Design and Analysis of Compact Antennas and Diversity Antenna for Wireless Communication

• Main Authors: Zih-Hao Lu, 盧子豪
• Other Authors: Ding-Bing Lin
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/41521658313880477229

碩士 === 國立臺北科技大學 === 電腦通訊與控制研究所 === 92 === In this thesis, we will discuss two topics about antennas. First, the slow wave effects will be used to design the compact antenna. The elementary structure of the compact antenna is that shorting and feeding positions are located respectively on both sides of the designed antenna. The slow wave effect will be introduced by etching applicable geometric figures on radiator of the antenna and the slow wave effect can be changed by adjusting the etching position. The measurement results show that the significant slow wave effect is introduced, if the etching geometric figure on the radiator of the antenna is placed at the position where has large the current density. Then more obvious slow wave effect introduces the lower relative resonant frequency. So the antenna size can be reduced significantly by the introduction of slow wave property. Also, modifying the width and height of antenna is alternative way to reduce the size of antenna. The other topic about antenna presented in this thesis will study two configurations of switched-beam diversity antennas for wireless communication. In the first configuration, two patch antennas separating form a two elements antenna array. The feeding phases of each antenna element can be changed from in-phase to out-of phase by switching the appropriate pin-diodes on-off status. Then the array factor of the patch antenna array can be changed from end-fire direction to broadside direction. In the second configuration, two thin conductors are put on both sides of one dipole antenna and the both distances between each thin conductor and the dipole antenna are set as . For each thin conductor, there is a break point on the middle, then mount a pin-diode on the break point. Because the length of two thin conductors are longer than the length of the dipole antenna, two thin conductors will be equivalent as inductive reflector or capacitive reflector by switching the pin-diode to on or off status respectively. Hence, the main beams of this configuration can be switched and almost have 180o difference. For the above mentioned two configurations, the experiments show the switched-beams have low correlation coefficients 0.0318 and 0.0837 respectively. Only one feeding port is needed to configure the switched-beam antennas and the small distance between the array elements is needed to provide enough low correlation for the proposed configurations. These above mentioned antenna configurations are suitable to design the practical wireless communication systems. This is major contributions in this thesis.