ISSN (Print) : 0974-6846
Indian Journal of Science and Technology, Vol 9(S1), DOI: 10.17485/ijst/2016/v9iS1/107888, December 2016 ISSN (Online) : 0974-5645
Design and Analysis of Dual Band Circularly
Polarized Stacked Patch Antenna
for GPS Application
P. Satyanarayana1, K. V. Prasad1 and M. V. S. Prasad2
1
Department of ECE, V R Siddhartha Engineering College, Vijayawada – 520007, Andhra Pradesh, India
2
Department of ECE, RVR and JC College of Engineering, Guntur – 522019, Andhra Pradesh, India
Abstract
In communications, antennas are the very important equipments are necessary to generate a communication system.
Antennas are used in several applications like satellite communications etc. The design specifications of the antenna are
considered using the transmission line model and designed with stacked square patches for multiple band operation
with improved impedance matching. The Diagonal feed divides the given field into two orthogonal modes with equal
magnitude and equal phase shift. The feed position is then optimized to attain the small axial ratio necessary to attain
circular polarization at required frequency. The antenna has been designed at two different frequency bands with center
frequencies of 1575 MHz and 1176 MHz. So the dual band circular polarization has been successfully incorporated into
two square patches.
Keywords: Circular Polarization, Stacked Square Patches
1. Introduction 2. Specifications and Designs
In wireless communication field antennas play a very Design procedure for a Microstrip antenna is outlined to
important role. Some of them are parabolic reflector, meet the specified design characteristics. This antenna is
patch antenna, slot antenna and folded dipole antenna, designed for GPS system. Design of the antenna is carried
etc. Every antenna has its own properties and application. out by developing a set of computer programs using
Because of quick development in the field of wireless MATLAB software. Using these computer programs
and satellite communication there has been a large the laborious work in the calculation of the size of the
demand for minimum cost and minimal weight, compact element, coordinates of the printed patch and feed line for
low profile antennas that are capable of providing high antenna is greatly reduced. The dimensions are optimized
performance over a large range of frequencies. Compact using HFSS software and the theoretical results using
Microstrip antennas capable of dual polarized radiation HFSS for return loss, 2-D and 3-D radiation patterns of
are very suitable for applications in Global Positioning the designed antennas are computed and plotted.
Systems (GPS) that demand frequency reuse and
polarization diversity. 2.1 Specifications
One of the frequently used antennas is Microstrip The Microstrip patch antenna with co-axial feed is
antenna in various applications that need circular designed for the set of specifications. These specifications
polarization. This paper deals with the design of a dual are:
band circularly polarized Microstrip antenna that would • Frequency of operation: L1-1.575 GHz and L5-
work in the L1-(1575.42 MHz) and GPS L5-(1176 MHz) 1.176 GHz.
for GPS applications. • Polarization: Circular polarization.
* Author for correspondence
Design and Analysis of Circular Patch Antenna for UWB Applications
• Beam width at 1.175 GHz: 680 (In VP polarization), On substituting C = 3*10^10cm/sec,fr01 = 1.575GHz,
550(HP). εr, relative = 4.08
• Beam width at 1.575 GHz: 330 (In VP polarization), Leff = 30.8 mm
650(HP). • Length Extension (∆L) Calculation
• VSWR : 1.5 dB w (4)
(ε reff + 0.3)( + 0.264)
• Axial Ratio : 4 dB (max) ∆L =0.412 h
• Application : Global Positioning w
(ε reff − 0.258)( + 0.8)
h
System
On substituting h = 2.5 mm, w = 40.22 mm, εr, relative
2.1.1 Dual band Microstrip patch antenna Design = 4.08
Design involves determination of side lengths (L) of the ∆L = 0.4280 mm
Square patches from the knowledge of resonant • Actual length calculation
(5)
frequencies fr01 (in GHz) fr02 (in GHz), ε r , h (in mm). L
L = eff − 2∆L
• The resonant frequencies selected for the design are
fr01 = 1.176 GHz (L1-band) and fr02 = 1.575 GHz (L5- On substituting Leff = 30.8 mm, ∆L= 0.4280 mm
band). L= 29.9 mm for the patch operating at 1.575 GHz.
