the rectangular microstrip patch antenna for multiband wireless applications. FR4 glass epoxy material is used as a substrate material with thickness of 1.6mm and dielectric constant 4.4. The main purpose of this paper is to analyze the effect of introducing the fractals up to 2 nd iterations on the rectangular geometry of designed antenna. Performance of proposed antenna is analyzed on the basis of different parameters such as VSWR, return loss, gain and radiation pattern. Proposed antennas up to 2 nd iterations are fabricated and tested using VNA (Vector Network Analyzer). Simulated and measured results are in good agreement with each other. The proposed antenna is found suitable to deal with different wireless applications such as WiMAX ( ), WLAN ( ) and point to point high speed wireless communication ( ). Keywords- VNA; VSWR; FR4; fractal; microstrip I. INTRODUCTION Wireless communication system uses the microstrip patch antennas for transmitting and receiving the electromagnetic or radio waves. It is used in many applications because of their low cost, low profile and ease of fabrication [1-2]. These antennas are also suffered from various disadvantages such as narrow bandwidth, low efficiency and less gain [3]. Due to development of small/compact devices, the researchers are attracted towards the compact and wide bandwidth of antennas [4]. Now days, there is a need of multiband and wideband antennas [5], for this purpose the microstrip fractal antennas are used [1]. Fractal antenna geometry is used to achieve wide operating bandwidth and reduction in the size of antenna [6]. These antennas are recursive in nature and are appears to be irregular in shape at all the scales of length [7]. Frequency characteristics of fractal antennas are originated by two different properties such as self-similarity and space filling [8]. Self-similarity property is used to hold the duplication in design geometry at several scales to operate in different operating frequencies or multiband operating frequencies [1]. Space-filling property of fractals is used to miniaturize the antenna. There are large number of fractal shapes has been designed by the researchers like Minkowski, Sierpinski, Koch curves, Hilbert curves etc [9]. These geometries have been used for wideband, multiband or to miniaturize the microstrip patch antennas [10]. In this work, we have presented an antenna by using fractal technique on the rectangular geometry of microstrip patch antenna. We have used line feed technique to provide the excitation to the proposed antenna. The antenna is designed up to 2 nd iteration to analyze the performance parameters such as return loss, VSWR, gain and radiation pattern. Detailed design, simulated and measured results of antenna are discussed in this paper. II. ANTENNA DESIGN AND CONFIGURATION The proposed design of antenna consists of rectangular microstrip patch which is called as the basic geometry of proposed antenna. Further, the fractal technique is applied to the rectangular patch geometry to analyze the performance of antenna at different iterations. The substrate used to design the proposed antenna is FR4 glass epoxy with thickness 1.6mm and relative permittivity of 4.4. Resonant frequency used for the proposed antenna is 3.2GHz. The step wise calculations for the proposed antenna are shown below: Step 1: The wavelength of antenna corresponding to the resonant frequency is calculated by the equation as shown below: c c mm fc (1) Where C is the velocity of light ( ) and fc is the resonant frequency of designed antenna. Step 2: The width of the patch and the thickness of substrate as compared to the wavelength must be very small. In this design we use FR4 glass epoxy as substrate with r 4. 4 & h 1. 6mm. Width of patch is calculated by using following equation. C w mm (2) r 1 2 fo /16 $ IEEE DOI /ICMETE

2 Step 3: Effective relative permittivity in the medium is calculated by using equation as shown below. The value of effective dielectric constant must lie in the range of1 reff r. r 1 r 1 h 2 reff w (3) Step 4: The difference in length is calculated by the following equation. Due to fringing effect, electrically the patch is bit bigger as compared to its physical dimensions. w reff 0.3 h L 0.412h 0. 75mm reff w 0.8 h (4) Step 5: Effective length of the designed antenna is calculated by using the equation shown below: c Leff mm 2 fo reff (5) Step 6: Actual length of patch is calculated by following equation. L Leff 2 L mm 1 (6) TABLE I. PARAMETRIC VALUES OF PROPOSED ANTENNA S. No. Parameters Description Values 1. S W Substrate width 45mm 2. S L Substrate length 38.92mm 3. P W Patch width 28.52mm 4. P L Patch length 21.92mm 5. F W1 Feed line width 1mm 6. F W2 Feed line width 3mm 7. F L1 Feed line length 9.89mm 8. F L2 Feed line length 4.89mm The other iterations of proposed antenna have been designed by cutting the fractal slots along the width of the rectangular geometry of patch. Procedure for designing the fractal slots are shown in Figure 2. The length and width of the slots in the 1 st iteration is 1/10 th of the length and width of base geometry respectively. Length and width of the slots designed in the 2 nd iteration of the proposed antenna is 1/20 th of the length and width of base geometry (0 th iteration) respectively. The designing of the slots as shown in Figure 2 are applied at both the sides along the width of base geometry to obtain the 1 st and 2 nd iterations of designed antenna. Final geometry for the 1st and 2 nd iteration of proposed antenna is shown in Figure 3 (a) and (b) respectively. By using the equations from (1) to (6) it has been found that the length and width of the rectangular patch is found to be 21.92mm and 28.52mm respectively. The corporate line feed is used to provide the excitation to the proposed antenna. The basic geometry (0 th iteration) of proposed antenna is shown in Figure 1 and the parametric values of proposed antenna are shown in Table 1. Figure 2. Procedure for designing the fractal slots Figure 1. Basic geometry (0 th iteration) of proposed antenna Figure 3. (a) 1 st iteration and (a) 2 nd iteration of proposed antenna 56

