A comprehensive comparative study of
Bandwidth enhancement of an antenna by
non contacting feed lines with Rectangular
Microstrip Patch (RMP) using superstrate
at ku band
POORNANAND DUBEY
Department of Electronics & Communication Engineering, Jabalpur Engineering College, Jabalpur,482011
SUNIL KUMAR SINGH
Department of Electronics & Communication Engineering, Jabalpur Engineering College, Jabalpur,482011
Abstract :
So far as this paper is concerned, this paper presents a comparative study of a rectangular Microstrip patch antenna at Gigahertz (GHz) frequency using non contacting microstrip feed lines of length 14 to 14.9 mm (we didn’t extend the feed line up to 15mm length as in this case it would start contacting with the patch) with superstrate. This means we created capacitive coupling between patch and feed line by varying the length of feed line up to which it doesn’t come into contact with the patch. The results presented here are obtained using Ansoft High Frequency Structure Simulator (HFSS) 11.0 software which is based on full wave finite element method. As a matter of fact, here five different feed line lengths antennas outcomes are shown and their comparative results are also shown in the tabular form. In this study a superstrate of thickness 5mm is also introduced to get the more precise results. Here it is very important to mention that the best performance of antenna i.e., below -10dB that we achieved at the feed line length of 14.9 mm i.e. spacing between the feed line and patch is 0.1 mm and we got bandwidth of 41.5% and resonance frequency of 17.8 GHz at solution frequency of 17.8 GHz.
Keywords: Rectangular patch; Superstrate; Ansoft HFSS; Microstrip feed line
1. Introduction
The environmental factors like raining and thundering are the major part of our functionality as they can create the adverse affect over the antenna and can deteriorate the performance of antenna; particularly its resonance frequency/bandwidth wherever they are used for long duration. This is one of the reasons why superstrate (cover) are often used to protect microstrip antenna. So in a Nutshell it can be said that superstrate not only plays a main role in return loss and bandwidth enhancement but also protect antenna from these natural calamities. Now this paper continues in the following manner: Section 2 extensively presents the formulae for the design and the design of antenna. Section 3 shows the simulated results and in section 4 we will conclude our work with its applications.
2. Simulation Models of Desired Antenna Configuration
The desired Microstrip patch antenna consists of a rectangular patch and different lengths of feed line. In this designing configuration we only vary the length of feed line. We kept the dimensions of substrate, superstrate, ground plane, patch and boundary as it is in every case. The dimension of ground plane and substrate is 64mm ×74mm with substrate having thickness of 3mm. The substrate is having material of FR4_epoxy with dielectric constant εr =4.4 & dielectric loss tangent tan δ= 0.02. Dimension of rectangular patch is 26mm×38mm. Simultaneously we used feed line of dimension of length 14mm, 14.3mm, 14.5mm, 14.7mm and 14.9mm with the constant width of 1.25mm in all five configurations. A superstrate of thickness 5mm is also used above the patch.
To get ourselves more concerned with the design we are showing the following formulae that we used for the determination of dimensions of Substrate, Patch and ground plane.
.
2.1. Rectangular microstrip patch antenna design formulae
Dimensions for Patch :
Width of the patch (W) :
W
Where c is speed of light fo is solution frequency
εr- Relative Permittivity of dielectric
Length of the Patch (L) :
L = Leff - 2 ΔL
where Leff is the effective length of patch Δ L is the length extension for patch
Ground plane dimensions :
Length of ground plane :
Lg = 6h + L
Width of the ground plane :
Wg= 6h +W
*100... (i)
... (ii)
We calculated all the parameters by using the above mentioned formulae.
2.2. Rectangular microstrip patch antenna design
This design is widely representing the view of our antenna from which we obtained the Rectangular plot and VSWR plot.
3.Results and Discussions
Now we are going to show the combined return loss plot and combined VSWR plot of all the antennas in the following manner. All the five antennas with different feed line lengths and the superstrate used in every case. To get more acquainted with these results we are also representing the results in the tabular form as well.
3.1. Tabular Representation for all the feed lines
Solution Frequency- 17.8GHz
Resonance Frequency-17.8GHz (obtained)
S.No.
Feed Line
Length
Return
Loss
VSWR
Bandwidth
1.
14mm -23dB
1.14
16.29%
2.
14.3mm -25dB
1.13 28.3%
3.
14.5mm -34dB
1.06 29.9%
4.
14.7mm -33dB
1.04 32%
Thus after observing the tabular representation it may be said that we are getting maximum bandwidth of 41.5% and VSWR of 1.01 with the feed line length of 14.9mm.
3.2. Combined Return Loss Plot
To get a crystal clear view of all the results we have created a superimposed rectangular plot of all the antenna designs which is showing a resonance frequency of 17.8 GHz in every case. The combined Rectangular plot for all the antennas is as follows. It is also showing the feed line point values in the plot for easier understandability.
3.3. Combined VSWR Plot
This plot is extensively representing the combined VSWR plots for all the antennas. In the graph the feed line lengths (14,14.3,14.5,14.7,14.9 mm) of all the antennas are also mentioned so that every plot can be differentiated with the other.
12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00
Freq [GHz] -35.00 -30.00 -25.00 -20.00 -15.00 -10.00 -5.00 Y1
Ansoft Corporation XY Plot 1 HFSSDesign1
Curve Info dB(S(LumpPort1,LumpPort1))
14.5mm
14.9mm
14mm
14.7mm
14.3mm
12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00
Freq [GHz] 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60 2.80 Y1
Ansoft Corporation XY Plot 4 HFSSDesign1
Curve Info VSWR(LumpPort1) Setup1 : Sw eep1
4. Conclusion
In this manner it may efficiently be concluded that we designed a rectangular microstrip patch antenna with different feed line of non contacting lengths i.e. creating a capacitive coupling between patch and feed line. We obtained five results with different Return losses, VSWRs and percentage bandwidths but out of those five we received maximum bandwidth of 41.5% and vswr of 1.01 at feed line length of 14.9mm i.e. spacing between feed line and patch is of 0.1mm which is also very well evidenced by the return loss plot shown above. We received return losses at resonance frequency of 17.8 GHz which is a part of ku band (12-18 GHz) thus it can be used for satellite communication and broadcasting of television signals.
5. References
[1] K.A. Balanis 2nd Ed:John Wiley and Sons,Inc , Antenna Theory Analysis and Design.,1997.
[2] Wonkyu Choi, Yong Heui Cho, Cheol-Sik Pyo, and Jae-Ick Choi, A High-Gain Microstrip Patch Array Antenna Using a Superstrate Layer ,2006
[3] G.Ramesh, B.Prakash, J.B.Inder, and I.Apisak, “Microstrip Antenna Design Handbook”, Artech House Publishers, Boston,
London,2001
[4] ,*A.B. Mutiara, 2,*R.Refianti, *Rachmansyah , Design Of Microstrip Antenna For Wireless Communication
[5] Mohammad Tariqul Islam, Mohammed Nazmus Shakib, Broadband Microstrip Patch Antenna
