Decreasing the electric length of an antenna results in increasing its input reactance that becomes greater than its input resistance, resulting in a significant rise in its quality factor and in a drastic reduction of its potential operating bandwidth. For such small antennas, namely ESA for Electrically Small Antenna, passive matching is restricted by the gain-bandwidth theory, providing narrow bandwidths and/or poor gain. This limitation can be overtaken by using antenna matching networks based on non-Foster components. In previous studies, non-Foster components are used to cancel the reactance part of the ESA, and then passive matching may be introduced to transform the net input impedance toward 50Ω, which leads to an increase in the bandwidth. In this paper, a design methodology is put forward on three different topologies all based on combined passive and active matching networks. A described step-by-step design to decrease the antenna quality factor is discussed. A comparison is made between these topologies along with a discussion on their limitations and ability to increase the bandwidth and radiation efficiency of ESA. The third topology presented in this paper is a novel one that proposes a three-stage matching network and exhibits both the widest matched bandwidth and an increase in the efficiency of the whole system compared to previous approaches. In order to make this comparison, a new indicator to estimate the whole system radiated power efficiency is introduced and validated by comparison with a full EM simulation. Moreover, actual implementation of the two most interesting techniques are detailed and associated measured results are carefully compared to simulations.

减小天线的电长度会导致其输入电抗增加，该输入电抗变得大于其输入电阻，从而导致其品质因数显着提高，并且其潜在工作带宽急剧下降。对于这样的小天线，即用于电气小天线的ESA，无源匹配受到增益带宽理论的限制，从而提供了窄带宽和/或较差的增益。通过使用基于非福斯特分量的天线匹配网络可以克服此限制。在以前的研究中，非福斯特分量用于抵消ESA的电抗部分，然后可以采用无源匹配将净输入阻抗转换为50Ω，这会导致带宽增加。在本文中，提出了一种基于无源和有源匹配网络的三种不同拓扑的设计方法。讨论了减少天线质量因数的分步设计。对这些拓扑进行了比较，并讨论了它们的局限性以及增加ESA带宽和辐射效率的能力。本文介绍的第三种拓扑结构是一种新颖的拓扑结构，它提出了一个三阶段匹配网络，与以前的方法相比，它既显示了最宽的匹配带宽，又显示了整个系统的效率提高。为了进行这种比较，引入了一种估计整个系统辐射功率效率的新指标，并通过与完整的EM仿真进行比较来对其进行验证。此外，