IJEEE, Vol. 1, Issue 3 (2014)
e-ISSN: 1694-2310 | p-ISSN: 1694-2426
DESIGN & PARAMETRIC STUDY OF RECTANGULAR SLOT MICROSTRIP PATCH ANTENNA FOR UWB APPLICATIONS 1 1
Arvind Yadav, 2Dr. Kuldip Pahwa
M.tech Student, Department of E.C.E, M.M.U. Mullana, Ambala, Haryana, India 2 Professor, Department of E.C.E, M.M.U Mullana, Ambala, Haryana, India 1
arvinnd0519@gmail.com,
Abstract- A Microstrip fed antenna which consists of a rectangular patch with rectangular shaped slot incorporated into patch is presented for ultra wide band application with enhanced bandwidth. The proposed antenna achieves an impedance bandwidth of 8.9GHz (2.3-11.2GHz) with VSWR< 2 for over the entire bandwidth. Good return loss and radiation pattern characteristics are obtained in the frequency band of interest. The proposed antenna is designed on low cost FR-4 substrate fed by a 50-Ω microstrip line. The simulation was performed in High Frequency Structure Simulator Software (HFSS). The antenna parameters such as resonant frequency, return loss, radiation pattern and VSWR are simulated and discussed in this paper. The several factors affecting the bandwidth of the microstrip antenna such as the thickness of the substrate, the dielectric constant of the substrate and the shape of the patch also studied in this paper. Index Terms — Enhanced Bandwidth, Ultra wideband (UWB)
2
kpahwa2002@gmail.com
electrically thick substrate, gap coupled patches, the use of various impedance matching and feeding techniques [9-10]. However, simultaneously bandwidth enhancement and size reduction are becoming major design considerations for practical applications of microstrip antennas as improvement of one of the characteristics, normally results in degradation of the other, researchers have encountered that there is generally a tradeoff between size of antenna and wideband characteristics of antenna. In recent years, many techniques have been reported to achieve wideband patch antenna for modern wireless communication devices [11]. II. ANTENNA STRUCTURE AND DESIGN The three essential parameters for the design of a rectangular microstrip patch antenna are: Frequency of operation (
f0 ): The
resonant frequency of the
antenna must be selected appropriately. The resonant frequency selected for design is 7.5 GHz.
VSWR, HFSS.
Dielectric constant of the substrate ( r ): The dielectric
I. INTRODUCTION The accelerating growth of ultra-wideband (UWB) technology calls for efficient communication devices. Antennas, as an important part of every communication system, are required to offer characteristics such as compact size, light weight, easy fabrication process, omni-directional radiation properties, and wide bandwidth to be worthy of being used in UWB systems[1]. The Federal Communication Commission (FCC) allocation the unlicensed use of band from 3.1 to 10.6 GHz widely known as UWB technology and opens it for commercial applications for short range indoor and outdoor wireless communication [2].The UWB antenna is an significant component of UWB communication system and has drawn growing attention [3-5]. It is well known fact that microstrip patch antennas offers many advantages such as low profile, light weight, ease of fabrication and compatibility with printed circuits. However, the serious problem of patch antennas is their narrow bandwidth. To overcome their inherent limitations of narrow impedance bandwidth many techniques have been proposed and investigated, for example, slotted patch antennas [6 - 8], microstrip patch antennas on
