Study On Application Of Electromagnetic Bandgap And Defected Ground Structure For Microstrip Line

The mobile communications and personal communications have been rapidly grown with wide applications in recent years. The microwave circuit with compact and high performance is one of the critical technologies in next generation wireless communication system. EBG (electromagnetic band-gap), DGS (defected ground structure) and their applications in microwave and millimeter wave present a new path for the communication system towards high compactness, performance and reliability. At the same time, with the fast development of computers, finite-difference time-domain (FDTD) method is becoming a powerful tool of analyzing these electromagnetic problems. Based on the characteristics of EBG and DGS, several new type practicable compact stopband and passband filters are proposed and FDTD analysis of one Parallel EBG microstrip line is studied in this dissertation. The main research works have been completed and discussed as follows:In Chapter 2, the Photonic Crystals is introduced briefly, and the fabrication technology, theoretical research method and application of Photonic Crystals(electromagnetic band-gap) in optical and microwave field are reviewed.In Chapter 3, based on investigation of the EBG microstrip lines proposed in the papers published in domestic and international, five types of EBG microstrip lines are designed. They are: (a) One type of EBG microstrip line, with two different periodic rectangle structure etched on both edges of the conductor line, can obtain a flat and low-rippled passband, and wider stopband or narrower passband without cascade connection of different EBG structures, the -3dB bandwidth of stopband is 70% and the -3dB bandwidth of passband is 15% only. The bandwidth of stopband or passband can be changed according to requirement. There is no enclosure problem for this EBG microstrip line, (b) Two types of EBG microstrip lines, with periodic EBG structure etched on the conductor line and in the ground plane for one microstrip, can realize narrower passband or wider stopband without cascade connection of different EBG structures. The stopband is deeper, and the bandwidth of stopband or passband can be changed according to requirement. The -3dB bandwidth of passband is about 8% and the -3dB bandwidth of stopband is about 81 % for the better one. (c) Two types of EBG microstrip lines are formed by etching rectangle or trapezium on the edge of the conductor line periodically.