Research On UWB Antenna Based On Fractal Structure

With the development of modern communication technology,more and more wireless communication devices have joined the modern communication device systems,so higher and more diverse requirements are put on the communication quality of the system.As one of the key devices in the wireless communication systems,the effectiveness of the systems depends on the antenna.It is equivalent to a person's mouth and ears in a communication system,and plays the role of receiving and transmitting electromagnetic wave signals.After many years of development,various types of antennas have been developed and have formed a huge family.The fractal technology have been applied to the design of antennas in recent years.The space-filling property itself can effectively reduce the size of the antenna and achieve the goal of miniaturization of the antenna.Another self-similar characteristic is multi-frequency resonance,which provides ideas for showing UWB(Ultra-Wide Band)characteristics.Therefore,it has become a new method and has good application prospects that designing an UWB antenna based on a fractal structure.The main contents of this master's thesis are:(1)An UWB antenna based on laminated fractal ring was proposed.The fractal structure consists of three main rings of different sizes and a number of small rings stacked to connect the main ring.An operating bandwidth of 11.6 GHz,relative bandwidth of 147%,Contains UWB spectrum that stabilizes uniform radiation,with good performance and suitable for UWB band wireless communication system.The test results of sample are close to the simulation,which verifies the feasibility of antenna design.(2)The structure of the fractal loop antenna was optimized.Both of the above and this antenna have the same main ring but each main ring was surrounded by four small rings.Impedance bandwidth of the proposed antenna is 9.2 GHz and the relative bandwidth is 133%.The antenna has good radiation characteristics and the overall structure is more compact.The antenna was fabricated and very similar to the simulation results.(3)An antenna miniaturization solution was proposed-a miniaturized fractal UWB antenna with crescent shape.The third order crescent shape fractal structure was etched on the circular radiation structure.Maximum size of the antenna only was19.5×13×1.6 mm~3,operating bandwidth range 3-17.5 GHz and relative bandwidth of143%.It can omnidirectional radiation and easy to integrate with other circuits.The difference between the produced antenna and the simulation results is small,which indicates that the antenna design is reasonable.(4)In order to improve the anti-jamming ability and reduce the waste of spectrum,a novel UWB fractal antenna with high selectivity band-notch characteristic has been designed.The fractal structure is to etch the fourth-order crescent on the octagonal radiation structure.The shape of the gap is loaded with notch structures at three different locations at the same time.The antenna works in 1.2-10.8GHz,it can suppress the three narrow-band signals in the working frequency band,solves the problem that notch bands is too wide.