21-02-2012, 11:42 AM
Design and analysis with low side lobes of Fractal Linear Array Antenna
Abstract
In this paper, the fractal concept is used in the linear array antenna design to obtain multiband operation and reduced size. MATLAB programming language version 7.0.1 is used to simulate the fractal linear array antenna and their radiation pattern. Fractal Cantor linear array antenna of array pattern of 101 has been designed at a frequency of 2700 MHz with uniform and non uniform amplitude distribution. The performance of this array has been simulated. It is found that it operates at frequencies 2700 MHz, 900 MHz, 300 MHz, and 100 MHz. Two proposed models of Cantor linear array antenna having array patterns of 11011 and 1010101 are presented with uniform and amplitude distribution. The performance of these arrays has been simulated. The resulting frequency behavior is found that it operates at frequencies 2700 MHz and 540 MHz for the first model (11011) and 2700 MHz and 386 MHz for the second model (1010101). The frequencies have been selected in the VHF and UHF bands have been used in many applications in communication systems such as global system mobile (GSM), wireless local area network (WLAN), worldwide interoperability for microwave access (WIMAX) …. etc.
Keywords: Fractals, fractal arrays, antenna array, antenna radiation Patterns, Multi-band antennas, low side lobe antennas.
1.INTRODUCTION
The increasing range of wireless telecommunication services and related applications is driving the attention to the design of multifrequency (multiservice) and small antennas. The telecom operators and equipment manufacturers can produce avariety of ommunication systems, like cellular communications, global positioning, satellite communications, and others.Each one of these systems operates at several frequency bands. To give service to the users, each system needs to have an antenna that has to work in the frequency band employed for the specific system. The tendency during last years had been to use one antenna for each system, but this solution is inefficient in terms of space usage, and it is very expensive. The variety of communication systems suggests that there is a need for multiband antennas. The use of fractal geometry is a new solution to the design of multiband antennas and arrays. Fractal was first defined by Benoit andelbrot [1] in 1975 as a way of classifying structures whose dimensions are not whole numbers. These geometries been used previously to characterize unique ccurrences in nature that were difficult to define with Euclidean geometries, including the length of coastlines, the density of clouds, and branching of trees. Fractals can model nature very well. They can be used to generate realistic landscapes or sunsets, wire-rames of mountains, rough terrain, ripples on lakes, coastline, sea floor topography, and plants. Fractals can be divided into many types, as shown in figure (1).
Fractal applications have appeared in many branches of engineering and science. One such area is fractal electrodynamics in which fractal geometry is combined with electromagnetics. An introduction to the subject of fractal electrodynamics may be found in the excellent review by Jaggard [2]. This paper focuses on the application of fractal geometric concepts for the analysis and design of fractal linear array antennas.
II. FRACTAL ANTENNA ARRAYS
Fast recursive algorithms for calculating the radiation patterns of fractal arrays have recently been developed in [3-5]. These algorithms are based on the fact that fractal arrays can be formed recursively through the repetitive application of a generating
array. A generating array is a small array at level one used to recursively construct larger arrays at higher levels (i.e.). In many cases the generating sub array has elements that are turned on and off in a certain pattern. A set formula for copying, scaling, and translating the generating array is then followed in order to produce a family of higher order arrays. The array factor for a fractal antenna array may be expressed in the general form [4-5]
where represents the array factor associated with the generating array. The GA parameter is a scaling or expansion factor that governs how large the array grows with each successive application of the generating array and is a level of iteration. The expression for the fractal array factor given in eq. (1) is simply the product of a scaled version of a generating sub array factor. Therefore, they may regard eq. (1) as representing a formal statement of the pattern P
(1)
multiplication theorem for fractal arrays. The analysis and design of fractal linear arrays will be considered in the following section.
Abstract
In this paper, the fractal concept is used in the linear array antenna design to obtain multiband operation and reduced size. MATLAB programming language version 7.0.1 is used to simulate the fractal linear array antenna and their radiation pattern. Fractal Cantor linear array antenna of array pattern of 101 has been designed at a frequency of 2700 MHz with uniform and non uniform amplitude distribution. The performance of this array has been simulated. It is found that it operates at frequencies 2700 MHz, 900 MHz, 300 MHz, and 100 MHz. Two proposed models of Cantor linear array antenna having array patterns of 11011 and 1010101 are presented with uniform and amplitude distribution. The performance of these arrays has been simulated. The resulting frequency behavior is found that it operates at frequencies 2700 MHz and 540 MHz for the first model (11011) and 2700 MHz and 386 MHz for the second model (1010101). The frequencies have been selected in the VHF and UHF bands have been used in many applications in communication systems such as global system mobile (GSM), wireless local area network (WLAN), worldwide interoperability for microwave access (WIMAX) …. etc.
Keywords: Fractals, fractal arrays, antenna array, antenna radiation Patterns, Multi-band antennas, low side lobe antennas.
1.INTRODUCTION
The increasing range of wireless telecommunication services and related applications is driving the attention to the design of multifrequency (multiservice) and small antennas. The telecom operators and equipment manufacturers can produce avariety of ommunication systems, like cellular communications, global positioning, satellite communications, and others.Each one of these systems operates at several frequency bands. To give service to the users, each system needs to have an antenna that has to work in the frequency band employed for the specific system. The tendency during last years had been to use one antenna for each system, but this solution is inefficient in terms of space usage, and it is very expensive. The variety of communication systems suggests that there is a need for multiband antennas. The use of fractal geometry is a new solution to the design of multiband antennas and arrays. Fractal was first defined by Benoit andelbrot [1] in 1975 as a way of classifying structures whose dimensions are not whole numbers. These geometries been used previously to characterize unique ccurrences in nature that were difficult to define with Euclidean geometries, including the length of coastlines, the density of clouds, and branching of trees. Fractals can model nature very well. They can be used to generate realistic landscapes or sunsets, wire-rames of mountains, rough terrain, ripples on lakes, coastline, sea floor topography, and plants. Fractals can be divided into many types, as shown in figure (1).
Fractal applications have appeared in many branches of engineering and science. One such area is fractal electrodynamics in which fractal geometry is combined with electromagnetics. An introduction to the subject of fractal electrodynamics may be found in the excellent review by Jaggard [2]. This paper focuses on the application of fractal geometric concepts for the analysis and design of fractal linear array antennas.
II. FRACTAL ANTENNA ARRAYS
Fast recursive algorithms for calculating the radiation patterns of fractal arrays have recently been developed in [3-5]. These algorithms are based on the fact that fractal arrays can be formed recursively through the repetitive application of a generating
array. A generating array is a small array at level one used to recursively construct larger arrays at higher levels (i.e.). In many cases the generating sub array has elements that are turned on and off in a certain pattern. A set formula for copying, scaling, and translating the generating array is then followed in order to produce a family of higher order arrays. The array factor for a fractal antenna array may be expressed in the general form [4-5]
where represents the array factor associated with the generating array. The GA parameter is a scaling or expansion factor that governs how large the array grows with each successive application of the generating array and is a level of iteration. The expression for the fractal array factor given in eq. (1) is simply the product of a scaled version of a generating sub array factor. Therefore, they may regard eq. (1) as representing a formal statement of the pattern P
(1)
multiplication theorem for fractal arrays. The analysis and design of fractal linear arrays will be considered in the following section.