3 III. RESULT AND DISCUSSIONS The results of designed antennas such as return loss, VSWR and gain have been obtained by using HFSS V13 software. To validate these results the three iterations of designed antennas are fabricated and then tested by using VNA (Vector Network Analyzer). Comparison of both the simulated and measured results shows the agreement with each other. The fabricated prototype of three iterations of designed antenna is shown in Figure 4. Figure 4. Fabricated prototype of designed antennas In this paper, we discussed about the performance of proposed fractal antenna up to 2 nd iteration using line feeding technique. The frequency response of the return loss of different configuration of designed antenna, namely the 0 th iteration, 1 st iteration and 2 nd iteration is shown in Figure 5, Figure 6 and Figure 7 respectively. Figure 7. Return loss curve of 2 nd iteration By observing the return loss curve of 0 th iteration, it has been concluded that the simulated antenna works on three resonant frequency bands whereas the measured antenna works on four resonant frequency bands. Similarly, for 1 st iteration simulated and measured antenna works on six and five resonant frequency bands respectively. 2 nd iteration return loss curve shows that the simulated antenna works on seven resonant frequency bands and the measured antenna works on five frequency bands of operation. For all these frequency bands of operations the value of retur - 10dB which is the desired value for an antenna to work efficiently for practical applications. The variations in the simulated and measured results are due to some uncertainty in the substrate electrical property and also due to the reflections from SMA connector. Figure 5. Return loss curve of 0 th iteration TABLE II. Antenna Iterations 0 th iteration 1 st iteration 2 nd iteration SIMULATED AND MEASURED RESULTS OF PROPOSED ANTENNA Frequency (GHz) 3.18, 6.19 and , 4.65, 5.67, 6.40, 7.92 and , 4.54, 5.53, 6.51, 7.92, 8.39 and 9.48 Performance Parameters Return Loss (db) , and , , , , and , , , , , and VSWR 1.04, 1.24 and , 1.42, 1.27, 1.18, 1.03 and , 1.10, 1.69, 1.30, 1.08, 1.21 and th iteration (Measured) 3.16, 6.22, 8.11 and , , and , 1.32, 1.61 and st iteration (Measured) 3.34, 5.59, 6.40, 7.84 and , , , and , 1.22, 1.75, 1.43 and 1.41 Figure 6. Return loss curve of 1 st iteration 2 nd iteration (Measured) 3.43, 4.51, 6.49, 7.93 and , , , and , 1.85, 1.71, 1.43 and

4 The mismatch between the antenna and feed-line is calculated by VSWR (Voltage Standing Wave Ratio), the quantity. Higher the VSWR means more mismatch between feed line and patch of antenna. The simulated and measured VSWR v/s frequency curves of 0 th, 1 st and 2 nd iteration is shown in Figure 8, Figure 9 and Figure 10 respectively. Simulated and measured values of return loss and VSWR for all the iterations are shown in Table 2. and greater than 3dB for an antenna to work efficiently at the desired frequency band of operation. It is also very important for the multiband antenna to calculate the gain at every frequency band. The value of simulated gain for all the iterations of designed antenna is shown in Table 3. It has been observed that at some frequency bands the value of gain is negative and the particular band is not used for the practical applications. 3D gain plot of 2 nd iterations at different frequencies is shown in Figure 11. Figure 8. VSWR curve of 0 th iteration (a) Figure 9. VSWR curve of 1 st iteration (b) Figure 10. VSWR curve of 2 nd iteration Gain is the most important parameter of antenna, which shows the directional capability of antenna. The value of gain at a particular resonant frequency should be positive (c) 58

5 TABLE III. SIMULATED GAIN OF DESIGNED ANTENNAS Antenna Iterations Frequency (GHz) Gain (db) (d) 0 th iteration 1 st iteration 2 nd iteration (e) (f) (g) Figure 11. 3D gain plot of 2 nd iteration of proposed antenna at different frequency bands of operation IV. CONCLUSION A rectangular microstrip patch antenna using fractal technique for multiband wireless applications is designed in this paper. The three iterations of designed antenna is fabricated and the measured results have been compared with the simulated results. Proposed antenna is designed and fabricated using low cost FR-4 glass epoxy substrate. The designed antenna works on different wireless applications due to its multiband characteristics; such as ( ), WLAN ( ) and point to point high speed wireless communication ( ). Antenna iterations show the maximum value of gain 4.71dB, 8.56dB and 6.84dB respectively. REFERENCES [1] 22 nd Iranian Conference on Electrical Engineering (ICEE), pp , [2] Power, Energy, Information and Communication, pp , [3] V. Va geometry on rectangular microstrip patch antenna with DGS for M-health and Emerging Communication Systems (MedCom), pp , [4] V. D. Raj, A. M. Prasad, M. Satyanarayana and G. M. V. Prasad, Conference on SPACES, pp , [5] M. Sahoo and S. S antenna with fractal geometry Power and Computing Technologies (ICCPCT), [6] hexagonal monopole antenna with freque International Conference on Circuit, Power and Computing Technologies (ICCPCT),

6 [7] and RF Conference (IMaRC), pp , [8] T. Landeau, O. Losito, G. Palma, V. Portosi, A. Jouanneaux and F. Prudenzano, , [9] -230, [10] l Patch Conference (LAPC), pp ,