DESIGN OF MICROSTRIP PATCH ANTENNA FOR 2.45GHz WIRELESS APPLICATIONS

Transcription

1 DESIGN OF MICROSTRIP PATCH ANTENNA FOR 2.45GHz WIRELESS APPLICATIONS P.Swathi 1, N.Nazeeya Anjum 2 1 PG Scholar, Department of Electronics and Communication Engineering, Sri Sai Ram Engineering College. 2 Assistant Professor, Department of Electronics and Communication Engineering, Sri Sai Ram Engineering College. Abstract - Microstrip patch antennas are widely used in modern day communication devices due to their light weight, low cost and ease of fabrication. In this paper, we have designed a Microstrip Patch Antenna and array of patch for 2.45GHz for Wireless Local Area Network (WLAN) applications using antenna simulation software. The designed antenna consists of rectangular radiating patch on FR-4 (lossy) substrate and is excited by the microstrip feeding technique. The resonant frequency of antenna is a function of the dimension of the patch, the permittivity of the substrate and its thickness. Also the antenna characteristics such as efficiency, directivity, gain and resonant frequency parameters are measured. The main objective of this project is to develop the antenna that has high gain, directivity, wide bandwidth and higher efficiency.comparative study between microstrip patch and patch array antenna has been undergone. The patch array also has a better directivity than the single patch The obtained result shows that the proposed antenna operates in ISM frequency band and is characterized by its strong adaptive characteristics for applications around 2.45GHz. Furthermore, the radiation pattern of antenna is directional with a few low spurious radiations. Keywords: Array,CST simulator,ism band,microstrip Antenna. I.INTRODUCTION An antenna is a electrical conductor or a system of conductors or a combination of dielectric and conducting system which can radiate electromagnetic energy into space and receive electromagnetic radiation from space. Antennas are the basic and most important unit in almost all wireless applications. Patch antennas are widely used in modern wireless communication systems because of light weight, high gain, low profile, low cost and ease of fabrication. There are number of substrates that we can use for the design of microstrip antenna. For e.g. Alumina, FR4, RT-duroid etc whose dielectric constants vary in the range of 2.2 to 12. For good antenna performance, a substrate with low dielectric constant is needed in order to provide better efficiency. The microstrip feed line method is used for feeding the patch antenna because of its impedance matching capability. The patch antennas are mostly used in satellite, radar, GPS and GSM communication systems. II. ANTENNA DESIGN The main objective is to design small size patch antenna for wireless applications. The substrate used for the antenna design is FR-4 ( Ɛr =4.3) dielectric material because of its moderate dielectric permittivity. The height of the dielectric material is chosen to be 1.6mm which is the default size of FR-4 material. The width of the conducting patch element is 36mm and length is 30mm for the frequency of 2.4 GHz. The most important 113

2 element is feeding the strip for connecting the probe to the antenna, for which microstrip feed line method is used for better impedance matching. The strip has a width of 3mm and length of 4 mm, which is attached to the rectangular patch antenna as shown in fig 1. Fig 2 Return loss Fig 1 Rectangular patch antenna III.FEEDING TECHNIQUE The feed line to the patch antenna is in its origin. The feed line width is smaller than the patch and is etched directly to the edge of the patch so that power is transferred from the source through a coaxial cable, into the feed line and then to the patch. The purpose of the feed line is to match the impedance from the patch without any additional matching component, however because the feed line is a patch itself it can cause radiation interfering with the patch which will decrease the bandwidth of the antenna. When designing the feed line, this must be along the side of the length, as the current flow is along the direction of the feed wire and at the length is where the maximum radiation of the patch is created. IV.SIMULATION RESULTS Present antenna design simulation is done using CST Software. The response curve for the S11 parameter is shown: After simulation the results shows that given antenna resonate at the expected frequency of 2.4 GHz in fig.2 VSWR is also one of the important characteristics of antenna, it indicates better matching of antenna at a given frequency band. From figure 3 it seems that antenna has VSWR of 1 at 2.4 GHz. Fig 3 VSWR Directivity is also one of the main factor to be considered while designing a antenna. It is the measure of concentration of radiation in maximum direction

