2017 IEEE 15th Student Conference on Research and Development (SCOReD)
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Compact Multiband Microstrip Patch Antenna with Slot-Rings for Wireless Applications Chandrasekharan Nataraj1 Faculty of Computing, Engineering and Technology Asia Pacific University (APU) Kuala Lumpur, Malaysia
[email protected]
Sathishkumar Selvaperumal3 Faculty of Computing, Engineering and Technology Asia Pacific University (APU) Kuala Lumpur, Malaysia
[email protected] Abstract—This paper presents the design of compact microstrip patch antenna operating at multiple frequency bands. The antenna has traditional structure of microstrip patch combined with two ring slots and two semicircular slots at the edges. The antenna is designed with dimensions of 24.25 x 31.43 x 3.5 mm on a TD/Duroid 6002 substrate having a relative permittivity of 2.94. The antenna has a good bandwidth of 90 MHz (3.17-3.26 GHz) at 3.2 GHz WiMAX technology, 80 MHz (3.55.2.63 GHz) at 3.6 KHz for mobile broadband (MBB) frequency and 465 MHz at range from 4.85-to-5.16 GHz for Wireless Local Area Network (WLAN) (802.11a/h/j/n/ac). The antenna meets the 2:1 VSWR at the selected center frequencies. The designed antenna able to produce a maximum gain of 7.15dB at 4.82 GHz. The antenna has good bandwidth and reasonable efficiency for the wireless communication applications. Keywords— Wireless Personal Area Network; Multiband Antennas; WiMAX; Microstrip Patch; Ring slot.
I. INTRODUCTION (HEADING 1) In the wireless communication based applications, antennas are used as the main terminal device as well as act as a key indicator for deciding performance of the system. An RF antenna is defined as a terminal device which is used to transfer a guided wave into the free space and vice versa. From functional viewpoint, the antenna is principally act as a transducer element that converts alternative pulses into electromagnetic (EM) fields or vice versa. The physical components that make up an antenna structure are called elements. At present, microstrip patch is the most commonly used antenna due to its conformal and simple planar structure. There are different shapes of antennas being considered in the microstrip patch antenna design [1]. For wireless system and RF applications, patch structure considered as one of the most favorite antenna due to compact size design and low cost. In addition, patch antenna has become a focused research area in recent years because of its low profiles, small volumes, good integration and better performance.
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Assia Ali Ismael2 Faculty of Computing, Engineering and Technology Asia Pacific University (APU) Kuala Lumpur, Malaysia
[email protected]
Sheroz Khan4 Faculty of Electrical and Computer Engineering International Islamic University Malaysia (IIUM) Kuala Lumpur, Malaysia
[email protected] The enormous and continuous growth in the wireless communication industry highly requires for developing several features such as light weight, low profile, single feed antennas and multiband. Among these unique features, multiband antennas are desirable such features allow us to integrating several RF modules for different frequencies into one antenna [2]. In contrast, the narrow bandwidth is the disadvantage and one of the most serious problems of microstrip patch antenna. There are many research works conducted these days with the aim of enhancing bandwidth using different methods [3]. Choosing the appropriate substrate is an important step for designing an antenna. In general, the permittivity of substrate considers as a fundamental material in the antenna design that controls many designing parameters such as bandwidth, efficiency, and radiation pattern [4]. The substrate in microstrip antennas is principally needed for the mechanical support of the antenna metallization [5]. The substrate of the antenna needs to have a dielectric material, for providing support for antenna metallization. The substrate with low dielectric constant performs well and produces better results than the high dielectric substrate [6]. As per the substrate analysis, T-Duroid 6002 is being used in the most of the designs, as it gives a better performance comparing to FR4 [7]. There are different feeding techniques, which are available to feed the signals into the microstrip patch antenna to maintain proper impedance matching and reducing signal loss in the antenna zone. These feeding techniques are divided into two groups such as connecting and non-connecting. For the connecting type, microstrip line is connected directly to the patch whereas an electromagnetic field coupling is placed between microstrip line and radiating patch in order to transfer the power in the non-connecting scheme [8]. The function of the feeding technique is very much significant in order to improve the input impedance matching that of the antenna, particularly efficiency based antennas.
