| With the fast development of wireless communication, miniaturization has become the trend of communication systems for military and civil use. Antennas are crucial parts in the wireless communication systems. The size of antenna is limited by both the working wavelength and the size of communication equipments. It is difficult to miniaturize the antenna. Recently, the ultra-wide band antennas are popularly used in military and civil communication systems because UWB antennas have such advances as anti-interference, good sharing of frequency resources, high transmission speed, simple structure and low cost. More attentions are paid to the UWB antennas and their applications in military and civil use.Nowadays, with the development of frequency spectrum and the seamless coverage of power, people enjoy the convenience and comfort brought by the advance of communications technology. However, we also face the health threaten caused by EM radiations. Generally, specific absorption rate, or SAR, is used to measure the amount of human exposure to EM energy. In order to protect the user of EM equipments, SAR limits are regulated by the industry.The main contribution of this paper is listed as follows. First of all, the principle and related technologies of antenna, UWB antenna and time-domain antenna are summarized. Secondly, a miniaturized antenna is designed and optimized. The electric size of antenna is less than 0.45λ×0.45λ×0.15λ and it works in the frequency band of 0.7-1.2GHz. Last but not least, a simplified model is proposed to predict the SAR characteristics of antenna. The accuracy and efficiency of simplified model are validated by both data-card antenna and BAN antenna. |
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