3 The response curve for the S11 parameter obtained from the network analyzer is shown in fig. 6. Fig 6 Network analyzer response VI. ANTENNA ARRAY Fig 4 Directivity plot of antenna V.FABRICATED ANTENNA After obtaining the simulation results, the hardware design of the patch was done and the ouput was verified using network analyzer. The antenna parameters such as return loss, VSWR and directivity etc are also measured which are found to be similar with the simulation results. The fabricated patch antenna is shown in fig.5. An antenna array is a group of radiators or array of antenna elements. By carefully controlling the phase and magnitude of the input signal assigned to each antenna element as well as the number and arrangement of elements in the array, it is possible to steer the radiation pattern in a desired direction with the preferred level of gain. Antenna array provides improved directivity when compared to a single-radiator antenna. The directivity of array is due to the interference effects between individual elements of array, which means that the spatial distribution of the elements as well as phases and magnitudes at each element needs to be tuned for optimal performance. Both the radiation pattern and S-parameters of the array are decided by several factors such as the design of patch element, the arrangement and spacing of the array and feed network. Printed arrays are used in wireless local area networks (WLAN). Fig 5 Fabricated patch antenna 115

4 The directivity obtained in two element array is of dbi which is better when compared to the single element patch. The objective of designing a two element patch is to improve the directivity without much changes in other parameters which is obtained and hence shown in the results. The directivity plot with the radiation pattern is shown in fig.10. Fig 7 Two element array The Fig. 8 shows the S-parameter as a function of frequency. The antenna resonates at GHz with parameter (return loss) value of dB.The high value of the return loss idicates better coupling which leads to higher value of the directivity and gain for the antenna designed. Fig 8 Return Loss Vs Frequency plot of two element array Antenna The VSWR curve for the two element array is shown in fig.9. From the figure, it is clear that the value of VSWR for two element array is 1.26 which provides better impedance matching. Fig 9 VSWR plot for two element array Fig 10 Directivity plot of two element array antenna VII. HARDWARE RESULTS OF ARRAY ANTENNA The two element array antenna is fabricated in the same way as single patch antenna and the results were verified using the network analyzer. Fig. 11 shows the hardware design of the two element array antenna

5 that were taken into consideration including the selection of the substrate, feeding technique, dimensions and also the operating frequency for the performance of the antenna. Also the directivity improvement using antenna array without much changes in other parameters such as VSWR, return loss etc was done. Fig 11 Fabricated design of two element array The return loss curve was verified in network analyzer and found to be similar with the simulation results. The return loss (S11) parameter was obtained at 2.44GHz at 28.87dB which is shown in fig 12. Fig 12 Network analyzer response for two element array VIII. CONCLUSION In this paper, We have designed a 2.45GHz microstrip patch antenna which can be used for wireless LAN applications and various responses have been observed. Various factors ACKNOWLEDGMENT We are grateful to the Head of the Department, Department of Electronics and communication engineering, Sri SaiRam Engineering College, India for providing infrastructure and research laboratory to perform the research. REFERENCES 1. JaswinderKaur, NehaAhuja, andrajesh Khanna, Design of Single Band Rectangular Patch Antenna for WLAN Application, International Conference on Recent Advances and Future Trends in Information Technology (irafit2012) 2. A.K.Jaiswal,Mukesh Kumar, A.K.Jaiswal, RohiniSaxena and Anil Kumar, Design Characterization of Rectangular Microstrip Patch Antenna for Wi-Fi Application, International Journal of Current Engineering and Technology, Vol.4, No.2 (April 2014) 3. Md. MarufAhamed, Kishore Bhowmik, Md. Shahidulla, Md. Shihabul Islam, and Md. AbdurRahman, Rectangular Microstrip Patch Antenna at 2GHZ on Different Dielectric Constant for Pervasive Wireless Communication, International Journal of Electrical and Computer Engineering (IJECE),Vol.2, No.3, June C. A. Balanis, Microstrip Antennas, Antenna Theory Analysis and Design, Third Edition, John Wiley & Sons, pp ,