2017 IEEE 15th Student Conference on Research and Development (SCOReD) On the efficiency and bandwidth based antenna designs, using different sized slots in the antenna region will improve the performance of the antenna system. There are different designs of microstrip patch antenna with ring slots are proposed for different wireless applications [9]. A simple structure antenna with two rings and slots on the radiation patch is implemented in one of the designs [10]. Another design of antenna, it is proposed a U-slot microstrip patch antenna loaded with metamaterial substrate for improving gain and efficiency [11]. The metamaterial substrate consists of an array of 5×6 split ring resonators. The resonators support to gain maximum power during the real time deployments. From the simulation results, it has been noted that the antenna with metamaterial achieves the low return losses. On the other hand, it is proposed a microstrip patch antenna with the usage of defected ground structure [12] for wireless communication. The designed antenna has an annular ring etched on the patch. Here, the rig slot has made on the radiation patch with a circular slot integrated on the ground plate in this design. The ring slot is used to obtain a good bandwidth and also to get a multiband operation frequency.
W=
429
3 × 108 2 × 3.4 × 109
2 2.94 + 1
W = 31.43 mm
(2)
(3)
The effective Dielectric constant (εreff) is calculated as follows:
ε reff =
εr + 1 + 2
εr − 1
ε reff =
2.94 + 1 + 2
3 .5 2 × 1 + 12 × 31 .43 2.94 − 1 3 .5 2 × 1 + 12 × 31.43
ε reff = 2.6 .
(4)
(5)
(6)
The objective of this work is to design and simulate a compact multi-band slot-ring microstrip patch antenna that covers 3.2 GHz for WiMAX 3.6 for mobile broadband (MBB) and 4.82 to 5.13 for WALAN (802.11a/h/j/n/ac). The antenna combines a patch structure with a slot and has an overall size of 45.25 X 50.43 mm.
The next calculation part is to determine the extension of length for the microstrip antenna. This calculation is very important to obtain the desired gain and bandwidth. It is further used for calculating resonant frequency of the antenna.
Following with this section of introduction, the antenna configuration as well as the details of geometrical structure are highlighted in the section II. Section III discusses the performance of the designed antenna in terms of simulated results and its relative antenna parameters. Finally, conclusions are presented in section IV.
W ε reff + 0.3 × h + 0.264 ΔL = 0.412h × w ε reff − 0.258 × h + 0.8
II. ANTENNA CONFIGURATION AND LAYOUT The standards of wireless devices are becoming smaller and smaller due to the technological advancements. In contrast, the user demands are increased high in these recent days. Hence, the appropriate design of antenna becomes more critical, detailed and more complex. Therefore, it is a vital to have detailed understanding of antenna design by the designers for effective performance. The structure and its dimensional calculations is a part of antenna design. The structure of the dimensions of the proposed microstrip patch antenna operated in multi-bands is illustrated in Fig. 1. The antenna is designed on a RT-Duroid 6002 substrate having a dielectric constant of 2.94 with loss tangent of 0.0012. The thickness of the substrate is 3.5 mm. The size of the ground plane is 44.25 × 52.43 mm and a 50Ω coaxial line is used to feed the antenna. The antenna geometry and its dimensions are calculated through the antenna design formulas from the antenna theory [13]. The basic formulae for length and width are given as follows: The width (W) of antenna can be expressed as
c W= 2 f0
2 εr + 1
(1)
The extension of length (∆L) is calculated as follows:
(
)
(
)
31.43 (2.6 + 0.3) × 3.5 + 0.264 ΔL = 0.412h × 31.43 (2.6 − 0.258) × 3.5 + 0.8 ∆L = 1.69.
