Design and Analysis of Inverted F-shaped Slotted Patch Multiband Microstrip Antenna for S, C, X,
and Ku Band Applications
Sifat Hossain Department of Electronics and
Communication Engineering Khulna University of Engineering &
Technology Khulna-9203, Bangladesh E-mail: [email protected]
Md. Sohel Rana Department of Electronics and
Communication Engineering Khulna University of Engineering &
Technology Khulna-9203, Bangladesh E-mail: [email protected]
Md. Mostafizur Rahman, SMIEEE Department of Electronics and
Communication Engineering Khulna University of Engineering &
Technology Khulna-9203, Bangladesh E-mail: [email protected]
Abstract— This paper looks into a brand-new multiband microstrip antenna design. The designed antenna can operate at 8 different frequencies between 2.5 GHz and 14.0 GHz. An inverted F-shaped slot is added to the radiating patch to create multi-band frequencies. Initially different patch sizes, substrate material, and different shaped slots are investigated for creating multiband and also improving antenna performance. An FR4 dielectric substrate is used whose relative permittivity is 4.4 and thermal conductivity is 0.3[W/K/m]. A microstrip line is also used for feeding. The resonant frequencies of 8 bands are 2.9 GHz, 5.05 GHz, 5.8 GHz, 8.5 GHz, 9.5 GHz, 10.9 GHz, 12.8 GHz, and 13.5 GHz with the reflected power of -16.3 dB, -14.9 dB, - 16.7 dB, -14.6 dB, -10.9 dB, -18.6 dB, -11.1 dB, and -20.9 dB respectively. The acquired bandwidth is satisfactory and the VSWR is improved, being less than 2. This antenna is designed for S, C, X, and Ku band applications so it can be used for many purposes. CST Studio Suite software is used to design all the simulation results.
Keywords—microstrip, multiband, patch, VSWR, slot, reflected power.
I. INTRODUCTION
Depending on different applications, antennas come in a variety of shapes. Overall, the microstrip patch antenna has a lot of interesting and appealing qualities. There doesn't appear to be any doubt that it will continue to have a wide range of applications. Low profile, light weight, compactness, conformability to a mounting structure, and simplicity of fabrication are a few of these qualities. These characteristics enable the practical use of microstrip antennas in a variety of commercial and as well as military applications, including radar and satellite communication, Wi-Fi, WIMAX, Bluetooth, and GPS applications [1].
Fig. 1. Constructional view of Microstrip Antenna
As usual, the microstrip antenna consists of ground on the bottom, a metallic patch on the top, and a dielectric substrate between the patch and ground as shown in Fig. 1.
Applying various types of slots on patches, using a low dielectric substrate, and increasing the substrate thickness are only a few of the effective and well-known ways to expand antenna bandwidth [2],[3]. As a result, multiband antennas are becoming more popular, particularly to reduce the number of antennas needed to combine several applications on a single antenna [4].
A multi-band microstrip patch antenna having a steady gain is proposed in [5]. It maintains a constant radiation pattern. The frequency ranges of 2.4 GHz-2.485 GHz, 3.3 GHz-3.7 GHz, 5.15 GHz-5.35 GHz, and 5.725 GHz-5.85 GHz are all simultaneously resonant for this microstrip antenna. [6]
presents a small multiband microstrip antenna. Inserting parasitic elements with inverted L and T shapes will enable multiband operation. In [7], the multiband frequencies are obtained via an additional split ring resonator. A small, multiband inverted F antenna is shown in [8]. The Wi-Fi and Wi-max frequency bands are covered by this multiband antenna. In the majority of the designs, cutting u-shaped slots [9], ground plane slots [10], inverted F-shape antennas [11]- [13], and defective ground planes [14]-[17] can be used to enable multiband functioning. The majority of antennas are made to operate in the 2 GHz-5 GHz frequency band for Wi- Fi, WIMAX, Bluetooth, and GPS applications [18]-[23].
However, there are some performance parameter restrictions on these reported antennas. The performance must therefore be optimized by future research.
In this research, the designed antenna operates at 8 different frequencies between 2.5 GHz and 14.0 GHz which also covers the S, C, X, and Ku band applications. The proposed construction consists of an inverted F-shaped slotted patch on the top side and ground at the lowest part. The source signal is supplied via the microstrip feeding line. For all resonant frequencies, the designed antenna can produce return losses of less than -10 dB. The gain and directivity are extremely good, and the VSWR is between 1 and 2.
The paper structure is divided into the following sections.
Design procedures of the designed antenna are described in Section II using several tactics, and results. Performance
analyses are included in Section III. Section IV provides the applications of the designed antenna. Finally, Section V offers some closing thoughts.
