(A) study on the antenna miniaturization and magneto-dielectric material application

Abstract

In recent years, there are two important trends in the mobile communication systems. One is the downsizing of devices. As the demands of the small, compact wireless communication system, the methods of device’s miniaturization have been developed rapidly. Especially, because the antenna occupies widely space in communication systems, the antenna miniaturization for mobile wireless applications has recently drawn a lot of attention. Accordingly, many methods have been proposed for the size reduction of antennas: current path adjustment, the addition of matching circuit, use of dielectric or magnetic material. However, antenna miniaturization results in the degradation of bandwidth, gain, and impedance matching and so on because the characteristics of the antenna are seriously affected by its size. Therefore, when antennas are developed, the relationship between the antenna downsizing and performances has to be considered. Another trend is the realization of MIMO. Future wireless communication systems should be capable of accommodating higher data rates than the current systems owing to the advent of various multimedia services. Accordingly, one of the effective methods for improving reliability and increasing the channel capacity is the MIMO system. In the MIMO system, the isolation among them is very important because the isolation between antennas affects the performance. The coupling between antennas decreases their efficiencies as part of the power that would normally be radiated is captured by the other antenna. This coupling may also cause unwanted interferences between a transmitting radio system and receiving one operating at another frequency band. So, recently, many papers have discussed about the isolation improvement methods between elements inside the wireless communication systems such as the corrugated ground plane with slots, EBG structures, embedding of the decoupling network, and conjugating matching and so on. This thesis presents the anten...