Design and Realization of the Magnetic Antenna in MW and SW Bands Based on Genetic Algorithm
|School||Harbin Engineering University|
|Course||Navigation,Guidance and Control|
|Keywords||MW and SW Ferrite Antenna Genetic Algorithm Active Circuit Meander Line|
As the rapid development of the communication technology, the dimension of receiver is smaller and smaller. As one of the most important components in receiver system, however, the dimension of antennas has become one of the bottlenecks restricting the further miniaturization of systems. The communication in medium wave (MW) and shortwave (SW) bands is one of the primary communication manners in sea, and the navigation system of loran-C in the U.S.A. also works in MW and SW bands, so antenna miniaturization of MW and SW bands’receiver has become the hot focus on studying. This thesis mainly studies the technology of antenna miniaturization in shortwave and medium wave receiver and their realization. Two different types of antennas are researched and designed, and different analytical methods are used for designing the two different types of antennas. Antenna theory and genetic algorithm (GA) is adopted in the design of ferrite antenna, and the simulation technology of electromagnetism based on the finite integration method is used for designing the meander line antenna in MW and SW bands.Firstly, based on the ferrite antenna, circuit characteristics and radiation characteristics of ferrite antenna are researched, and the structure of ferrite antenna in MW and SW bands is optimized and designed with GA. As to different antenna configurations, different fitness functions are adopted. According to the characteristics of MW and SW bands’receiver, the equivalent effective height is adopted as the fitness function. The ferrite rod and winding of antenna are given by GA. The resonant circuit of ferrite antenna is also designed on the basis of optimization model. The shortcoming of antenna is that the antenna’s gain is small. According to the minimum noise design principles, the BJT is used for designing a low noise amplifier (LNA) to increase antenna’s power input, make its gain increase and reduce the noise effect of component, enhance the radiant signal quality. The LNA targets are simulated and designed by ADS software. The simulation result indicates that the LNA input and output is matched with 50 ohm, the gain is 28.7dB, noise factor is 1.164, the performance is good. The paper also gives an available design plan about the omni-direction ferrite antenna, and designs the key circuit-90 degrees phase shifter. It is carried out and testified by ADS simulation software.Finally, the meander line antenna working in shortwave and medium wave bands is designed by using the simulation software CST Microwave Studio which is based on the method of finite integration in the paper, because radiation efficiency of the ferrite antenna is very low. The larger antenna has two resonant points in the paper, the resonant frequency of the first resonance point is 13.5MHz, the bandwidth of antenna is 0.58MHz, horizontal omni-directional radiation, and the gain is-2.6dBi.