II. ANTENNA DESIGN AND SPECIFICATIONS
Realization of the applications to be completed and meeting the requirements of the parameters are the primary requirements for designing an antenna. Without a doubt, frequency is very much important. Calculating the physical dimensions comes next after settling on the necessary data. A software named CST Studio Suite is used to simulate and design the antenna. Initially, the layer of ground is planned.
This serves as the foundation for mounting the antenna. The substrate that is employed, which in turn depends on the value of relative permittivity, affects the antenna's thickness.
Therefore, it is necessary to calculate the substrate material's thickness. The substrate's second layer is attached to the ground layer. The last and most productive layer is a radiating patch of the antenna [24]. The easiest kind of feeding method is thought to be microstrip line feed. The conducting feed line often has a smaller size than the patch and delivers electricity through one of its ends. The flow chart illustrates the proposed antenna's step-by-step design processes in Fig .2.
Fig. 2. Flow chart of the designed Microstrip Slotted Patch Antenna.
Some equations are used for the proposed antenna design.
The required equations are given below:
𝑊 = "#$! $%&'(" (1)
L = 𝐿)## − 2 △ L
(2)
where, L = patch length 𝐿)## = effective length
△ L = extension of length
𝐿)## = "#$! $ℇ+,," (3) where ℇ)## = effective dielectric constant of substrate
𝑋# = $ℇ+,,- and 𝑌# = ." (4) where 𝑋# = input position in the X axis.
𝑌# = input location in the Y axis.
△ L = 0.412h ('+,,&$.1)(!"&".34) ℇ+,,('+,,5$."67)(!"&.7)
(5)
ℇ)## = (ℇ8&%)" + (ℇ85%)" [1 + 12:9]% "⁄ (6)
𝐿< = 6ℎ + L (7)
𝑊< = 6ℎ + W (8)
The parametric dimensions are calculated by using the following equations for creating an antenna with better performance. Table I shows the parametric dimensions.
TABLE I. SPECIFICATIONS OF THE DESIGNED ANTENNA
Parameter Name Value (mm)
Ground Length (Lg) 20.233
Ground Width (Wg) 16.524
Substrate Length (Ls) 20.233 Width of substrate (Ws) 16.524
Patch Length (Lp) 11.861
Width of patch (Wp) 16.632
Ground Thickness (Tg) 0.0289 Substrate Thickness (Tsub) 1.7531 Thickness of Patch (Tp) 0.0289
Fig. 3. 3D image of proposed Microstrip Slotted Patch Antenna.
In Fig. 3, the proposed antenna is made of a metallic patch on the upper side which is an inverted F shaped slotted, a ground on the lower side, and a substrate in the between of patch and ground. The ground and patch of the designed antenna are made of copper annealed (lossy). The substrate is made of FR4, which is a dielectric material. This material's relative permittivity is 4.4 and thermal conductivity is 0.3[W/K/m]. To get a targeted resonant frequency and better value of return loss, VSWR, directivity, gain, and bandwidth of the designed antenna, the geometric parameters are changed. Different-shaped slotting is applied to the patch for creating a multiband.
III. SIMULATION RESULTS ANALYSIS AND DISCUSSION The proposed antenna is designed and simulation results are examined by using CST Studio Suite software. In order to demonstrate how different parameters affect the frequency, parametric analysis is carried out. It has been found that increasing the patch length causes the resonant frequency to begin to fall while decreasing the patch length causes the frequency to begin to climb. The resonant frequencies shift consistently as the patch size changes. The required operating frequency is reached at 2.9 GHz, 5.05 GHz, 5.8 GHz, 8.5 GHz, 9.5 GHz, 10.9 GHz, 12.8 GHz, and 13.5 GHz, respectively, after optimizing the patch length along with other parameters.
Fig. 4. S-Parameters of proposed Microstrip Patch Antenna.
S11 is the parameter that is most frequently used and quoted in relation to antennas. The reflection coefficient, also known as return loss (S11), is the measurement of reflected power from the antenna. No power is radiated if S11=0 dB which means all power is reflected. When return loss or S- parameter is less than -10dB, 90% of the available power must be transmitted to the antenna. The 8 bands of the designed antenna are below -10 dB which is shown in Fig. 4. The resonating frequencies of these bands are 2.9 GHz, 5.05 GHz, 5.8 GHz, 8.5 GHz, 9.5 GHz, 10.9 GHz, 12.8 GHz, and 13.5 GHz with the return loss of -16.3 dB, -14.9 dB, -16.7 dB, - 14.6 dB, -10.9 dB, -18.6 dB, -11.1 dB, and -20.9 dB respectively.
