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91
U
Kesava Reddy Jangam1, KNRK Raju Alluri2 & K. Suresh3 Department of ECE, RGU-IIIT, Nuzvid
E-mail : [email protected], [email protected], [email protected]
Abstract - In this paper, a design and analysis of compact coplanar waveguide (CPW) fed rectangular slot antenna is presented. The proposed antenna has simple structure consisting of rectangular slot, placed at the anterior portion of the feed. The overall dimension of the antenna comes around 23mm×24mm×3.2mm and fed by 50Ω coplanar waveguide. The impedance matching and radiation characteristics of the designed structure are investigated by using MOM based commercially available electromagnetic solver IE3D. The simulation results show that the antenna offers excellent performance for X and Ku-band systems ranging from 9.3 GHz to 16.1 GHz with return loss better than -10dB. The impedance bandwidth of the antenna (6.8 GHz) covers about 67.5% of X and 68.3% Ku-band ranges. This antenna configuration would be quiet useful for Satellite, Radar, Terrestrial and Space communications system applications as it is easy to fabricate and integrate with RF circuitry.
Index Terms—CPW Antenna, IE3D, Ku-band, MOM, Satellite, X-band.
I. INTRODUCTION
Modern trends in wireless communications impose the need for design and development of efficient antenna elements, used in products that will eventually operate in contemporary multi-service urban environments, in which several different networks coexists and interoperate. These antennas are necessary to operate either in multi-band mode for specific series.
More ever, the radiating element has to be compact, for easy integration in devices like computers and PDA‟s [1].
An application for lightweight, low-profile antennas with a small footprint has been essential for the increasing use of broadband satellite systems to provide everywhere and high-capacity communication systems that can be installed privately on land vehicles and aircrafts [2]. Antenna technology for satellite and radar applications is an increasingly interesting popular market for mobile satellite terminals. Such systems must be able to receive satellite broadcasting services for maritime, aeronautical or land applications. Current and future multimedia services right demanded for low-cost
high performing terminals. Systems such as satellites, global position system are required to operate at two different frequencies apart too far from each other. CPW antennas can avoid the use of two different single band antennas. The possibility of realizing a compact cost effective full electrically small antenna for automotive tracking applications in X and ku-bands are considered in this study.
In general, the wideband in CPW-Fed slot antenna can be achieved by tuning their impedance value.
Several impedance tuning techniques are also reported in literatures by varying the slot dimensions. For example, these has been carried out in various slot geometries like bow-tie slots, a wide rectangular slot, circular slot, hexagonal slot. The impedance tuning can also performed by using coupling techniques like inductive and capacitive coupled slots, dielectric resonator coupling, and other techniques such as using photonic band gap. Even though large impedance bandwidths could be obtained using these techniques, however, they are quite complicated. In planar slot antennas two parameters affect the impedance bandwidth of the antenna, the slot width and the feed structure. The wider slot gives more bandwidth and the optimum feed structure gives the good impedance matching. The CPW-Fed line with various possible patch shapes, such as T, Cross, Forklike, volcano and square is used to give wide bandwidth. If an antenna designed with multiple resonances covers the wide impedance bandwidth [8].
The X and Ku-bands are portions of the electromagnetic spectrum in the microwave range of frequencies ranging from 8 GHz to 12 GHz & 12 GHz to 18 GHz respectively [3]. The X and Ku-bands are primarily used for satellite, radar, space and terrestrial communications particularly for electron paramagnetic resonance (ERP) spectrometers (9.8 GHz), amateur radio (10 – 10.5 GHz), traffic light detectors (10.4 GHz), amateur satellite (10.45–10.5 GHZ), motion detectors (10.525 GHz), Fixed Satellite Service (11.7-
ISSN (Print): 2278-8948, Volume-2, Issue-5, 2013
92 12.2 GHZ in the U.S.), Ku satellites in Direct Broadcast Satellite (DBS) service (12.2-12.7 GHz in the U.S.), [4].
In this paper, we studied the wheel shape CPW- Fed antenna for X and Ku-band range applications. The proposed antenna coverage frequency band is between 9.3 GHz to 16.1 GHz. This antenna is designed on RT Duroid substrate with thickness of 3.2 mm and dielectric constant (ɛr) of 2.2. The Bandwidth of this antenna defined as the frequency range in which the return loss of the antenna is less than -10 dB and which is 6.8 GHz.
