【作者】 赵国研；

【导师】 李文兴；

【作者基本信息】 哈尔滨工程大学 ， 通信与信息系统， 2010， 硕士

【摘要】 一直以来,有关天线小型化与宽带化的新理论与新技术都是天线领域的研究热点。随着高性能电子器件的不断涌现,越来越多的新技术从理论走向了实践,天线的带宽也因此而做的越来越宽。但是为了有效地实现电磁能量的转换,在设计天线时需保持一定的天线尺寸。尤其在短波波段,天线的实际尺寸都较大,短波天线的小型化也就难以实现。有源天线由于易于实现天线的小型化,且能够有效地解决无源电小天线所存在的频带窄、效率低等问题,而越来越受到天线工作者的关注。有源天线相对于无源天线来说具有很多优点,如提高天线系统的增益、利于实现电路间的级联以及拓宽天线的工作带宽等。但同时由于引入了有源器件,有源电路部分在放大有用信号的同时也增强了无用噪声。因为有源器件是不可逆的,有源接收天线不可以直接用来做发射天线。在发射天线系统中,天线的辐射电阻是频率的敏感函数,天线电尺寸的减小使得天线的输入端阻抗随工作频率剧烈变化,严重的限制了有源发射天线的工作带宽与输出功率,从而不能实现有源发射天线的宽带化。本文针对有源发射天线因为带宽不够宽、功率容量受限而导致在短波波段不能得到广泛地应用等问题,研究新的解决方案。文中设计了一种新的负阻抗变换器,通过其阻抗变换作用来改善发射天线的输入阻抗特性,从而大大地拓宽了有源发射天线的带宽。仿真结果表明,该负阻抗变换器不仅能够有效地减小对天线电长度变化十分敏感的输入电抗的影响,还能够提高天线系统的输入电阻,使有源发射天线在短波波段内的输入阻抗不受频率变化的影响,较好地实现与50Ω同轴电缆匹配,进而解决了有源发射天线在短波波段的宽带化问题。更多还原

【Abstract】 So far, the new theories and new technologies related to the problems of antennas’miniaturization and bandwidth are still the hot spot in antenna field of study. With the improvement of electronics’performance, more and more new technologies come to practise from theory, and the bandwidth of antenna is also wider than before. In order to transform the energies of electricity and magnetism efficiently, it must fulfill certain size of antenna in design. In the shortwave band especially, the actual sizes of antennas are mostly large, that is also a difficult problem to achieve the goal of antennas’miniaturization. Recently, active antenna causes lots of antenna reserchers’attention, because it’s apt to realize the miniaturization of antenna, and can solve the problems of narrow bandwidth and low efficiency of passive electrical small antennas at the same time.Active antennas have many advantages compared with passive antennas, such as improving the gain of the antenna system, being convenient to match between the circuits and widening the bandwidth of antenna. But the part of active circuit can not only amplify the useful signal but also the unwanted noise because the introduction of active device. The active device is irreversible, so the active receiving antennas can not be used as the active transmitting antennas directly. In transmitting antenna system, the antenna radiation resistance is sensitive to operaiting frequency. Caused by the electric dimension’reduction of the antenna, the input impedance of antenna changes intensely with the frequency. Consequently, in active transmitting system, the bandwidth and output power are restricted seriously.Against to the problems of the bandwidth is not wide enough and the power capacity is restricted in shortwave band, a new solution is investigated in the paper. We design a negative impedance converter, through its function of impedance transformation the input impedance characteristics of the transmitting antenna is improved, so the bandwith of active transmitting antenna will be widen greatly. The simulation results show that, the negative impedance converter can not only reduce the impact of input reactance which is susceptible to the electrical length of the antenna, but also improve the input resistance, so that the input impedance of the active transmitting antenna won’t change with the frequency in short-wave band. It achieves a better match with the 50Ωcoaxial cable, and resolves the bandwidth problem of the active transmitting antenna in short-wave band.更多还原