The bandwidth for each band of the designed antenna is shown in Fig. 5.
Fig. 5. Bandwidth of designed Microstrip Antenna.
The bandwidths of the designed antenna are 127.7 MHz, 101.5 MHz, 175.3 MHz, 211.3 MHz, 190.5 MHz, 447.1 MHz, 270.5 MHz, and 625.9 MHz respectively.
It is crucial to achieve VSWR between 1 and 2 virtually in order to avoid the mismatch between the feed line and an antenna [25].
For the profound frequencies, the VSWR of 1.4, 1.4, 1.3, 1.5, 1.8, 1.3, 1.8, and 1.2 are obtained, as shown in Fig. 6.
Fig. 6. VSWR of designed Microstrip Patch Antenna.
In electromagnetics, an antenna's directivity is a quantity that determines how much of the radiation it emits and is focused in a single direction. It is the ratio of an antenna's radiation intensity in one direction to its overall average radiation intensity. By a radiation efficiency factor, an antenna's directivity is greater than its gain. Since many antennas are made to transmit electromagnetic waves over a restricted angle or in a single direction, directivity is a crucial measurement. An actual antenna's directivity can range from 1.76 dBi to 50 dBi for short dipole and large dish antennae respectively.
Fig. 7. Directivity of designed Microstrip Antenna.
The values of directivity of the designed antenna are 5.03 dB, 4.91 dB, 6.02 dB, 8.67 dB, 7.89 dB,6.57 dB, 7.27 dB, 6.74 dB as shown in Fig. 7.
The far-field region, also known as the Fraunhofer region, is the area that is most remote from the antenna and is dominated by electromagnetic fields that are radiated from it.
The radiative near-field region is immediately adjacent to this zone. An antenna's radiation pattern in this area is unaffected by its distance from the source.
Fig. 8. Far-field directivity of the designed antenna at Phi=0.
Fig. 9. Far-field directivity of the designed antenna at Phi=90.
Fig. 10. Far-field directivity of the designed antenna at Theta=90.
Far-field directivity of the designed antenna at Phi=0, Phi=90, and Theta=90 is shown in Fig. 8, Fig. 9, and Fig. 10 respectively.
The antenna gain, which combines the radiation efficiency and directivity of the antenna, is a crucial performance measure in electromagnetics. The gain in a transmitting antenna refers to how successfully the antenna transforms input power into radio waves traveling in a particular direction. The receiving antenna gain indicates how effectively it changes radio waves that are coming from a specific channel into electrical power. Gain is taken to mean the gain at its maximum or the gain of the antenna's primary lobe direction when the direction is not indicated. The antenna pattern, also known as the radiation pattern, is a representation of the gain where it is a function of direction.
Fig. 11. Gain of the proposed Microstrip Antenna.
The gain of each band of the antenna is shown in Fig. 11.
The values of the gain are 2.3 dB, 0.4 dB, 1.9 dB, 3.9 dB, 2.7 dB, 0.5 dB, 1.3 dB, and 1.2 dB.
Fig. 12. Far-field gain of the designed antenna at Phi=0.
Fig. 13. Far-field gain of the designed antenna at Phi=90.
Fig. 14. Far-field gain of the designed antenna at Theta=90.
In Fig. 12, Fig. 13, and Fig. 14, far-field gain at Phi=0, Phi=90, and Theta=90 are shown respectively.
The antenna is designed is to create a multi-band and from the simulation result, it is clear that it can be applied for many applications because its resonant frequency is located at S, C, X, and Ku bands. The target of this study is to design a multi- band antenna for many different types of applications with greater performance. A comparison with previous research is given in Table II.
TABLE II. COMPARISON WITH PREVIOUS WORK
Reference Analyzed Parameter
[25] Return loss= -19.9737 dB, -22.7307 dB and -21.9667 dB VSWR= 1.7483, 1.2709 and 1.3881 Directivity= 0.57 dB, 0.15 dB, 0.43 dB, 4.14 dB, 6.53 dB, 1.21 dB, 2.26 dB.