The voltage standing wave ratio of the proposed antenna is 1.17 which is less than or equal to 2 (VSWR ≤ 2).
The simulation software used for this analysis is IE3D which is based on Method of Moments (MOM) electromagnetic solver.
II. ANTENNA DESIGN
The structure of the antenna is shown in Fig 1. The parameters „W1‟ and „L1‟ are the width and length of the rectangular slot, „a‟ and „b‟ are the sides length of the wheel shape patch, „W‟ and „L‟ is the width and length of the antenna respectively. „G‟ is the ground gap and „h‟ is the height of the dielectric substrate from the ground plane. In this study, a dielectric substance (RT Duroid) with thickness of 3.2 mm with a relative permittivity of 2.2. The CPW feed is designed for a 50Ω characteristic impedance with fixed 2 mm feed line width and 0.5 mm ground gap. The proposed antenna produces wide impedance bandwidth with omni- directional radiation pattern. The wide bandwidth and wide impedance matching with reduced size of the antenna is achieved due to resultant of different surface magnetic currents of the structure [7-11].
Fig. 1 : Geometry of the proposed CPW-fed rectangular slot antenna
TABLE I. optimal parameters of the proposed antenna
Parameter Description Optimal value
W Width of the antenna 23mm
L Length of the antenna 24mm
W1 Width of the rectangle slot 2mm
L1 Length of the rectangular slot 17mm a One side width of the wheel
shape patch 3mm
b Another side width of the wheel
shape patch 2mm
ɛr Dielectric constant of RT Duroid 2.2mm
G Ground gap 0.5mm
h Height of the dielectric substrate
from the ground plane 3.2mm III. SIMULATION RESULTS AND ANALYSIS
The antenna performance was studied by the commercially available MOM based simulation software: IE3D EM simulator [14]. The simulated return loss of the proposed antenna is depicted in Fig 2.
The graph shows the maximum return loss of -22 dB at the resonant frequencies of 9.67GHz. The graph also depicts that below -10dB the single layer antenna attained the bandwidth of 6.8 GHz from 9.3 GHz to 16.1 GHz.
The smith chart of the proposed antenna is shown figure 3. It can be observed from the result that the impedance value is 47.39-j7.48Ω for resonant frequency 9.67 GHz, which shows considerable impedance matching between line impedance and antenna impedance.
The voltage standing wave ratio (VSWR) of the proposed antenna is shown in figure 4. It can be observed from the result that the VSWR value is 1.17 for resonant frequency 9.67 GHz, which considered as suitable for the antenna and which gives the VSWR less than or equal to 2 (VSWR≤2).
Fig. 2 : Return loss of the proposed antenna design
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93 Fig. 3 : Smith chart of the proposed antenna design
Fig. 4 : VSWR of the proposed antenna design
The maximum gain, directivity and radiation efficiency of the proposed antenna is 6.124, 9.52, 0.6691 which is shown in fig5, fig6, fig7 respectively. These results are satisfied following relation approximately [12], [13].
Gain ~ Directivity × Radiation efficiency i.e. 6.124 ~ 6.36
Fig. 5 : Gain of the proposed antenna design
Fig. 6 : Directivity of the proposed antenna design
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Fig. 7 : Radiation efficiency of the proposed antenna design Figure 8 and 9 shows the radiation pattern of resonance frequencies at 9.56 GHz. It can be easily observed from the radiation pattern that the designed antenna produces directional radiation and almost stable radiation pattern throughout the whole operating band.
There are some significant advantages if a patch antenna has stable and symmetrical radiation pattern. One of the major advantages is that during construction of an antenna array, the radiation pattern would be more stable across the operating bandwidth
Fig. 8 : Elevation pattern gain display of the proposed antenna design
Fig. 9 : Azimuthal pattern gain display of the proposed antenna design
IV. EFFECT OF SLOT WIDTH „W1‟
For the fixed values of „W‟, „L‟, „h‟, „ɛr‟ and „L1‟
of the proposed antenna the slot width („W1‟) of the wheel shape patch can be varied as 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm and 2.5mm and the simulation results are displayed in Fig.10. The response clearly brings out that the radius affect the return loss of the antenna and it gives different range of frequencies in the same bands (X and Ku- bands). The results for different slot width values of the wheel shape patch CPW antenna is shown in the Table II. It is found that the optimal slot width of the antenna is 2.0 mm.