(7)
(8)
(9)
Finally, the calculation of Length (L) and Effective Length (Leff) as follows:
Leff =
Leff =
c 2 × f r × ε reff 3 × 108 2 × 3.4 × 109 × 2.6
Leff = 27.36 × 10−3 Then, the length of the antenna is L = Leff − 2ΔL
(10)
(11) (12) (13)
L = 27.36 × 10−3 − 2 × 1.69
(14)
L = 24.25 mm.
(15)
2017 IEEE 15th Student Conference on Research and Development (SCOReD) The resultant radiated patch antenna size through the fundamental theory is 31.43 × 24.25 mm and it is slightly offcentered to improve the antenna performance by calibrating selected frequencies as a required resonator frequencies of operation. In addition, there are two rings are fixed at the corners in the designed patch antenna area. These rings help to generate the higher frequencies. Similarly, two semicircle slots are placed at the other two corners in the antenna area to improve the return loss and bandwidth of the antenna. The complete designed microstrip patch antenna design and its blue print is shown in the Fig. 1, mentioned with relevant dimensions. The Following parameters of the proposed antenna have taken for the purpose of simulation, which are shown in table 1 as given below: TABLE I.
ANTENNA DESIGN PARAMETERS Parameters
Symbol
Resonant Frequency Length
fr L
Calculated Value 3.4 GHz 24.25 mm
Width
W
31.43 mm
Thickness of a substrate
h
3.5mm
Relative dielectric constant
εr
2.94
Ground length
Lg
45.25 mm
Ground width
Wg
52.43 mm
Xf, Yf
(-2.89, 0)
Feeding location Impedance matching
Z
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major part, which is responsible for desirable antenna performance. The following simulation studies help us to explore the antenna parameters before moving further into the fabrication. The main goal of this antenna is to achieve a good bandwidth to cover the frequency band of three technologies as mentioned in the introduction. The antenna is designed and simulated by using HFSS, the High Frequency Structural Simulator. The multiple frequency band operation of designed antenna is studied to investigate the performance in terms of simulated reflection coefficient, impedance matching, bandwidth, radiation pattern, efficiency and gain. Fig. 2 represents the simulated reflection coefficient response. It can be seen from the graph, the antenna performance is good at the desired frequencies and exhibits good impedance matching of more than -10dB at all these frequencies. The antenna covers -10 dB impedance bandwidth of 90 MHz (3.18-3.27 GHz) at 3.2 GHz WiMAX technology, 80 MHz (3.55-3.63 GHz) at 3.6 GHz Wi-Fi frequency and 470 MHz (4.75-5.22 GHz) at the center frequency of 4.82 GHz and 5.13GHz.
48.46
Fig. 2. Simulated reflection coefficient response of the proposed antenna.
Fig. 1. Geometry of microstrip patch antenna.
III. AENTENNA TESTING AND ANALYSIS To validate the proposed compact size antenna as well as antenna structure optimization, significant parametric analysis is performed using simulated S-parameters. The simulation has been carried out with the assumption of null edge effects. The desired antenna parameters can be achieved closely by adjusting s-parameters of the antenna by modifying the structure and its dimensions. Hence the antenna geometry is a
Fig. 3. Simulated VSWR measurement of proposed antenna.
Another vital measurement of antenna parameter is VSWR (Voltage Standing Wave Ratio). VSWR is a transmission line parameter with respect to the antenna. The value of VSWR indicates that how well the antenna matched with the feed line wither in transmission or receiver mode.
2017 IEEE 15th Student Conference on Research and Development (SCOReD)
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It is also defined the ratio of output to input voltage. In a practical usage, its value was standardized as less than 2 for good impedance matching. Fig. 3 illustrates the simulated VSWR of the designed antenna and it is observed that it corresponding VSWR value is less than 2 at all the frequencies, which implies that exhibits good impedance matching and minimum signal loss.
Fig. 4. Simulated 2-D radiation patterns for the proposed antenna at 3.2 GHz.
