An Aperture Coupled Microstrip Patch Antenna for Application at 7.5GHz

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An Aperture Coupled Microstrip Patch Antenna for Application at 7.5GHz

Mr. Shashank Anil Kharade

Dept. of E&TC Engg.

Dr. B. A. T. University, Lonere, Raigad, Maharashtra, India.

Prof. Sanjay V. Khobragade.

Dept. of E&TC Engg.

Dr. B. A. T. University, Lonere, Raigad, Maharashtra, India

Dr. Ashish Bagwari

Head of dept. of E&TC Engg. Uttarakhand Technical University, Dehradun, Uttarakhand, India.

AbstractThis paper presents design and simulation of work on microstrip patch antenna with aperture coupling for applications at 7.5GHz of C band. This design of antenna consists of two substrates of FR4 (Flame Retardant 4) material with dielectric constant (r)=4.4 and thickness (h)=1.6mm, and there is a rectangular slot at ground plane which is sandwiched between two substrates and unique flower type design on rectangular patch. Ansoft HFSS simulation software is used for designing and simulation of the antenna based on given operating frequency. From the simulation results, the impedance bandwidth of an antenna is obtained form 7.35 GHz to 7.64 GHz (i.e. 290 MHz) at resonant frequency of 7.52 GHz.

Keywords Aperture Coupling, Microstrio Patch Antenna, FR4, HFSS.

TABLE I. COMPARISON BETWEEN DIFFERENT FEEDING TECHNIQUES[6]

Characteristics

Microstrip Line feed

Coaxial Feed

Proximity Coupled Feed

Aperture Coupled Feed

Spurious Feed Radiation

More

More

Minimum

Less

Reliability

Better

Poor due to Soldering

Good

Good

Ease of Fabrication

Easy

Soldering & Drilling Needed

Alignment Required

Alignment Required

Impedance Matching

Easy

Easy

Easy

Easy

Bandwidth

2-5%

2-5%

13%

21%

Characteristics

Microstrip Line feed

Coaxial Feed

Proximity Coupled Feed

Aperture Coupled Feed

Spurious Feed Radiation

More

More

Minimum

Less

Reliability

Better

Poor due to Soldering

Good

Good

Ease of Fabrication

Easy

Soldering & Drilling Needed

Alignment Required

Alignment Required

Impedance Matching

Easy

Easy

Easy

Easy

Bandwidth

2-5%

2-5%

13%

21%

  1. INTRODUCTION

    In recent few years, the development in wireless communication systems have caused microstrip patch antenna very popular due to their attractive features like light weight, planar profile, ease of analysis and fabrication using modern printed circuit technology [1]. The aperture coupled feeding technique was first introduced by D. M. Pozar and has been used for feeding microstrip antennas widely since it provides advantage of isolating spurious feed radiation by using common ground plane.[2] Generally, Microstrip antennas are fed by using various feeding techniques like microstrip line feed (Inset feeding), coaxial (Probe) feed, proximity coupled feed and aperture coupled feed [3].

  2. FEEDING TECHNIQUES

    There are various ways to feed the microstrip antenna, some popular of them are described here.

    Fig. 1: Different types of Feeding Techniques

    From table I shown above, we can say that Aperture coupled method is better than other feeding methods. Results of Aperture coupled feeding and Proximity coupled feeding (i.e. Non-contacting techniques) are better than that of Microstrip line feeding and Coaxial feeding (i.e. Contacting techniques) in terms of Return loss (S11), VSWR and Gain [5]. The basic disadvantage of using microstrip line feeding technique is spurious feed radiation and Coaxial Feeding is difficult to model and it gives narrow bandwidth. Proximity coupled feeding is better only if gain is primary issue to design an antenna but aperture coupled feeding is more efficient to improve performance of an antenna without reflection in the system [6].

  3. APERTURE COUPLED MICROSTRIP PATCH ANTENNA

    Figure 2 shows the structure of microstrip patch antenna with aperture coupled feeding technique.

    Fig. 2: Design of an Aperture Coupled Microstrip Patch Antenna

    Figure 2 shows the structure of microstrip patch antenna with aperture coupled feeding technique, which consists two dielectric substrates, where ground plane is sandwiched between two substrates. A patch is printed on the dielectric substrate which is above the ground plane and the feed is printed on the dielectric substrate which is below the ground plane. There is slot or aperture is made on the ground plane through which radiating patch and microstrip feed are coupled electromagnetically.

  4. ANTENNA STRUCTURE AND DESIGN

    The proposed design of an aperture coupled microstrip patch antenna is as shown in fig. 3.

    1. (b)

      (c)

      Fig. 3: Proposed design of an aperture coupled microstrip patch antenna;

      1. Patch; (b) Ground Plane; (c)Microstrip Feed Line;

        1. (b)

          Fig. 4: Antenna after Fabrication; (a)Top view; (b)Bottom view

          For designing an aperture coupled microstrip patch antenna for 7.5GHz resonant frequency following parameters were used.

