Metamaterial-inspired and Defected-ground Techniques for High Performance Baluns and Antennas.

摘要

Defected ground structures and metamaterial inspired transmission lines are two emerging techniques which have been recently used in high frequency component designs to overcome the limitations of traditional transmission lines. They can help to improve bandwidth, reduce size and enhance performance of high frequency components. This dissertation is a study of the use of these techniques in antenna and balun designs to reduce the size, to get wide bandwidth and to encourage high performance of these circuits. This study also addresses the challenges and trade-offs faced when applying these transmission line techniques.;In this dissertation, the metamaterial inspired transmission line is applied to design antennas for RF energy harvesting systems. Among them, a design and study of wideband planar vialess CRLH antenna is introduced. This antenna gets over 300 MHz bandwidth for the operating frequency around 900 MHz. For harvesting RF energy at multi-bands, a novel triple-band antenna design which radiates at 900 MHz, 1900 MHz and 2400 MHz frequency bands is presented. In addition, a new design method for high efficiency triple band rectifiers is also proposed for this multi-bands RF energy harvesting system.;A novel ultra wideband balun using defected ground structure transmission line is also incorporated into the design studied in this dissertation. The study of this design method will start with the 23:1 bandwidth ratio balun. Besides, the design of 2 to 1 impedance transformation balun is also proposed. This balun has high balanced ports isolation and can match well to 50 Ohm at all 3 ports.