material selected for the design is FR4-epoxy which has a dielectric constant of 4.4. A substrate with a high dielectric constant reduces the dimensions of the antenna. Height of dielectric substrate (h): For the microstrip patch antenna it is essential that the antenna is not bulky. Hence, the height of the dielectric substrate is selected as 1.5mm. The design parameters that are assumed and evaluated are shown in Fig.1 as below:
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Fig. 1 Side View of Antenna
Step 1: Calculation of the Width (W): The width of the Microstrip patch antenna is given by [12] following equation: c W= (1) ε +1 2f 2 www.ijeee-apm.com
Substituting εr=4.4, c=3x108m/sec, fo= 7.5GHz gives: W=12mm
Table 1 Parameters of Rectangular Slot Patch Antenna
PARAMETERS
DIMENSIONS
Substrate Length Substrate breadth Substrate thickness Dielectric constant of substrate Tangent loss
21mm 18mm 1.5mm 4.4 0.02
Patch length
9mm
Step 3: Calculation of Effective Length ( Leff ): The effective
Patch breadth
12mm
length is given [12]as: c L = (3) 2f ε Substituting: fo=7.5GHz, c=3x108m/sec, εreff =3.7 gives: Leff =10.2mm Step 4: Calculation of the Length Extension (ΔL): Equation below gives the length extension [12] as:
Input resistance of the Patch (Rin)
50 Ω
Length of slot (L1) Width of slot (w1)
5mm 8mm
Step 2: Calculation of Effective Dielectric Constant (εreff): The following equation gives the effective dielectric constant as [12]: ε +1 ε −1 h + 1 + 12 (2) 2 2 W Substituting εr=4.4, W=12mm, h=1.5mm gives: εreff =3.7 ε
∆
=
= 0.412
(ε (ε
. ) .
)
.
(4)
.
Substituting the values, the length extension (ΔL) is obtained as: ΔL=.6mm Step 5: Calculation of Actual Length of Patch (L): The actual length of the antenna can be calculated [12] as: L = L − 2 × ∆L (5) Substituting Leff =10.2mm and ∆L=0.6mm the actual length come out to be: L=9mm III. PARAMETERS OF RECTANGULAR SLOT ANTENNA In this section parameters of a rectangular slot antenna has been discussed which is printed on a dielectric substrate of FR4 with relative permittivity (εr) of 4.4. The fig 2 shows the patch with finite ground plane. The length of ground plane Lg is determined using parametric analysis and its optimum value is found to be 7.5mm.
Top View
Bottom View
The length Lg has a very important role in controlling the coupling between ground plane and patch. This coupling causes to spread of the impedance bandwidth and hence must be accurately measured. The various parameters of the patch antenna which includes shape of the patch , dielectric used, length and width of the patch ,thickness of patch and length and width of the slot as shown in table 1. IV. RESULT AND DISCUSSION OF RECTANGULAR SLOT PATCH ANTENNA The return loss, VSWR and gain of the proposed antenna is shown in Fig 3 (a, b, c) respectively. The discussed design achieves the return loss of -17.67dB and the bandwidth of 8.9 GHz (2.3- 11.2GHz) and corresponding VSWR is < 2 for entire bandwidth range. Simulated results show that the proposed antenna could be a good candidate for UWB applications.
Fig 3(a) Return Loss
Fig 2 Dimension of Rectangular Slot Patch Antenna www.ijeee-apm.com
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substrate increases the bandwidth increases and as the thickness of the substrate decreases the bandwidth decreases.
