The Fractal And The PBG Theory Applied In MEMS Reconfigurable Antenna Design

This dissertation researches the domains of the fractal antenna design,the analysis and the optimum methods of PBG (Photonic Band Gap), the PBGstructures design and the design of the MEMS frequency reconfigurableantenna.In the design of antennas, the use of fractal geometries has been a subjectof much attention in recent years. Many fractal geometries have been used inantenna/antenna array design. In fact, compared with all possible fractalgeometries, these fractal geometries are quite finite. Fractal geometries cannotbe effectively generated yet nowadays. In this thesis, a systemic method offractal shape generation is presented to solve this problem. This method issystemic, convenient and effective. A large number of fractal geometries canbe easily generated. It makes it possible to find some new fractal geometrieswhich may improve the performance of a fractal system. The square isselected to be the original shape to produce fractal geometries. Eightydifferent fractal geometries are generated and the twelve kinds among themare chosen to make the fractal antennas. The generated geometries include thetraditional Euclidean shapes, some famous fractal shapes, and the fractalshapes which are never been researched. Many of these antennas exhibit minisize or/and multi-band characters. Another log periodic patch antenna isresearched to validate the theory of the log periodic structure.A step optimum configuration method for PBG/EBG design based onS-parameters is proposed to solve the problem of organizing an excellentperformance PBG structure by using any given cells. The SOC method alsoprovides a new approach to construct a distance compact PBG. The SOCmethod explains the relationship between the behavior of band gap and thedistances among the cells. Choose cells properly according to the SOC method,a distance compact PBG will be obtained. The PBG group theory combinedwith the SOC method is a useful analysis theory of PBG structures.The fractal RASS (Rectangular Archimedean Spiral Slots) PBG and theRIDSS (Rectangular Increasing Distance Spiral Slots) PBG structures arepresented. These two kinds of structures have the super mini size and theexcellent performance. The length of one cell is only about 1/8 wavelength.A two microelectromechanical systems (MEMS) switches controlledfrequency-reconfigurable antenna with rectangular increasing distance spiralslots (RIDSS) PBG is presented. The antenna can work at four states (in theband 32-36GHz) with the different configuration of the switches. The RIDSSPBG structure can restrain the leakiness of RF energy through the DC controlfeed lines of the switches.A two MEMS switches controlled 4-state frequency-reconfigurableantenna with RIDSS PBG structures has been demonstrated. The experimentalresults have proved that the antenna works at four different states, 34.11GHz,32.09GHz, 33.13GHz and 36.20GHz, by shifting the state of the switches.RIDSS PBG structures have been used under the DC control feed lines of theMEMS antenna system. And the experiments of the scale-up similar antennasindicate that the PBG structures restrain the RF signal leakiness effectively inthe designed band. Applying the PBG structures in RF MEMS can enhance theperformance of the system and reduce the cost more. Furthermore, as an easilymanufacturable structure, the RIDSS PBG is suitable for integration inMMICs or other RF systems.