Fig. 10 : Simulated return loss for different slot width „W1‟
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95 TABLE I. SIMULATED RESULTS FOR DIFFERENT SLOT
WIDTH „W1‟
Width in (mm)
Frequency bands (GHz)
Return Loss (dB)
VSWR Gain (dBI) 0.5
9.6 – 10.5 -16 1.3 6.4
15.3 – 16.8 -17 1.3 4.5
1
9.4 – 10.9 -20 1.2 6.2
14.0-16.3 -27 1.0 4.8
1.5
9.3-11.5 -22 1.1 5.8
13.3-16.2 -43 1.0 5
2 9.3-16.1 -22 1.17 6.124
2.5
9.3 – 10.0 -15 1.4 6.3
10.9 – 13.0 --28 1.0 5.9
V. CONCLUSION
In this paper, a simple new antenna structure has been proposed to execute X and Ku-band range applications with minimal antenna size and better impedance matching. The wheel shape patch structure with rectangular slot, which acts as a tuning stub is introduced at the anterior portion of the feed to enhance the coupling between the slot and feed. With the above structural features the overall dimension of the proposed antenna configuration comes around 23mm×24mm×3.2mm. Good results have been found at X and Ku-band frequencies. The antenna is nominated to be applied for the satellite, radar, space, terrestrial communication applications like broadcasting satellite services for maritime, aeronautical or land applications, amateur radio, motion detectors etc. The proposed antenna can be easily fabricated and place on the small devices due to its smaller dimension and available material.
VI. REFERENCES
[1] Emad S. Ahmed, “Multiband CPW-Fed Rectangular Ring Microstrip Antnna Design for Wireless Communications,” 2011 IEEE Jordan Conference on Applied electrical Engineering and Computing Technologies (AEECT), 978-1- 4577-1084/11 © 2011 IEEE.
[2] H. Parikh, S.V. Pandey and M. Sahoo, “Design of a Modified E- Shaped Dual band patch Antenna for Ku band Applications,” Communication Systems and Network Technologies, 2012 International Conference on May 2012.
[3] Y. Dong, “Planar Ultra- Wideband antennas in Ku- and K- Band for Pattern or Polarization Diversity applications,” IEEE Transactions on Antennas and Propagation, vol.60, No.6, June 2012.
[4] B. Stec, A. Jeziorski, M. Czyzejski and A.
Slowik, “Multi element Patch Antenna for K- Band,” IRS 2012, 19th International Radar Symposium, may 23-25, Warsaw, Poland.
[5] Xu Feng, Chen Xu and Wang Xin‟an, “K- Band Microstrip Antenna Array Applied in Anti- Collision Radar,” communication Technology, 2010 12th IEEE International Conference on Nov.
2010.
[6] N. Misran, M.T. Islam, N.M. Yusob and A.T.
Mobashsher, “Design of a Compact Dual Band Microstrip Antenna for Ku- Band Applications,”
International Conference on Electrical Engineering and informatics 5-7 August 2009, Selangor, Malaysia.
[7] J. William and R. Nakkeeran, “A Compact CPW- Fed UWB Slot Antenna With Cross Tuning Stub,” Progress In Electromagnetics Research C, vol. 13, 159-170, 2010.
[8] J. William and R. Nakkeeran, “Heuristic Design of CPW- Fed UWB slot Antenna,” International Conference on Control, Automaton, Communication-2009, 4th – 6th June 2009.
[9] Y.-F. Lin, P.-C. Liao, P.-S. Cheng, H.M. Chen, C.T.P. Song and P.S. Hall, “CPW- Fed Capacitive H- Shaped Narrow Slot Antenna,”
Electronics Letters, vol.41 No .17, 18th August 2005.
[10] Guo-Chao Wang and Jia-Dong Xu, M. Hirano,
“Novel Application of CPW in antenna Design for Dual-Frequency operation,” Progress In Electromagnetics Research Symposium Proceedings, Cambridge, USA, July 5-8, 2010.
[11] Z. Li, C.-M. Wang, and W.-R. Su, “Designs on CPW- Fed aperture Antenna for Ultra Wideband Applications,” progress In Electromagnetics Research C, vol. 2, 1-6, 2008.
[12] Pramod Dhande, “Antenna and its applications,”
DRDO Science Spectrum, March 2009, PP 66-78
© 2009, DESIDOC.
[13] Constantine A. Balanis, “Antenna Theory – Analysis and Design,” John Wiley and Sons.Inc., NY, USA, 1997.
[14] IE3D 12, Zeland Software, Ins., Fremont, USA