Fig 3(b) VSWR
Fig 4(a) Effect of the Substrate Height on the Bandwidth of the Antenna
However, thick substrates tend to trap surface wave modes, especially if the dielectric constant of the substrate is high. In addition, longer coaxial probe feeds will experience high inductive feed effects. Finally, if the substrate is very thick, radiating modes higher than the fundamental will be excited [13]. All of these effects degrade the primary radiator, cause pattern distortion, and detune the input impedance of the microstrip antenna. (b) Effect of variation in dielectric constant on the bandwidth of the antenna Fig 3(c) 3- D Polar Plot
V. PARAMETRIC STUDY OF RECTANGULAR SLOT WIDEBAND MICROSTRIP ANTENNA (a)Effect of variation in substrate thickness on the bandwidth of the antenna Table 2 Comparison of Different Substrate Thicknesses SUBSTRATE THICKNESS (mm)
DIELECTRIC CONSTANT (Îľ r)
OPERATING BAND (GHz)
BANDWIDTH (GHz)
1.5
4.4
2.3-11.2
8.9
1.2
4.4
2.8-10.7
7.9
1.7
4.4
2.0-12.8
10.8
Fig 4(b) Effect of the Dielectric Constant on the Bandwidth of the Antenna
It is known that the easiest way to increase the bandwidth of a microstrip antenna is to print the antenna on a thicker substrate. Fig 4(a) and table 2 show that as the thickness of the International Journal of Electrical & Electronics Engineering
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Table 3 Comparison of Different Substrate Materials DIELECTRIC CONSTANT (ε r)
SUBSTRATE THICKNESS (mm)
OPERATING BAND (GHz)
BANDWIDTH (GHz)
4.4
1.5
2.3-11.2
8.9
3.8
1.5
2.2-11.6
9.4
4.8
1.5
2.4-10.5
8.1
As it can be analyzed from the fig 4(b) and table 3 which shows that as the dielectric constant decreases than bandwidth increases and as the dielectric constant increases than bandwidth decreases. However, this has detrimental effects on antenna size reduction since the resonant length of a microstrip antenna is shorter for higher substrate dielectric constant. In addition, this antenna can easily be used in other frequency bands with different substrate materials [13]. (c) Effect of variation in slot length and width on the bandwidth of the antenna
and when L1 and W1 is (6*9) then both bandwidth and return loss is decreases as compared with (5*8) slot length and width. V. CONCLUSION This paper has proposed a simple design of patch antenna having a UWB range for communication. In the design a slot is incorporated into the rectangular patch to expand its bandwidth and to reduce the size of antenna .The designed antenna is very simple in look and small in size . Simulation results show that the antenna has VSWR < 2 from 2.3- 11.2 GHz and bandwidth of antenna is 8.9GHz .The antenna parameters such as return loss, VSWR, impedance bandwidth, gain have been studied. Simulated results of antenna show that the proposed antenna could be a good candidate for UWB application. The effects of the substrate thickness, the dielectric constant of the substrate and variation in slot position on the bandwidth have been studied. It has been found that, in order to obtain a wideband microstrip patch antenna with good efficiency, a thick substrate with a very low dielectric constant should be used. It has also been shown that these antennas can easily be used in other frequency bands with different substrate materials. REFERENCES
Fig 4(c) Effect of The Variation in Slot Length And Width on The Bandwidth of The Antenna Table 4 Comparison f Different Slot Length and Width SLOT LENGTH & WIDTH (L 1 & W 1)
DIELECTRIC CONSTANT (ε r)
OPERATING BAND (GHz)
BANDWIDTH (GHz)
L1=5&W1=8
4.4
2.3-11.2
8.9
L 1 = 4& W 1 = 9
4.4
2.2-11.7
9.5
L 1 = 6 & W 1 =7
4.4
2.4-10.8
8.4
It can be seen from the fig (c) and table 4, which shows that the variation of slot length L1 and slot width W1 effect bandwidth and return loss of the antenna. When L1 and W1 is (4*9) then bandwidth is increases but return loss is very less www.ijeee-apm.com
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[10] K. Mandal, S. Sarkar, and P. P. Sarkar, Bandwidth enhancement of microstrip antennas by staggering effect, Microwave Opt. Technol.Lett., vol. 53, no. 10, pp. 2446–2447, 2011. [11] C.-K.Wu and K.-L. Wong, Broadband microstrip antenna with directly coupled and parasitic patches, Microwave Opt. Technol. Lett.,Vol.22, no. 5, pp. 348–349, 1999. [12] Constantine A. Balanis, Antenna teory analysis and design (John Wiley & Sons, Inc., Hoboken, New Jersey, 2005). [13] Sanchez-Hernandez, D., Robertson, I. D., “A survey of broadband microstrip patch antennas,” Microwave Journal, pp. 6082, Sept. 1996.
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