I. INTRODUCTION
Development of wireless communication system is possible by the attractive and challenging features of the antennas. The microstrip patch antennas have some challenging characteristics to develop the wireless communication system. The microstrip patch antenna has demand in practical field due to their advantageous properties, such as small size, light weight, low profile, and easy to fabrication and can be used in any printed electronic circuits. With the strong features, they have some inherent demerit such as single operating frequency, narrow bandwidth, and low gain. To overcome the drawbacks, various techniques are reported. In [Reference Deshmukh and Ray1], a compact broadband slotted rectangular microstrip patch antenna is designed. A U-shaped slot is loaded on the patch and maximum percentage bandwidth of 24.6% is achieved. It is reported in [Reference Mandal and Sarkar2] that, 86.79% bandwidth with 4.1 dBi peak gain is achieved by introducing U-shaped patch with inverted U-shaped slot on the ground plane. The bandwidth of the microstrip patch antenna may be enhanced by introducing impedance matching technique, reported in [Reference Pues and Van De Capelle3]. The ultra wide band (UWB) is obtained by the monopole concept in [Reference Oraizi and Hedayati4]. It is reported by Mondal and Sarkar that the bandwidth of the microstrip patch antenna is enhanced by introducing M-shaped radiating patch with U-shaped slot on the ground plane [Reference Mondal and Sarkar5]. In [Reference Mondal and Sarkar6], broadband is achieved by embedded multiple number of slots on the patch and ground plane of the rectangular patch antenna. Various broadband microstrip patch antennas are reported in [Reference Tseng and Wan7–Reference Nasimuddin and Chen10]. In this work, four broadband with high-gain microstrip patch antennas have been designed. The design antenna consists of V- and W-shaped radiating patch with U-shaped slot on the ground plane. The designed antenna is simulated using MOM-based Ansoft designer software.
II. ANTENNA CONFIGURATION
Antenna-1 and -2 are designed by the W-shaped radiating patch placed on the top of the modified square and circular ground planes, respectively. Similarly antenna-3 and -4 have been designed by the V-shaped radiating patch placed on the top of the same modified ground planes simultaneously. The poly tetra fluoro ethylene (PTFE) substrate with coaxial probe feed is used to design all the antennas. The relative permittivity (ε r ), thickness (h), and loss tangent (tan δ) of the glass PTFE substrate are 2.4, 1.6 mm, and 0.00022, respectively [Reference Mandal and Sarkar2]. The necessary parameters and dimensions of the antennas are given in Table 1. All the designed antennas in compact form are presented in Fig. 1.
Fig. 1. Modified proposed microstrip patch antenna.
Table 1. Dimensions of all the antennas (all dimensions are in mm).
III. ANTENNA RESULTS AND DISCUSSIONS
The simulated and fabricated results of four antennas with different configurations are presented. The effects of different shapes of the radiating patches with same ground plane and different ground planes with same radiating patch are demonstrated. Mainly the antenna gain, bandwidth, and size of the antennas are investigated.
Development of patch by cutting slits in a regular patch, changes the normal surface current density. Consequently, the fringing field also changes as a result the radiation pattern, gain, or other parameters also changes.
A) Results of antenna-1 and antenna-2
The simulated and measured characteristics of reflection coefficient with frequency of antenna-1 and -2 are given in Fig. 3. The simulated and measured frequency bands of antenna-1 and -2 are 5.33 GHz (3.13–8.46 GHz), 5.34 GHz (3.16–8.50 GHz) and 5.52 GHz (3.08–8.6 GHz), 5.54 GHz (3.06–8.60 GHz), respectively. The conventional patch antenna is generally resonant at a single frequency and this frequency may be varied by the modification of the antenna. In both the cases of antenna-1 and -2 three resonant frequencies occurred. The second resonance frequency of the modified antennas is same as that of the conventional antenna. However, the second resonance frequency is generated due to the W- or V-shaped radiating patch and remaining two resonant frequencies are obtained for the coupling effect between U-shaped slots on the ground plane and W- or V-shaped radiating patch.
Fig. 2. Panels (a), (c), (e), and (g) are the photographs of ground plane of antenna-1, -2, -3, and -4. Panels (b), (d), (f), and (h) are the photographs of radiating patch of antenna-1, -2, -3, and -4.
Fig. 3. Reflection coefficient with frequency
In all these cases, resonant frequencies at 3.32, 6.72, and 8.18 GHz for antenna-1 and 3.38, 5.05, and 7.22 GHz for antenna-2 are found. The gain of the antenna is shown in Fig. 4.The peak gain of antenna-1 and -2, respectively, 3.7 dBi at 3.3 GHz (simulated), 3.5 dBi at 3.3 GHz (measured) and 3.6 dBi at 3.3 GHz (simulated), 3.6 dBi at 3 GHz (measured) are found. Therefore, the percentage of bandwidth and gain of both the antennas are almost same but size of the antenna-2 is reduced significantly from 804.6 to 529 mm2.
