Research On Key Technologies Of Reconfigurable Antenna In Multi-Standard Wireless Communication

With the development of science and technology,there are more and more wireless communication standards and numerous wireless communication standards will coexist for a long time.Modern wireless communication systems are developing towards high integration,multi-band or multi-mode,high performance,multi-function,intelligent and so on.Because of its sole performance,the traditional fixed antenna cannot meet the requirements of diversified applications.Reconfigurable antenna can improve or eliminate the performance constraints of the fixed antenna by changing its electromagnetic characteristics to cope with the different application environment and system requirements.In view of the technical requirements and problems of reconfigurable antenna on frequency response and radiation characteristics in multi-standard wireless communication systems under complex application background,the key technologies of multi-band frequency reconfigurable antenna,frequency and pattern reconfigurable antenna and frequency-gain response's selectivity reconfigurable antenna are furtherly researched in this dissertation.Several design methods are proposed,and relevant theoretical analysis,electromagnetic simulation and experimental verification are performed.The main research works and innovations are summarized as follows:(1)In order to meet the technical requirements of multi-band multi-mode operation with a large frequency span and flexible frequency setting in multi-standard wireless communication and the problems faced,a topology and method to design the multi-band frequency independently tunable antenna with high frequency ratio is proposed.Firstly,to solve the problem that parasitic modes will occur between the operation bands in the the traditional rectangular stacked patch antenna,a novel U-shaped coupled patch structure is designed and this structure can effectively suppress the excitations of parasitic modes between the operation bands.Then,in order to solve the problems of difficult expansion of frequency band in traditional multi-frequency structure and poor frequency independently tuning performance,a design method of multi-band antenna based on U-shaped coupling patch and nested topology is proposed.This design method has the advantages that,the number of the operation bands can be easily increased,the layers of substrate can be effectively reduced compared to traditional stacked topology,and the input impedance at different operation bands can be relatively independently adjusted so as to achieve independently frequency tuning and well matching at all operation bands.Finally,based on the proposed method,a dual-band,a tri-band and a quadri-band antenna with each band independently tunable are designed and implemented.Measurement demonstrates that the tuning range of each band of the quadri-band antenna is all above 10%,and it has a high frequency ratio of 5:1 with low parasitic resonance and independent frequency tuning performance.It provides a promising and practical solution for the highly integrated multi-standard wireless communication system based on the 2G/3G/4G/WiFi/WiMax standards.The research results have been accepted by the journal Microwave and Optical Technology Letters.An application for China's patent has already been submitted.(2)In order to meet the diversified requirements for frequency and pattern reconfiguration in multi-standard wireless communication and the problems faced,a method by codesigning multi-type antenna modes to achieve pattern reconfiguration is proposed to guide the fast design of pattern reconfigurable antenna for specific requirements.This method is starting by investigating the operation mode and radiation characteristics of basic-type antenna,and then integrating two or more different types of antennas together to codesign the pattern reconfigurable antenna according to the structural similarity criteria.According to this method,firstly,based on the codesign of monopole mode and patch mode,a mechanical pattern reconfigurable antenna with dual-band operation is designed.Its radiation pattern can be reconfigured to be directional or omnidirectional at dual-band operation.Then,also based on the codesign of monopole mode and patch mode,a frequency reconfigurable,pattern diversity antenna is furtherly designed.It has three operation modes,i.e.an omnidirectional pattern mode at the lower frequency band,a unidirectional pattern mode at the higher frequency band,or both of them working simultaneously.Finally,based on the codesign of patch mode and half-mode slot mode,a frequency and pattern reconfigurable antenna is designed.The frequency of the antenna can be tuned continuously,and the pattern can be scanned at different frequencies with a wide scanning angle of ±78° at H-plane.What's more,it also can be switched to a backward radiation state.The above design examples have proved that the proposed design method can improve the design efficiency,break through the limitations of the existing technology,and achieve more differentiated and diversified reconfigurable patterns.The relevant research results have been published in the journals IEEE Antennas and Wireless Propagation Letters and Microwave and Optical Technology Letters.Some of the research results have been submitted to the journal IEEE Transaction on Antennas and Propagation.An application for China's patent has already been submitted.(3)In order to solve the interference problem between adjacent bands in multi-standard wireless communications,the concept to control and reconfigure the sideband selectivity of the frequency-gain response characteristic in antenna is proposed for the first time.Based on terminal loaded transmission line theory,by introducing the idea of filtering antenna to codesign the antenna and filter,a method to change the frequency of radiation gain null in gain response,so as to control the sideband selectivity of frequency-gain response characteristic of antenna is proposed.Based on this method,a novel substrate integrated waveguide slot filtering antenna structure is proposed.By changing the position of the slot,three filtering antennas with different performance are designed.The first design has a radiation gain null at lower sideband.The second design has a radiation gain null at the upper sideband and the third design has a radiation gain null at each sideband.Thus,the gain selectivity can be controlled.Furtherly,a filtering antenna with a reconfigurable radiation gain null is designed.Its gain null can be switched to be located at the upper or lower sideband.Thus,the reconfiguration on sideband selectivity of the antenna gain response is realized.This part extends the function and research scope of the reconfigurable antenna.The relevant research results have been published in the journal IEEE Antennas and Wireless Propagation Letters,and accepted by the journal International Journal of Antennas and Propagation.Some of the research results have been submitted to the journal IEEE Antennas and Wireless Propagation Letters.