11-12-2012, 02:09 PM
Triple Band Microstrip Patch Antenna With Defected Ground Plane
[attachment=43359]
Abstract
In this rapid changing world in wireless communication systems, multiband antenna has been playing a very important role for wireless service requirements. Wireless local area network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) have been widely applied in mobile devices such as handheld computers and intelligent phones. These two techniques have been widely considered as a cost-effective, viable, and high-speed data connectivity solution, enabling user mobility.
Introduction
In modern wireless communication systems, multiband antenna has been playing a very important role for wireless service requirements. Wireless local area network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) have been widely applied in mobile devices such as hand held computers and intelligent phones. These two techniques have been widely recognized as a viable, cost-effective, and high-speed data connectivity solution, enabling user mobility With the rapid development of the modern wireless communication system, antenna design has turned to focus on wide multiband and small simple structures that can be easy to fabricate. To adapt to the complicated and diverse WLAN and WiMAX environments.
Aim and Objective
The aim of my project is to design a microstrip patch antenna giving triple band performance using defected ground plane. In the last few years many people have proposed different types of microstrip antenna but this antenna is very compact comparing to other microstrip patch antenna.
Thesis outline
Chapter 2: This chapter presents the basic theory of MPAs, including the basic structures, feeding techniques and characteristics of the MPA. Then the advantages and disadvantages of the antenna are discussed and the methods of analysis used for the MPA design
Feed Techniques
There are different techniques available to feed or transmit electromagnetic energy to a microstrip antenna. The four most popular feeding methods are the Microstrip line, coaxial probe, aperture coupling and proximity coupling.
Coaxial Feed
The Coaxial feed or probe feed is a very common technique used for feeding Microstrip patch antennas. As seen from Figure 2.2, the inner conductor of the coaxial connector extends through the dielectric and is soldered to the radiating patch, while the outer conductor is connected to the ground plane.
Microstrip Feed line
In this type of feed technique, a conducting strip is connected directly to the edge of the Microstrip patch as shown in Figure 2.3. The conducting strip is smaller in width as compared to the patch and this kind of feed arrangement has the advantage that the feed can be etched on the same substrate to provide a planar structure The purpose of the inset cut in the patch is to match the impedance of the feed line to the patch without the need for any additional matching element. This is achieved by properly controlling the inset position. Hence this is an easy feeding scheme, since it provides ease of fabrication and simplicity in modeling as well as impedance matching. However as the thickness of the dielectric substrate being used, increases, surface waves and spurious feed radiation also increases, which hampers the bandwidth of the antenna [1]. The feed radiation also leads to undesired cross polarized radiation.
Aperture Coupled Feed
In this type of feed technique, the radiating patch and the Microstrip feed line are separated by the ground plane as shown in Figure 2.4. Coupling between the patch and the feed line is made through a slot or an aperture in the ground plane. The coupling aperture is usually centered under the patch, leading to lower cross polarization due to symmetry of the configuration. The amount of coupling from the feed line to the patch is determined by the shape, size and location of the aperture. Since the ground plane separates the patch and the feed line, spurious radiation is minimized. Generally, a high dielectric material is used for the bottom substrate and a thick, low dielectric constant material is used for the top substrate to optimize radiation from the patch [1]. The major disadvantage of this feed technique is that it is difficult to fabricate due to multiple layers, which also increases the antenna thickness. This feeding scheme also provides narrow bandwidth (up to 21%).
Proximity Coupled Feed
This type of feed technique is also called as the electromagnetic coupling scheme. As shown in Figure 2.5, two dielectric substrates are used such that the feed line is between the two substrates and the radiating patch is on top of the upper substrate. The main advantage of this feed technique is that it eliminates spurious feed radiation and provides very high bandwidth (as high as 13%), due to overall increase in the thickness of the microstrip patch antenna. This scheme also provides choices between two different dielectric media, one for the patch and one for the feed line to optimize the individual performances.
[attachment=43359]
Abstract
In this rapid changing world in wireless communication systems, multiband antenna has been playing a very important role for wireless service requirements. Wireless local area network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) have been widely applied in mobile devices such as handheld computers and intelligent phones. These two techniques have been widely considered as a cost-effective, viable, and high-speed data connectivity solution, enabling user mobility.
Introduction
In modern wireless communication systems, multiband antenna has been playing a very important role for wireless service requirements. Wireless local area network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX) have been widely applied in mobile devices such as hand held computers and intelligent phones. These two techniques have been widely recognized as a viable, cost-effective, and high-speed data connectivity solution, enabling user mobility With the rapid development of the modern wireless communication system, antenna design has turned to focus on wide multiband and small simple structures that can be easy to fabricate. To adapt to the complicated and diverse WLAN and WiMAX environments.
Aim and Objective
The aim of my project is to design a microstrip patch antenna giving triple band performance using defected ground plane. In the last few years many people have proposed different types of microstrip antenna but this antenna is very compact comparing to other microstrip patch antenna.
Thesis outline
Chapter 2: This chapter presents the basic theory of MPAs, including the basic structures, feeding techniques and characteristics of the MPA. Then the advantages and disadvantages of the antenna are discussed and the methods of analysis used for the MPA design
Feed Techniques
There are different techniques available to feed or transmit electromagnetic energy to a microstrip antenna. The four most popular feeding methods are the Microstrip line, coaxial probe, aperture coupling and proximity coupling.
Coaxial Feed
The Coaxial feed or probe feed is a very common technique used for feeding Microstrip patch antennas. As seen from Figure 2.2, the inner conductor of the coaxial connector extends through the dielectric and is soldered to the radiating patch, while the outer conductor is connected to the ground plane.
Microstrip Feed line
In this type of feed technique, a conducting strip is connected directly to the edge of the Microstrip patch as shown in Figure 2.3. The conducting strip is smaller in width as compared to the patch and this kind of feed arrangement has the advantage that the feed can be etched on the same substrate to provide a planar structure The purpose of the inset cut in the patch is to match the impedance of the feed line to the patch without the need for any additional matching element. This is achieved by properly controlling the inset position. Hence this is an easy feeding scheme, since it provides ease of fabrication and simplicity in modeling as well as impedance matching. However as the thickness of the dielectric substrate being used, increases, surface waves and spurious feed radiation also increases, which hampers the bandwidth of the antenna [1]. The feed radiation also leads to undesired cross polarized radiation.
Aperture Coupled Feed
In this type of feed technique, the radiating patch and the Microstrip feed line are separated by the ground plane as shown in Figure 2.4. Coupling between the patch and the feed line is made through a slot or an aperture in the ground plane. The coupling aperture is usually centered under the patch, leading to lower cross polarization due to symmetry of the configuration. The amount of coupling from the feed line to the patch is determined by the shape, size and location of the aperture. Since the ground plane separates the patch and the feed line, spurious radiation is minimized. Generally, a high dielectric material is used for the bottom substrate and a thick, low dielectric constant material is used for the top substrate to optimize radiation from the patch [1]. The major disadvantage of this feed technique is that it is difficult to fabricate due to multiple layers, which also increases the antenna thickness. This feeding scheme also provides narrow bandwidth (up to 21%).
Proximity Coupled Feed
This type of feed technique is also called as the electromagnetic coupling scheme. As shown in Figure 2.5, two dielectric substrates are used such that the feed line is between the two substrates and the radiating patch is on top of the upper substrate. The main advantage of this feed technique is that it eliminates spurious feed radiation and provides very high bandwidth (as high as 13%), due to overall increase in the thickness of the microstrip patch antenna. This scheme also provides choices between two different dielectric media, one for the patch and one for the feed line to optimize the individual performances.