Effect of Patch Dimensions on The Behavior of Resonant Peaks of A Microstrip Patch Antenna – A Comparative Discussion

Effect of Patch Dimensions on The Behavior of Resonant Peaks of A Microstrip Patch Antenna – A Comparative Discussion

Ankan Bhattacharya

Assistant Professor

Department of Electronics and Communication Engg. Mallabhum Institute of Technology, West Bengal, India

Abstract

In this paper a comparative discussion is presented on the effect of patch dimensions on the behavior of the resonant peaks of a microstrip patch antenna. More specifically, the width of the patch is considered in this case. The patch width is increased sequentially from 10 mm to 100 mm and the behavior of the resonant peaks is studied. The antenna is fabricated on a 60 mil RO4003 substrate from Rogers – Corp with a dielectric constant of

3.4 and loss tangent of 0.002. It has been observed that the number of resonant peaks as well as the number of dips increases gradually as the width of the patch is sequentially increased. The study of this behavior would help us to design a multiband antenna for various applications as well as to choose an optimum patch width while designing an antenna.

Keywords

Microstrip patch antenna, patch width, resonant peaks

1. Introduction

   Microstrip Patch Antennas are popular for low-profile applications at frequencies above 100 MHz (o < 3 m). they commonly consist of a rectangular or square metal patch on a thin layer of dielectric (called the substrate) on a ground plane. The assembly is usually contained inside a plastic radome which protects the antenna structure from damage. Patch antennas are simple to fabricate and easy to modify and customize. Patches may be photo- etched making them adaptive for low-cost, mass production. [1]-[3]

   This paper is mainly concerned about the role of patch dimensions, the patch width in particular on the behavior of resonant peaks and dips – sudden drops of parameter S11 are considered as dips in this study. The conclusion is drawn on the basis of several simulation results in a generalized process along with detailed analysis of each simulation result.

2. Design

   A 10 x 10 mm square patch is designed and simulated in IE3D environment. Let the length and width of the patch be represented as L and W respectively. In this case L = 10 mm and W = 10 mm. Fig. 1 shows the geometrical structure of the designed patch.

   Fig. 1 A 10 x 10 mm square patch

   IE3D provides an user friendly environment for designing patches of various sizes and shapes. Initially, a square shaped patch is designed of dimensions 10 x 10 mm. The width of the patch is increased sequentially from 10 mm to 100 mm in 10 mm intervals and the results are analyzed in sequential steps.

   Fig. 2 S11 vs Frequency plot for a 10 x 10 mm patch

   Fig. 3 S11 vs Frequency plot for a 10 x 20 mm patch

   Fig. 4 S11 vs Frequency plot for a 10 x 30 mm patch

   Fig. 5 S11 vs Frequency plot for a 10 x 40 mm patch

   Fig. 6 S11 vs Frequency plot for a 10 x 50 mm patch

   Fig. 7 S11 vs Frequency plot for a 10 x 60 mm patch

   Fig. 8 S11 vs Frequency plot for a 10 x 70 mm patch

   Fig. 9 S11 vs Frequency plot for a 10 x 80 mm patch

   Fig. 10 S11 vs Frequency plot for a 10 x 90 mm patch

   Fig. 11 S11 vs Frequency plot for a 10 x 100 mm patch

3. Discussion

   S11 is a measure of how much power is reflected back at the antenna port due to mismatch from the transmission line. When connected to a network analyzer, S11 measures the amount of energy returning to the analyzer not whats delivered to the antenna. The amount of energy that returns to the analyzer is directly affected by how well the antenna is matched to the transmission line. A small S11 indicates a significant amount of energy has been delivered to the antenna. S11 values are measured in dB and are negative, ex: -10 dB. S11 is also sometimes referred to as return loss, which is simply S11 but made positive instead (Return Loss = – S11). So if the antenna Return Loss is 8 dB, S11 is -8 dB. The third and final method to measure an antennas ability to accept power is VSWR (voltage standing wave ratio). VSWR evaluates the ratio of the peak amplitude of the voltage of the wave on the transmission line versus the minimum amplitude of the voltage of the wave. A VSWR of 1 is ideal; this indicates that there is no reflected power at the antenna port. When the antenna and transmission line are not perfectly matched, reflections at the antenna port travel back towards the source and cause a standing wave to form. The worse the mismatch, the larger the amplitude of these reflections. [4] A VSWR