          TABLE II. DESIGN PARAMETERS

          Sr. No.

          Parameter

          Dimensions

          01

          Length of patch (Lp)

          38mm

          02

          Width of patch (Wp)

          29mm

          03

          Length of Substrate (Ls)

          47.64mm

          04

          Width of Substrate (Ws)

          39.04mm

          05

          Length of Feed (Lf)

          27.32mm

          06

          Width of Feed (Wf)

          4mm

          07

          Length of Aperture (Lap)

          1mm

          08

          Width of Aperture (Wap)

          10mm

          09

          Substrate Material

          FR4

          10

          Height of Substrate (H)

          1.6mm

          11

          Dielectric Constant of Substrates (r)

          4.4

          12

          Resonant Frequency (Fr)

          7.5GHz

  5. RESULTS

Ansoft HFSS simulation software is used for designing and simulation of the antenna based on given operating frequency. Fabricated antenna is tested on Vector Network Analyzer (VNA) at Terna College of Engineering, Nerul.

  1. Return Loss (S11) Plot:

    For better performance the return loss and bandwidth of the antenna should be maximum. Following fig. 4 shows the simulated and fabricated return loss plots of proposed antenna design.

    (a)

    Fig. 5: ReturnLoss (S11) Plot; (a)Simulated (b)Fabricated

    TABLE III. RETURN LOSS (S11): SIMULATED VS FABRICATED

    Simulated

    Fabricated

    Frequency (GHz)

    Return loss (dB)

    Bandwidth (MHz)

    Frequency (GHz)

    Return loss (dB)

    Bandwidth (MHz)

    4.82

    -17.454

    200

    7.5

    -43

    300

    5.08

    -15.707

    220

    7.52

    -54.517

    290

  2. Voltage Standing Wave Ratio (VSWR):

For better performance VSWR should be between 1 and 2 (i.e. 1<VSWR<2). Following fig. 5 shows the simulated and fabricated VSWR plots of proposed antenna design.

(a)

(b)

Sr. No.

Simulated

Fabricated

Frequency (GHz)

VSWR

Frequency (GHz)

VSWR

1

4.82

1.3096

7.5

1.004

2

5.08

1.3921

3

7.52

1.0038

Sr. No.

Simulated

Fabricated

Frequency (GHz)

VSWR

Frequency (GHz)

VSWR

1

4.82

1.3096

7.5

1.004

2

5.08

1.3921

3

7.52

1.0038

Fig. 6: VSWR Plot; (a)Simulated (b)Fabricated TABLE IV. VSWR : SIMULATED VS FABRICATED

C. Smith Chart:

Following fig. 6 shows the simulated and fabricated Smith Chart plots of proposed antenna design at 50 impedance.

(a)

(b)

Fig. 7: Smith Chart; (a)Simulated (b)Fabricated

CONCLUSION

An aperture coupled microstrip patch antenna having resonant frequency of 7.5 GHz, return loss of -43dB and bandwidth of around 300 MHz has been designed according to design specifications using Ansoft HFSS simulation software. The antenna is fabricated using FR4 material having dielectric constant (r) 4.4 and height (h) 1.6mm. The antenna is tested using Vector Network Analyzer (VNA). Further this antenna can be useful for C band applications.

ACKNOWLEDGMENT

I would like to express thanks to my Professor Mr. Sanjay V. Khobragade for his guidance and valuable suggestions. I would also like to express my gratitude to Dr. Sanjay L. Nalbalwar, Head of Electronics & Telecommunication Engg. department, Dr. Babasaheb Ambedkar Technological University for continuous support & encouragement during this work and allowing me to use college facilities.

REFERENCES

  1. Girish Kumar, K. P. Ray, Broadband Microstrip Antennas 2003.

  2. T. Uma Maheshwari, Aperture coupled rectangular microstrip patch antenna for S-band applications IOSR-JECE, Ver II May-June 2017

  3. Meryl Lopes, Amita Dessai, Design of Frequency Reconfigurable Microstrip Patch Antenna for Wireless Applications, March 2007.

  4. David M. Pozar, A Review of Aperture Coupled Microstrip Antennas: History, Operation, Development, and Applications University of Massachusetts, Amherst, May 1996

  5. Mohsen Jafari Chashmi 1, Hadi Ghobadi, Design and Fabrication of Aperture Coupled Microstrip Increased Bandwidth Antenna Shahid Beheshti University (SBU), Tehran, Iran Oct. 2015.

  6. Sourabh Bisht1, Shweta Saini, Study the Various Feeding Techniques of Microstrip Antenna Using Design and Simulation Using CST Microwave Studio, IJETAE, Volume 4, Issue 9, September 2014

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