Performance Analysis of Different Shapes Patch Antennas At 2.45 Ghz

Performance Analysis of Different Shapes Patch Antennas At 2.45 Ghz

Ms. Rakhi

Electronics and communication Engineering IGIT (GGSIPU)

Kashmiri Gate, Delhi, India.

Ms. Sonam Thakur

Department of Electronics & Communication Engineering IGIT (GGSIPU)

Kashmiri Gate, Delhi, India.

Abstract The area of microstrip antennas is one of the most dynamic fields of antenna theory and has seen some inventive work in recent years. The increasing need for mobile communication and the emergence of newer technologies require an efficient design of antenna of smaller size for wider frequency range applications such as Wi-Max. In this work, different geometry shapes, the E-shape and U-slot are developed from a rectangular patch of the width (W) = 39 mm and length

(L) = 29 mm at a frequency of 2.45 GHz. The proposed antennas are simulated using CST microwave 2011 software and the results are compared with the conventional rectangular patch antenna. Patch antennas resonating at 2.45 GHz are simulated, manufactured and tested. The properties of the antenna such as bandwidth, S parameter, VSWR have been investigated. The substrate material used for the proposed antennas is FR-4 lossy, with the dielectric constant of 4.1.

Index Termsmicrostrip patch antenna, CST, return loss, VSWR.

1. INTRODUCTION

   In wireless communication, there are several types of micro strip antennas, the most common of which is the patch antennas. Microstrip antenna consists of very small conducting patch built on a ground plane separated by dielectric substrate. The microstrip patch antenna offers the advantages of low profile, ease of fabrication, and compatibility with integrated circuit technology. They can be designed to operate over a large range of frequencies (1- 40 GHz) and easily combine to form linear or planar arrays. It can generate linear, dual, and circular polarizations. The microstrip antenna has different feeding techniques like probe fed, aperture coupled, proximity and insert feed. As conventional antennas are often bulky and costly part of an electronic system, the microstrip antenna considered as an engineering breakthrough for compact communication devices and systems especially for remote uses where compactness is much desirable feature. However, conventional microstrip patch antenna suffers from very narrow bandwidth. This poses

   design challenge for the microstrip antenna designer to meet the broadband requirements. The proposed antennas are designed for 2.45 GHz frequency with rectangle patch, E- shape patch and U-slot patch and compared with the

   measured result. The proposed antennas are made by using microstrip feed and simulated on CST microwave 2011. A typical patch antenna is shown in fig 1.

   Fig 1: A typical patch antenna

   Microstrip antenna is a simplest form of antenna configuration. It consists of a radiating patch on one side of dielectric substrate (r10) and it has a ground plane on other side. A microstrip patch antenna consists of a many conducting patch of any planar or nonplanar geometry. The rectangular and circular patches are the basic and mostly common used for microstrip antennas because of ease of fabrication system. The microstrip antenna have various advantages such as small size, low-cost of fabrication process, low profile of antenna, light in weight, ease of installation process and integration with many feed types. The applications of these type of antennas in various fields such as in the medical applications, satellite and of course even in the military systems just like in the rockets, aircrafts missiles

   .However, the microstrip antenna has a low gain and a narrow bandwidth. To overcome its limitation of narrow impedance bandwidth and low gain, many techniques have been proposed. In microstrip patch antenna there are some well- known methods to increase the bandwidth of patch antennas, such as, cutting a resonant slot in the patch, reduced ground plane, the use of thick substrate, the use of a low dielectric substrate, the use of a low dielectric substrate, the use of various impedance matching feeding techniques, the use of slot antenna geometry and multi-resonator stack configurations. However, the bandwidth and the size of an antenna are generally reciprocal conflicting properties that are improvement of one of the characteristics normally results in

   degradation of the other one. Various shapes of cutting slots and slits have been designed on patch antennas to reduce their size. For efficient radiation, the size of microstrip antenna should be /2. If the size reduces less than /2, the radiation efficiency of antenna decreases along with other antenna parameters.

   1. Length of ground

      Lg 6h L

   2. Width of ground

   Wg 6h W

2. DESIGN ANTENNA GEOMETRY

   A proposed Microstrip patch antenna starting with a rectangular patch, substrate and ground plane. These rectangular parameters are simulated to optimize the performance and ending with slotted patch and E-shape patch. The proposed antenna use Microstrip feed line of impedance 50 ohm.