   < 2 is acceptable for an antenna. So, values of S11 = – 10 dB are considered as the margin for resonant peaks

   – TABLE I. Values of S11 -10 dB are considered as dips in this study.

   TABLE I:

   Return Loss, S11, VSWR and Reflection Loss [5]

   Return Loss (dB)	S11	VSWR	Reflection Loss (dB)
   3.0	-3.0	5.85	3
   6.0	-6.0	3.0	1.26
   7.0	-7.0	2.6	0.97
   8.0	-8.0	2.3	0.75
   9.0	-9.0	2.1	0.58
   10.0	-10.0	1.9	0.46
   11.0	-11.0	1.8	0.36
   12.0	-12.0	1.7	0.28
   13.0	-13.0	1.6	0.22
   14.0	-14.0	1.5	0.18
   15.0	-15.0	1.4	0.14
   16.0	-16.0	1.4	0.11
   17.0	-17.0	1.3	0.09
   18.0	-18.0	1.3	0.07
   19.0	-19.0	1.3	0.06
   20.0	-20.0	1.2	0.04

4. Simulation result

   Simulation result of 10 x 10 mm patch:

   • Freq: 7.6762 GHz; S11: -13.2335 dB Resonant Peak

     Simulation result of 10 x 20 mm patch:

     Freq: 7.3166 GHz; S11: -08.3908 dB Dip

   • Freq: 7.9252 GHz; S11: -20.9171 dB Resonant Peak

     Simulation result of 10 x 30 mm patch:

   • Freq: 5.5276 GHz; S11: -17.1487 dB Resonant Peak

     Freq: 7.1690 GHz; S11: -06.9580 dB Dip

   • Freq: 9.3268 GHz; S11: -19.2582 dB Resonant Peak

     Simulation result of 10 x 40 mm patch:

     Freq: 4.2551 GHz; S11: -05.5089 dB Dip

     Freq: 7.1045 GHz; S11: -04.1451 dB Dip

     Freq: 8.2202 GHz; S11: -09.2352 dB Dip

   • Freq: 8.4629 GHz; S11: -26.2666 dB Resonant Peak

     Simulation result of 10 x 50 mm patch:

     Freq: 3.4528 GHz; S11: -02.9941 dB Dip

   • Freq: 6.6803 GHz; S11: -17.1321 dB Resonant Peak

     Freq: 7.0123 GHz; S11: -04.3638 dB Dip

   • Freq: 8.0082 GHz; S11: -11.6859 dB Resonant Peak

   • Freq: 9.9907 GHz; S11: -13.3507 dB Resonant Peak

     Simulation result of 10 x 60 mm patch:

     Freq: 2.9180 GHz; S11: -01.9317 dB Dip

   li>

   Freq: 5.6198 GHz; S11: -10.5338 dB Resonant Peak

   Freq: 7.0123 GHz; S11: -02.8889 dB Dip

   Freq: 7.7131 GHz; S11: -07.0749 dB Dip

   • Freq: 8.3032 GHz; S11: -14.7301 dB Resonant Peak

   • Freq: 9.2254 GHz; S11: -28.8576 dB Resonant Peak

   Simulation result of 10 x 70 mm patch:

   Freq: 2.2079; S11: -01.1221 Dip

   Freq: 4.2827; S11: -04.3279 Dip

   Freq: 6.3207; S11: -17.4540 Resonant Peak

   Freq: 6.9661; S11: -02.9146 Dip

   Freq: 7.3903; S11: -05.0589 Dip

   Freq: 8.3586; S11: -22.8527 Resonant Peak

   Freq: 9.6772; S11: -22.4015 Resonant Peak

   Simulation result of 10 x 80 mm patch:

   Freq: 2.2079; S11: -01.1220 Dip

   Freq: 4.2827; S11: -04.3275 Dip

   Freq: 6.3207; S11: -17.4527 Resonant Peak

   Freq: 7.3903; S11: -05.0587 Dip

   Freq: 8.3586; S11: -22.8762 Resonant Peak

   Freq: 9.6772; S11: -22.4205 Resonant Peak

   Simulation result of 10 x 90 mm patch:

   Freq: 1.9590; S11: -00.9197 Dip

   Freq: 3.8217; S11: -03.1475 Dip

   Freq: 5.6475; S11: -16.2659 Resonant Peak

   Freq: 7.2336; S11: -03.4879 Dip

   Freq: 7.4733; S11: -18.8093 Resonant Peak

   Freq: 8.0358; S11: -07.4001 Dip

   Freq: 9.2438; S11: -22.5915 Resonant Peak

   Simulation result of 10 x 100 mm patch:

   Freq: 1.7838; S11: -00.8129 Dip

   Freq: 3.4528; S11: -02.6165 Dip

   Freq: 5.1127; S11: -11.6211 Resonant Peak

   Freq: 6.7541; S11: -11.7924 Resonant Peak

   Freq: 7.2151; S11: -04.2486 Dip

   Freq: 7.8514; S11: -05.6010 Dip

   Freq: 8.3770; S11: -11.8501 Resonant Peak

   Freq: 8.7920; S11: -13.6565 Resonant Peak

   Freq: 9.9815; S11: -14.6177 Resonant Peak

5. Conclusion

   It has been observed from the above study that the number of Resonant Peaks as well as Dips increases in regular proportion with the increase in patch width, which is the point of focus. A proper knowledge of Peaks and Dips are extremely important while designing a multiband patch antenna. We have to opt for chosing an optimum patch width to fulfill our desired requirements since patch width is an obvious issue for mini radiating systems.

6. References

1. John D. Kraus, RonaldJ. Marhefka; Antennas-For All Applications; Fifth reprint 2004 pp. 324

2. Ankan Bhattacharya; Design, simulation and analysis of a Probe Feed Patch Antenna with Benzocyclobutene as the substrate material; International Journal of Science, Engineering and Technology Research (IJSETR) Volume 2, Issue 7, July 2013

3. D. Orban and G.J.K. Moernaut; The Basics of Patch Antennas; Orban Microwave Products; www.orbanmicrowave.com

4. http://antenna- theory.com/definitions/sparameters.php

5. http://info.lsr.com/LSR-Wireless-RF-Design- blog/bid/282190/Terms-Definitions-of-Basic- Antenna-Design-II

6. Radiation from Microstrip Radiators; IEEE Transactions on Microwave Theory and Techniques, April 1969, Vol. 17, No. 4 pp. 235-236

7. Microstrip and Printed Antenna Design; (2nd Edition) Randy Bancroft SciTech Publishing Inc. 2009 page 106

8. John de Kraus, Ronald J. Marhefka; Antenna for all applications (3rd edition) 2002, ISBN 0-07- 232103-2

9. D. C. Nascimento and J. C. da S. Lacava; Design of Low-Cost Probe-Fed Microstrip Antennas; Technological Institute of Aeronautics; Brazil

10. N.T. Markad, Dr. R.D. Kanphade, Dr. D. G. Wakade; Probe Feed Microstrip Patch AntennaComputer Aided Design Methodology; International Journal of Scientific and Research Publications, Volume 2, Issue 5, May 2012 1 ISSN 2250-3153; www.ijsrp.org