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Circularly Polarized Microstrip Patch Antenna with Slits
İmeci Ş. Taha, Kızrak M. Ayyüce and Şişman İsmail
Department of Electronics and Communication Engineering
Haliç University, İstanbul, TURKEY
tahaimeci@halic.edu.tr, ayyucekizrak@halic.edu.tr, ismailsisman@halic.edu.tr
Abstract: A compact circular-polarized square microstrip antenna with four slits and a pair of truncated
corners is designed and simulated. In addition, the size reduction of the patch approximately 29% as
compared to the conventional corner-truncated square microstrip antennas at a given operating frequency,
obtained. There is also an analysis of tolerance in order to see possible fabrication errors which includes
different dielectric heights and relative permittivity. Details of the simulation results using a commercial
electromagnetic simulation software called Sonnet software [1], are presented and discussed.
Keywords: Microstrip, patch, antenna, compact, slit
1. Introduction
Traditionally, a single-feed circular-polarization (CP) operation of the corners truncated square
microstrip antenna is extensively used in single patch and array designs [2]. In this work, we obtain the
compactness of the proposed CP design due to inserting four slits of equal lengths at the corners [2]. These
inserted slits at the corners of the square patch result in meandering of the excited fundamental-mode
patch surface current path, which effectively lowers the resonant frequency of the modified square patch
[3]. Details of the proposed compact CP design are described. Moreover, the results of the simulation with
Sonnet software is presented and discussed.
2. Design procedure
The specifications require the right hand side circularly polarized microstrip patch antenna at
2.184 Ghz. More importantly, the physical requirement is to reduce the size of the patch antennas [4]. Two
different types of commercial substrates which are Duroid 5880 (εr = 2.2, h=125mils) and Arlon Cu
233LX (εr =2.33, h=125mils) are chosen. The design procedure of those antennas are followed. First, we
design the conventional corners truncated microstrip patch antennas at 2.184 Ghz. Subsequently, we
designed the proposed antenna which have four slits of the equal lengths at the patch corners to achieve
the size reduction [2]. Geometry of the proposed microstrip antennas is shown in Figure 1 which is
designed with Duroid 5880 (εr = 2.2, h=125mils).
The 50-Ω feeding line has a width 9.89 mm and 10 mm length. All the inserted slits are of length
18 mm and width 1mm along the directions of ±45 degree. The square patch has a side length L=39 mm
and a pair of truncated corners of dimensions 8.5 mm × 8.5 mm [2].
Table 1 discusses different type of microstrip patch antennas in terms of pattern, directivity,
polarization, bandwidth etc.
26th Annual Review of Progress in Applied Computational Electromagnetics April 26 - 29, 2010 - Tampere, Finland ©2010 ACES
754
Table 1. Microwave Planar antenna overview.
Pattern Directivity Polarization Bandwidth Comments
Patch
Broadside Medium Linear/Circular Narrow Easiest
design
Slot
Broadside Low/Medium Linear Medium Bi-
directional
Ring
Broadside Medium Linear/Circular Narrow Feeding
Complicated
Spiral
Broadside Medium Linear/Circular Wide Balun&
Absorber
Bow-Tie
Broadside Medium Linear Wide Same as
Spiral
TSA(Vivaldi)
Endfire Medium/High Linear Wide Feed
transition
Yagi Slot
Endfire Medium Linear Medium
Two layer
design
Quasi Yagi
Endfire Medium/High Linear Wide Uniplanar,
Compact
LPDA
Endfire Medium Linear Wide Balun
Two Layer
Leaky-Wave Scannable High Linear Medium
Beam
steering
Beam-tilting
Fig. 1. 3D View of the antenna.
26th Annual Review of Progress in Applied Computational Electromagnetics April 26 - 29, 2010 - Tampere, Finland ©2010 ACES
755
3. Test and Simulation Results
The simulation results of the return loss is shown in Figure 2. Figure 3 and 4 has the imaginary
and real part of Zin, Figure 5 shows the radiation patterns and finally Figure 6 has the current distribution.
Fig. 2. Return loss for the proposed patch antenna with different dielectric heights.
Fig. 3. Imaginary part of Zin for the proposed patch antenna.
26th Annual Review of Progress in Applied Computational Electromagnetics April 26 - 29, 2010 - Tampere, Finland ©2010 ACES
756
Fig. 4. Real part of Zin for the proposed patch antenna.
Fig. 5. Far field radiation pattern of the antenna.
26th Annual Review of Progress in Applied Computational Electromagnetics April 26 - 29, 2010 - Tampere, Finland ©2010 ACES
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Fig. 6. Current distribution on the antenna.
As it is seen on Figure 2, dielectric height does not affect the results much, but when we changed
the dielectric material (permittivity changed from 2.2 to 2.33) a slight frequency shift occurred. In both
cases return losses at the resonance frequency is satisfactory. Figure 3 and 4 show the imaginary part of
the input impedances, which are close to zero, as expected for the resonant antennas, and the real part of
the input impedances are almost 50 ohm for the 3 different values of the dielectrics. In Figure 5, right-
hand circularly polarized radiation pattern has 5,6 dB gain and left hand circularly polarized radiation
pattern has a value of minus 4,56 dB in polar plot. Figure 6 shows the current distribution on the surface
of the patch.
4. Conclusions
In this work a compact size microstrip patch antenna which has four slits at each corner is
designed, simulated. Slits helped to reduce the antenna dimensions about 29%. The design requirements
are met and simulated results which were discussed on Section 3 are satisfactory. Simulated results with
different parameters show that antenna is tolerant for changes of possible fabrication losses.
5. Acknowledgments
Special thanks are due for Greg Alton from Sonnet software who has promptly issued licenses for
Haliç University.
References
[1] Sonnet Software, version 12.56, www.sonnetsoftware.com, 2009.
[2] M. Gokten, F. Altunkilic, H. Son, “Compact Circularly Polarized Patch Antenna”, Department of
26th Annual Review of Progress in Applied Computational Electromagnetics April 26 - 29, 2010 - Tampere, Finland ©2010 ACES
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Electrical Engineering and Computer Science, Syracuse University, NY, Spring 2002.
[3] R. F. Harrington, Time-Harmonic Electromagnetic Fields, McGraw-Hill, New York, 1961.
[4] E. Arvas, Syracuse University Planar Microwave Antennas Course Notes, New York, Spring 2002.
26th Annual Review of Progress in Applied Computational Electromagnetics April 26 - 29, 2010 - Tampere, Finland ©2010 ACES
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