   The proposed antenna has dimensions given below:

   Operating frequency	2.45 GHz
   Dielectric Constant	4.1 FR-4
   Patch Material	PEC
   Length of Patch L	29 mm
   Width of patch W	39 mm
   Substrate thickness, h	1. 5m
   Patch thickness, t	0.1 mm
   Inset-fed gap, Gpf	1 mm

   Table 1: Physical dimensions of proposed patch antennas

   For designing the proposed rectangular microstrip patch antenna the equations are used to calculate the dimensions of antenna. The designed antenna is resonating at 2.45 GHz and simulated results using CST software.

   1. Leff = effective length

      The terms used in these equations are described below: c = speed of light

      fo= resonant frequency h = substrate thickness r = relative permittivity

3. GEOMETRY OF PROPOSED PATCH ANTENNA

   1. Design of rectangular patch antenna

      Inset-fed length, Fi	10 mm
      Feed line length, Lf	24.5 mm
      Feed width, Wf	2.9 mm

      Table 2: Physical dimensions of rectangular patch antenna

      Leff

      2 fo

      c

      reff

      Fig 2: Rectangular patch on CST

   2. Design of U-slot patch antenna

      1. W = width of patch

         W

         2 fo

         c

         Inset-fed length, Fi	10.5 mm
         Feed line length, Lf	25 mm
         Feed width, Wf	2.9 mm
         Slot Length, Ls	7 mm
         Slot Width, Ws	11 mm

         r 1

         2

      2. reff = effective permittivity

         1

         reff

         r 1 r 1 112 h 2

         2 2 w

         Table 3: Physical dimensions of E-Shape patch antenna

      3. L= Change in length

         reff 0.3 W 0.264

         h

         L 0.421h

         reff 0.258 W 0.8

      4. Length of patch

      L Leff

      h

      2L

      Fig 3: U-slot patch on CST

   3. Design of E-shapepatch antenna

Table 4: Physical dimensions of E-Shape patch antenna

Fig 4: E-shape patch on CST

1. SIMULATION & RESULTS

   Microstrip patch antennas are designed for wideband applications using CST as shown in figures. First rectangular patch has been designed and from this keeping the length and width of the patch constant, U-slot and E-shape has been cut. As a result, the frequency of patch shifted. Therefore U-slot and E-shape patches have been optimized for the desired frequency. We have seen that, on changing the Inset-fed length Fi, the frequency of operation changes. Hence, by modifying Fi and feed line length Lf, we optimize the frequency at 2.45 GHz. As a result, all the three patch antennas are working at same frequency with same dimensions, but the return loss, VSWR and gain of the antennas changes.

   Results have been shown below in the table :

   	Rectangular patch	U-slot	E-shape
   Return loss (dB)	-32.36	-28.93	-19.04
   VSWR	1.04	1.07	1.25

   It can be seen after simulation that the return loss degraded if we cut shapes from a rectangular patch without changing its dimensions.

   Return loss and VSWR compared are also shown in the figure below:

   Fig 5: S11 parameter simulated on CST

   Fig 6: VSWR simulated on CST

   All the simulated antennas are fabricated and tested on VNA (Vector Network Analyzer) in laboratory. Experimental results are shown below.

   Fig 7: S11 parameter tested on VNA

   It has been found that the fabricated antennas work well in the given range at the desired frequency.

   Fig 8: Fabricated antennas

2. CONCLUSION

   In this work, the aim was to design different shapes of antenna from a rectangular patch keeping the patch length and width constant, operating at the single frequency. We have selected three different patch antennas and are simulated and fabricated. The simulated results are compared with the conventional microstrip patch antenna. Experimental result shows that the given antennas work well at 2.45 GHz with the bandwidth of 50 MHz. The fabricated antennas can be used for Wimax applications.

3. REFRENCES

1. 1. C. A. Balanis, Antenna Theory, Analysis and Design, John Wiley & Sons, NewYork, 1997.

2. 2. Analysis of Electrical Parameters of Inset Fed Rectangular Micro strip Patch antenna (RMPA), International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 7, July 2013).

3. 3. Design and Characterization of E-Shape Microstrip Patch Antenna for Wireless Communication, International Journal of Advanced Trends in Computer Science and Engineering, Vol.2, No.2, Pages : 177-180 (2013) .

4. 4. Performance Comparison of Micro-strip Antennas with Different Shape of the Patch, International Journal of u- and e- Service, Science and Technology Vol. 6, No. 3, June, 2013.

5. 5. Enhancing the Bandwidth of a Microstrip Patch Antenna using Slots Shaped Patch, American Journal of Engineering Research (AJER) e-ISSN : 2320-0847 p-ISSN : 2320-0936 Volume-02, Issue- 09, pp-23-30.