Synthesis and Analysis of an Edge Feed and Planar Array Microstrip Patch Antenna at 1.8GHz

Synthesis and Analysis of an Edge Feed and Planar Array Microstrip Patch Antenna at 1.8GHz

Neeraj Kumar

Amity Institute of Telecom Engineering and Management, Amity University, Noida, India

A. K. Thakur

Department of Physics, C.

M. Sc. College, Darbhanga, Bihar, India

Arvind Kumar

Amity Institute of Telecom Engineering and Management, Amity University, Noida, India

Abstract

In this paper, a Microstrip Patch Antenna (MPA) at 1.8GHz has been presented. An edge feed MPA and a planar array MPA has been designed. Further analysis has been done to obtain antenna performance parameters and hence, prove its practicability and applicability as an efficient radiating system. Results obtained in terms of radiated fields, gain, directivity, VSWR and return loss shows that the system is well suited for the desired frequency of operations and best suitable candidate for the GSM system applications. Planar array MPA can be used for wireless communication system as it offers gain of 7dBi, radiation efficiency radiating system is 5.085% and having directivity of 13.77dBi.

Keywords- Microstrip Patch Antenna (MPA), Planar Array MPA, GSM application, gain, directivity, radiation efficiency

1. Introduction

   Antenna, a metallic radiating structure has become one of the most important components of any communication system. It plays an important role when it comes to wireless transmission of data or information. So, antenna designers are facing many challenges in designing a suitable antenna system, which can fulfill the growing demand of bandwidth for different multimedia applications, which require high data rate. In this paper, investigation has been done on an edge feed microstrip patch antenna and a multi element planar antenna. Major design problem related to using microstrip patch is the narrow band- width limiting the use of conventional patch as broadband antennas. But, inspite of its drawback, a MPA offers many advantages which make it fit to be

   used for communication systems. MPA is a low cost and easy to fabricate antenna. With the advancement in printed circuits, these antennas can be easily fabricated on circuit board.

   Performance analysis of planar array has been performed; it significantly increases antenna behavior as compared to edge feed MPA. A planar array is formed using when different number of elements (radiators) is placed along grid in a plane. Planar array is also called as a rectangular array.Advantage of selecting planar is that it provides additional variables (parameters) which can be used to control antenna shape and radiationpattern. These arrays are thusefficientlyused and have capability to provide maximum antenna radiation in desired direction. This is achieved by minimizing the side lobes and un- wanted radiations. Applications of planar array include tracking radar, remote sensing, communications and many more.

   Proposed antenna shows good and optimum behavior at the frequency of 1.8GHz. Planar array with high gain, good directivity and radiation efficiency has been synthesized and analyzed.

2. Antenna Theory &Design

   Two different antenna has been designed and analysed. A edge feed microstrip patch antenna (Antenna 1) and a 2 x 2 Planar Array Microstrip Patch Antenna (Antenna 2).Antennas are shown in figure1.

   (a)

   (b)

   11

   (c)

   Figure 1 (a) Top View of Edge Feed MPA (Antenna 1), (b) Side View of Antenna 1 and (c) Top View of 2 x 2 Planar MPA Array

   Differents steps are involved in design procedure of Antenna1. Dimension of the patch antenna for desired frequency, relative permitivity and substrate has been obtained using different conventional equations of the microstrip patch antenna systems. These equations are as follows:

   In these equations, f0, c and h, are central resonant frequency, c is speed of light and h is the substrate thickness.

   Antenna 2 is a 2×2 planar array. Antenna arrays are formed to improve the radiation characteristics of antenna. This is achieved by selection of phase or amplitude distribution between the elements. Radiation pattern of array antenna is control by the phase of the system. In array antenna, a small side lobe level and small half power beamwidth is desired. Elements of an array are kept identical, to make it simpler and cheaper, but not necessarily. Total Filed of array is given by vector addition of the fields radiated by the individual elements. For identical element array, current distribution is found to be same in each of the element but it also depends upon the spacing between the elements. Performance of an array depends upon type of array, displacements between elements, excitation phase and amplitude

   and the radition pattern of the individual element.

   Different antenna design parameters used for antenna array are following;

   (6)

   (7)

   (8)

   Normalized power pattern of the planar array is given by,

   (10)

   Here, AF is Antenna Factor of the antenna. N & M are the number of elements in X & Y direction respectively.Lx& Ly are the length in x- and y- axis. D0 is the directivity of the array antenna.

   Dimensions and parameters used for Antenna 1 and Antenna 2, operating at the frequency of 1.8GHz has been presented in Table 1 & 2 respectively.

   Table 1. Dimensions used for Antenna1

   S. No.	Parameter	Dimension (mm)
   1.	Patch Length (L)	53.59
   2.	Patch Width (W)	65.84
   3.	Matching Line Width(Wm)	1.602
   4.	Matching Line Length(Lm)	31.74
   5.	Feeding Line Width (Wf)	5.052
   6.	Feeding Line Length (Lf)	30.99
   7.	Substrate Height (H)	3.175
   8.	Relative Permittivity(r)	2.2

   Table 2. Dimensions used for Antenna2

   S. No.	Parameters	Dimension (mm)
   1.	Patch Width (Wp)	65.84
   2.	Patch Length (Lp)	54.44
   3.	Line 1 Width (W1)	219.6 µm
   4.	Line 1 Length (L1)	63.22
   5.	Line 2 Width (W2)	970.8 µm
   6.	Matching Line Width (Wm)	1.532
   7.	Matching Line Length (Lm)	31.77
   8.	Patch Spacing in X-direction (Sx)	133.2
   9.	Patch Spacing in Y-direction (Sy)	133.2
   10.	Substrate Height (H)	3.175
   11.	Relative Permittivity (r)	2.2

3. Simulation

   This section presents the simulation results obtained for the proposed designs, Antenna 1 and Antenna 2. Antennas have been modeled and analyzed antenna simulation softwares. Different antenna parameters have been analyzed to obtain the antenna behavior. Figure 2 shows 3D view of the modled antenna.