Gain= 4.435 dB, 3.6602 dB and 5.6402 dB (Covers 3 bands)
[26] VSWR= 1.25, 1.44, 1.19, 1.24, 1.05, 1.45, 1.11
Directivity= 0.57 dB, 0.15 dB, 0.43 dB, 4.14 dB, 6.53 dB, 1.21 dB, 2.26 dB
Gain= 4.49 dB, 0.44 dB, 0.37 dB, 3.26 dB, 6.76 dB, 1.36 dB, 2.91 dB (covers 7 bands)
[27] Return loss= -11.15 dB, -17.07 dB, -13.57 dB Bandwidth= 34 MHz, 176 MHz, 307 MHz Gain= 1.34 dB, 3.81 dB, 4.91 dB
Directivity= 1.64 dB, 3.88 dB, 5.07 dB (covers 3 bands)
[28] Return loss= -19.6 dB, -14.8 dB, -10.3 dB, -29.5 dB, -11.1 dB, -12.7 dB, -11.6 dB, -14 dB, -10.1 dB, -13.6 dB, and -11 dB VSWR= 1.4, 1.2, 1.7, 1.9, 1.1, 1.5, 1.8, 1.5, 1.6, 1.8 and 1.9 Bandwidth= 70 MHz, 60 MHz, 40 MHz, 90 MHz, 80
MHz, 40 MHz, 80 MHz, 10 MHz, 60 MHz and 10 MHz.
Gain= 4.5 dBi, 2 dBi, 1.4 dBi, 1.4 dBi, 2.7 dBi, 0.3 dBi, 2.4 dBi, 2.4 dBi, 2 dBi, 9.5 dBi, and 1.7 dBi Directivity= 2.7dB, 2.5 dB, 3.4 dB, 3.6 dB, 4 dB, 4 dB,
2.4 dB, 4.8 dB, 5.3 dB, 5.6 dB and 5.34 dB.
(covers 11 bands) Proposed
Work
Return loss= -16.3 dB, -14.9 dB, -16.7 dB, -14.6 dB, - 10.9 dB, -18.6 dB, -11.1 dB, and -20.9 dB VSWR= 1.4, 1.4, 1.3, 1.5, 1.8, 1.3, 1.8, and 1.2 BW= 127.7 MHz, 101.5 MHz, 175.3 MHz, 211.3 MHz, 190.5 MHz, 447.1 MHz, 270.5 MHz, and 625.9 MHz Gain= 2.3 dB, 0.4 dB, 1.9 dB, 3.9 dB, 2.7 dB, 0.5 dB, 1.3 dB, and 1.2 dB
Directivity= 5.03 dB, 4.91 dB, 6.02 dB, 8.67 dB, 7.89 dB,6.57 dB, 7.27 dB, 6.74 dB
(covers 8 bands and works for S, C, X and Ku band)
This comparative table demonstrates how much better the proposed antenna performs. The designed antenna matches the transmission line for the best VSWR values and has very little reflected power. The designed antenna's bandwidth, gain, and directivity characteristics are key factors in increasing effectiveness and performance. This antenna is ideal for S band, C band, X band, and Ku band applications, and this is the big advantage of this antenna that one antenna can be applied for many applications.
IV. APPLICATION
The proposed antenna covers the S, C, X, and Ku band applications with the operating frequencies of 2.9 GHz, 5.05 GHz, 5.8 GHz, 8.5 GHz, 9.5 GHz, 10.9 GHz, 12.8 GHz, and 13.5 GHz. An area of the microwave spectrum with frequencies ranging from 2 to 4 GHz is known as the "S-band"
according to the IEEE. Thus, at 3.0 GHz, it crosses the traditional line separating the UHF and SHF bands. The S- band is utilized by weather radar, ship radar, air traffic control, and some satellite communications. 5.05 GHz is used for WLAN and 5.8 GHz is frequently used in wireless audio and video systems, Wi-Fi, radio local area networks, WLAN applications, ISM applications, and WiMAX. In communication engineering, the X band's frequency range of roughly 7.0-11.2 GHz is relatively arbitrarily fixed. IEEE defines the frequency range for radar engineering as 8–12 GHz.
Radar and satellite, as well as wireless computer networks, use the X band. 13.5 GHz is the frequency of the Ku-band which is mainly used for satellite communications.
V. CONCLUSION
This research proposes a design for a multiband microstrip antenna that operates between 2.5 GHz and 14.0 GHz. An inverted F-shaped slot is applied to the patch for creating a multiband and also microstrip line is added for feeding.
Different parameter optimization is needed for getting better return loss, bandwidth, VSWR, gain, and directivity. All resonant frequencies have return losses that are less than -10 dB. The proposed antenna's simulation results show that it will perform better for the S, C, X, and Ku band applications. A comparison with previous research is shown and it is very clear that the designed antenna is much better than the others.
All of the aforementioned applications are compatible with the antenna due to its justified return loss, VSWR, and positive gain. Fabricating the antenna and testing the results would be the next steps. The antenna's limited gain and restricted bandwidth must be considered.
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