Fig. 4. Antenna gain with frequency
B) Results of antenna-3 and antenna-4
Antenna-3 and -4 is designed using V-shaped radiating patch. The radiating patch W-shaped is replaced by the V-shaped radiating patch. The simulated and measured results of reflection coefficient and gain are given in Figs 5 and 6, respectively. Antenna-3 offers frequency band of 6.64 GHz (3.26–9.90 GHz) (simulated) and 6.84 GHz (3.2–10.04 GHz) (measured) with three resonant frequencies at 3.81, 6.62, and 8.6 GHz.
Fig. 5. Reflection coefficient with frequency
Fig. 6. Antenna gain with frequency response
Similarly the proposed antenna-4 offers simulated and measured frequency band, respectively, 6.48 GHz (3.28–9.76 GHz) and 6.97 GHz (3.04–10.01 GHz). In the proposed antenna four resonant frequencies are found at 3.54, 4.82, 6.9, and 8.64 GHz. The third resonance frequency is obtained for the V-shaped radiating patch and remaining due to the coupled of slot and radiating patch. Results of some published work with proposed antenna are given in Table 2. The simulated and measured results of all the antennas are shown in Table 3. Here proposed Antenna – 4 offers the highest gain of 5.1 dBi with maximum 106.8% impedance bandwidth.
Table 2. Results of published work with proposed antenna.
Table 3. Simulated and measured results of all antennas.
The graphical representation of maximum percentage bandwidth with maximum peak gain of all the antennas is given in Fig. 7. It is found from the analysis that the shape and size of the patch and ground plane are responsible to enhance the bandwidth and antenna gain. The novelty of the research work is broad band and outstanding gain, which is obtained by the small-size microstrip patch antenna. Antenna-4 simulated and measured distribution of stable electric field with the angle θ and ϕ are presented in Fig. 8. The three-dimensional (3D) radiation patterns with surface current distributions of all the antennas at first resonant frequency are presented in Fig. 9. From Fig. 9 it is also found that the front radiation is much better compared with back radiation. Front-to-back power ratio of antenna-4 offered attractive results because of back radiation power is negligible compare with others antenna. Considering the power ratio of antenna-4, a good gain of 5.1 dBi is achieved.
Fig. 7. Percentage of bandwidth (BW) with antenna gain response
Fig. 8. Radiation pattern of the proposed antenna for ϕ = θ = 0°
Fig. 9. 3D radiation pattern with surface current distribution (a) antenna-1, (b) antenna-2, (c) antenna- 3, and (d) antenna-4.
IV. CONCLUSION
Four broadband high-gain microstrip patch antennas are designed. 106.8% (3.04–10.01 GHz) bandwidth with peak gain of 5.1 dBi is achieved. The proposed antenna covers the frequency bands: IEEE 802.11a (5.15–5.35 GHz), (5.725–5.875 GHz), (5.15–5.85 GHz) for WLAN, ISM band 5.8 GHz for (WiFi and Bluetooth), HIPERLAN2 (5.45–5.725 GHz), HiSWaNa (5.15–5.25 GHz), C-band (4–8 GHz), and X-band (8–12 GHz). The designed antenna is of planar structure. Such type of broadband and good gain patch antenna may be applicable in modern wireless communication where simple geometrical structure and small size is preferred.
ACKNOWLEDGEMENTS
We acknowledge gratefully for measurement facilities provided by JU (Jadavpur University), India and Kalyani University, India.
Kalyan Mondal received the B.Tech. and M.E. degrees in Electronics and Communication Engineering from Kalyani Govt. Engineering College, West Bengal, India in 2008 and Indian Institute of Engineering Science and Technology (IIEST), Shibpur former BESUS, Howrah, India in 2011, respectively. His research interests are microstrip patch antenna and frequency-selective surface (FSS). He has contributed more than 26 research articles in different journals and conferences. He is currently working toward the Ph.D. degree at Kalyani University.
Partha Pratim Sarkar obtained his Ph.D. degree in Engineering from Jadavpur University in 2002. He has obtained his M.E. degree from Jadavpur University in 1994. He obtained his B.E. degree in Electronics and Telecommunication Engineering from Bengal Engineering College (Presently known as IIEST, Shibpur) in 1991. He is presently working as a Professor at the Department of Engineering and Technological Studies, the University of Kalyani. His area of research includes microstrip antenna, microstrip filter, frequency-selective surfaces, and artificial neural network. He has contributed to numerous (more than 250 publications) research articles in various journals and conferences of repute. He is a Life Fellow of IETE and IE (India).