• Dielectric constant (εr) of Rogers RT/Duroid
6010/6010L M(tm) substrate is 10.2. 2.1.3 Design Procedure for the Top Patch at 1.176
• Height (h) of the substrate is 1.25 mm, specify εr, fr, GHz
h (in mm). • Width Calculation (W)
The bottom patch width of antenna is
2.1.2 D
esign Procedure for Bottom Patch at 1.575 c ε +1 (7)
GHz: W= r
2 f0 2
• Width Calculation (W)
The Width of bottom patch antenna is given by: W = 53.8 mm
• Effective Dielectric Constant ( ε reff ):
k ε + 1 (1)
W = r
2 f0 2 ε +1 ε r −1 h
ε reff = r + (1 + 12 ) −1/ 2 (8)
On substituting k = 3*10^10 cm/sec, fr01 = 1.176 2 2 W
GHz and fr02 = 1.575 GHz, ε r = 10.2 ε reff = 7.1368mm
W = 40.22 mm • Calculation of Effective length ( Leff ):
• Calculation of relative (εr)
Patch is placed in between two substrates, hence Theoretically it should be taken as λ/2. The calculation
calculate the relative εr, of effective length of the Microstrip patch is given by the
εr, relative = 1 (2) Equation:
h1 h2 c (9)
ε r1
+
εr2
L eff
=
2 f 01 ε reff
εr, relative = 4.08 mm Leff
• Calculation of Effective length ( Leff ): =47.77mm
• Length Extension (∆L):
Theoretically it should be taken as λ/2. w (10)
(3)
(ε reff + 0.3)( + 0.264)
c h
L eff
=
2 f 01 ε reff
∆L =0.412
w
(ε reff − 0.258)( + 0.8)
h
2 Vol 9 (S1) | December 2016 | www.indjst.org Indian Journal of Science and Technology
P. Satyanarayana, K. V. Prasad and M. V. S. Prasad
On substituting h = 2.5 mm,W = 40.22 mm, εr, relative
= 4.08
∆L = 0.4347 mm
• Actual Length of Patch Antenna (L)
L= L − 2∆L
eff
(11)
On substituting Leff = 30.8 mm, ∆L = 0.4280 mm
L = 46.9006 mm
• Calculation of Ground Plane Dimensions
The ground plane dimensions for this design would
be given as:
Figure 3.2. Top and side view of stacked patch with
Lg =6h+L (12)
coaxial feed.
Lg = 77.2074
3.1.2 Simulated Return Loss at 1.176 GHz
Above Figure 3.3 shows that simulated return loss for dual
3. Experimental Results band circularly polarized Microstrip patch antenna (L1-
Band and L5-Band). A return loss of -9.5 dB is considered
3.1 R
esults of Dual Band Circularly
for good performance. From the measurement, it can be
Polarized Microstrip Patch Antenna (L1- observed that antenna is resonating at 1.176 GHz and
Band and L5–Band): 1.575 GHz.
3.1.1 Simulated Stacked Patch Antenna Design Name X Y
m40.00 1.1776 -9.2106
XY Plot 5 HFSSDesign1
Curve Info
ANSOFT
(HFSS) dB(S(1,1))
Setup1 : Sw eep
-2.00
Figure 3.1 and Figure 3.2 shows the dual band circularly
polarized Microstrip patch antenna (L1-Band and L5- -4.00
Band). A return loss of -9.5 dB is considered for good -6.00
dB(S(1,1))
performance.
-8.00
m4
-10.00
-12.00
-14.00
1.170 1.172 1.175 1.178 1.180 1.183 1.185 1.188 1.190
Freq [GHz]
Figure 3.3. Return loss plot at 1.176 GHz.
3.1.3 Simulated Return Loss Plot at 1.575 GHz
The simulated return loss for dual band circularly polarized
Microstrip patch antenna (L1-Band and L5-Band) is
shown in Figure 3.4. A return loss of -11 dB is considered
for good performance. From the measurement, it can be
Figure 3.1. Top view of stacked patch antenna. observed that antenna is resonating at 1.575 GHz.
Vol 9 (S1) | December 2016 | www.indjst.org Indian Journal of Science and Technology 3
Design and Analysis of Circular Patch Antenna for UWB Applications
XY Plot 6 HFSSDesign1 ANSOFT
-1.25
Curve Info
-2.50 dB(S(1,1))
Setup2 : Sw eep
Name X Y
m1 1.5752 -11.1366
-5.00
dB(S(1,1))
-7.50
-10.00
m1
-12.50
1.5700 1.5720 1.5740 1.5760 1.5780 1.5800
Freq [GHz]
Figure 3.4. Return Loss at 1.575 GHz.
3.1.4 Simulated Axial Ratio plot at 1.176 GHz
Figure 3.6. Axial ratio plot at 1.575 GHz.
The above Figure 3.5 shows the axial ratio at 1.176 GHz.
At 0 0 (in degrees) the axial ratio is 10 dB. By measuring 3.1.6 Simulated Radiation Pattern at 1.176 GHz
the axial ratio is below 3 dB the antenna is in circularly
polarization.
Figure 3.7. Radiation pattern at 1.176 GHz.
3.1.7 Simulated Radiation Pattern at 1.575 GHz
Figure 3.5. Axial ratio at 1.176 GHz.
3.1.5 Simulated Axial Ratio Plot at 1.575 GHz
The below Figure 3.6 shows the axial ratio at 1.575 GHz.
At 0 0 (in degrees) the axial ratio is 1.5 dB. By measuring
the axial ratio is below 3 dB the antenna is in circularly
polarization.
Figure 3.8. Radiation pattern at 1.575 GHz.
4 Vol 9 (S1) | December 2016 | www.indjst.org Indian Journal of Science and Technology
P. Satyanarayana, K. V. Prasad and M. V. S. Prasad
4. Conclusion 2. Chen M, et al. A compact dual-band GPS antenna design.
IEEE Antennas and Wireless Propagation Letters. 2013
Feb; 12:245–8.
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