   Figure 2(a) Modeled Edge feed Microstrip Patched Antenna (Antenna 1)

   Figure 2(b) Modeled 2 x 2 Planar Microstrip Patched Antenna (Antenna 2)

   1. Input Impedance

      Antenna impedance correlates voltage and current which are present at the input of the antenna system. Impedance contains real and imaginary part. These parts have their own significance. Real part gives the value of either power which is being transmitted or being absorbed within the antenna itself and imaginary part signifies the non-radiating power. Both of the proposed antennas are resonating at 1.8GHz because they contain only the real impedance value and have very low imaginary part. Input impedance vs frequency plot of Antenna 1, is shown in Figure 3. Figure 4 shows the 3D simulation plot of far-field of Antenna 2. It is found that antenna is also having only the real part of impedance at 1.8GHz and imaginary value is zero. Line impedance of the system at frequency 1.8GHz is found to be 70.3044 Ohms.

      Figure 3 Input Impedance Vs. Frequency plot of Antenna 1

      Figure 4 Input impedance of Antenna 2 at 1.8GHz.

   2. Return Loss

      Ratio of input to output power is defined as the S- parameters or the reflection coefficient. It is also called as return loss parameters. Proposed antenna is a single port excited device, So, S11 Vs. frequency curve of antenna is shown in figure 5. Antenna resonating at 1.8GHz has bandwidth of 5% at -25dB return loss.

      Figure 5 S11Vs. Frequency plot of proposed Antenna

   3. VSWR

      VSWR stands for Voltage Standing Wave Ratio, and is also referred to as Standing Wave Ratio (SWR). It defines the ability of antenna as a radiator.VSWR of antenna should be real because it is a parameter which indicates the radiating nature of the antenna as well as matching of antenna to the transmission line. So, higher VSWR value indicates

      mismatch of antenna impedance while the smaller value of VSWR indicates good antenna matching. Figure 6 shows the VSWR vs. Frequency curve of proposed antenna. VSWR value is found to be 1.2 at resonating frequency of 1.8GHz.A VSWR, value of 1.2, indicates reflected power of 3% (-20.8dB).

      Figure 6 VSWR Vs. Frequency plot of proposed Antenna

   4. Radiation Pattern

      A radiation pattern defines the variation of the power radiated by an antenna in a desired direction to that of undesired direction. Figure7 (a) presents the gain of the Antenna 1. Maximum gain of system is found to be 5dBi. Figure 7 (b) presents the gain of the Antenna 2 which has a maximum value of 7 dBi at 1.8GHz.

      Figure 7(a) Radiation pattern in terms of Gain for an Antenna 1.

      Figure 7(b) Gain vsFrequency plot of Antenna2

      Figure 7(c) shows the radiation pattern of Antenna 2. Standard spherical coordinates are used, where is the angle measured off the z-axis, and is the angle measured counterclockwise off the x-axis.

      Figure 7(c) Radiation pattern of Antenna 2

      Figure 7(d) E and H plane pattern of Antenna 2

      Radiation pattern in terms of field parameters is shown in Figure7 (d). It shows that H-plane has maximum value in = 900 while E-plane has the

      minimum value in this direction and maximum value in = 00.

      3.5. Directivity

      Directional property of the antenna is given by directivity of antenna. Directivity indicates the peak power radiation in a particular direction to the average power radiated by the antenna in all the direction. Directivity of Antenna 1 is shown in figure 8 (a) and has value of 8.204dBi with radiation efficiency of 0.8% in the direction at 1.8GHz while the Antenna 2 has directivity of 13.77dBi with radiation efficiency of 5.085% at 1.8GHz. Figure 8 (b), presents directivity of Antenna 2.

      Figure 8(a).Directivity of Antenna 1

      Figure8(b). Directivity of Antenna 2

4. Discussion

   Substrates used for the placement of antenna plays an important role;its height affects performance of antenna. Antenna having thicker substrate gives way to surface wave while a thinner one will have more copper loss (metallic loss). In case of edge feed MPA, resonant frequency can be controlled by changing the length of patch parametrically. Patch width affects the bandwidth of the system. High band-width is achieved by a wider patch MPA.

   Fabrication complexity of Antenna 2 is more, than that of Antenna 1 but has advantage over the Antenna 1. Antenna 2 which also resonates at the center frequency of 1.8GHz, same as Antenna 1, but it has good gain and good directivity value as compared to Antenna 1. Radiation efficiency of Antenna 2 is much better than that of Antenna 1.

5. Conclusion

   In this paper two different antenna systems has been synthesized and analyzed. Techniques of improving the antenna performance by incorporating antenna array have been investigated. Observation obtained shows; the array has 28.57% more gain than that of the single element system. Directivity of planar array is increased by 40.42% and radiation efficiency is also moved from 0.8 % (single element

   system) to5.085% (array antenna) in multi-element antenna.

6. Acknowledgment

   Work presented in this paper is a part of project being done for the completion of M. Tech Degree. We are very much thankful to Amity Institute of Telecom Engineering & Management, Amity University, NOIDA for providing essential Lab facilities required to complete the work in time.

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