Fig. 7. Simulated 2-D radiation patterns for the proposed antenna at 5.16 GHz.
Fig. 5. Simulated 2-D radiation patterns for the proposed antenna at 3.6 GHz.
Fig. 8. Simulated 3D polar Gain for the proposed antenna at 3.2 GHz.
Fig. 6. Simulated 2-D radiation patterns for the proposed antenna at 4.85 GHz.
Fig. 9. Simulated 3D polar Gain for the proposed antenna at 3.6 GHz.
2017 IEEE 15th Student Conference on Research and Development (SCOReD) The radiation pattern of the designed microwave patch antenna is simulated with different frequencies are plotted in Fig. 4-7. A far field radiation pattern for different frequencies are most significant matter in the antenna design because it provides clear understanding of field distribution and coverage direction. There are four different desired center frequencies are selected such as 3.2, 3.6, 4.85, and 5.16 GHz and its corresponding radiation patterns are simulated. From the graphical plots shown in Fig. 4-7, it is observed that the field pattern for all four center frequencies are mostly end fire field distribution pattern. While investigating the characteristics of extracted far field radiation patterns, the radiation pattern for 3.2 GHz produces perfect end fire pattern as compared with all other three patterns. Remaining three patterns also produces end fire pattern with some dips and peaks inside the field vicinity. Hence this simulated antenna can work well with 2G and 3G long range wireless communication applications.
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purpose. Fig. 12 represents the results of the simulated gain with respect to the frequency in gigahertz range of scaling. It is observed that attained maximum gain of 4.63dB, 3.45dB, and 7.15dB for the center frequencies at 3.2, 3.6, and 4.82 GHz respectively. Among this, the plot indicated that the antenna has a maximum gain value at 4.82 GHz. However, on more gain of -6.13dB at 5.13 GHz is also observed, which is a minimum gain produced by the designed antenna. These values shows that the antenna gain attained is sufficient to receive and transmit signals for the wireless applications.
Fig. 12. Simulated Gain in dB versus frequency in GHz.
IV. CONCLUSION
Fig. 10. Simulated 3D polar Gain for the proposed antenna at 4.82 GHz.
Fig. 11. Simulated 3D polar Gain for the proposed antenna at 5.13 GHz.
Fig. 8-11 demonstrates the 3D polar plot of simulated far fields gain in dB for the four different resonance frequencies. As per the antenna specification, gain parameter is one of the most common measurements to realize the ability of the antenna for the effective transmission and reception. These values are plotted as a function of frequency for the validation
A low profile microstrip patch antenna featured with ring slot operated at multi-bands for wireless applications has been presented in this study. The developed antenna has a compact structure with microstrip patch and two rings for producing higher frequencies and semicircle slots at the edges to boost parameters such as return loss and bandwidth. It is designed on a RT-Duroid 6002 substrate having a dielectric constant of 2.94 with 0.0012 loss tangent. The substrate thickness of 3.5 mm is used for antenna design. The size of the ground plane is 44.25 × 52.43 mm connected with 50 Ω coaxial feeding. The radiation patch of 31.43 × 24.25 mm is used and it is slightly off-centered to improve the antenna performance by calibrating frequencies into the resonator mode. In addition, there are two rings are fixed at the corners in the designed patch antenna area. It is demonstrated the antenna performance through simulated results and proved the ability working at four different frequency bands. Moreover, it is achieved reasonable gain for the effective signal radiation and reception as well as meets the requirement of 2:1 VSWR. This antenna is particularly attractive as a portable and fixed communication devices. REFERENCES [1]
Huiqing Zhai, Zhihui Ma, Yu Han, A Compact Printed Antenna for Triple-Band WLAN/WiMAX Applications, IEEE Antennas and Wireless Propagation Letters, Vol. 12, pp. 65- 68, January 2013.
2017 IEEE 15th Student Conference on Research and Development (SCOReD) [2]
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