Design of on-glass antennas for FM diversity systems (アンテナ・伝播)

概要

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The monopole type antennas such as the conventional λ/4 monopole, tuned monopole, roof-mounted micro-antenna and shark fin antenna have been widely used for FM radio reception in various types of vehicles. These antennas, however, suffer from lack of durability and undesirable appearance. To solve these problems on-glass antennas have been used in various vehicles. But these on-glass antennas generally exhibit relatively low signal reception performance due to their poor impedance matching and low antenna gain especially in urban environment where multi-path fading exists. Recently, to improve the receiving performance, some luxury vehicles employ diversity on-glass antenna systems that incorporate two separated antennas in the rear window. In this paper, we report on the channel capacity and diversity gain of the on-glass rear window antennas. Using the radiation pattern of each antenna and the transfer matrix, the correlation coefficient and channel capacity are obtained. Then we observe the variation of the channel capacity by examining three basic design structures that consist of two separated bent striplines. The results show that the distance between the feed positions are the major factor that affects on the channel capacity. In addition the polarization of the two antennas gets more important when the distance between the feeds is greater than a certain threshold value.
2009-07-01