Abstract-During the last years many researchers have been working on the active matching or on non-Foster matching networks for one-and two-port electrically small antennas (ESAs). A new parameter on the sensitivity of the two-port electrically small antenna when loaded with a non-Foster network is presented. This sensitivity analysis will allow us to choose what kind of antennas can be properly matched with non-Foster networks and their position in order to optimize the performance of the design. Then, a typical high Q two-port antenna will be harder to match over a broad bandwidth, since |s 21 1 is very small and only agrees with |sn| over very small frequency bands, yielding very large sensitivity values. However, for these two-port antennas, if high levels of coupling can be engineered for a high Q multiple-port antenna, the return and insertion losses can be similar over larger bandwidths and, hence, the sensitivity can be kept low over larger bandwidths, enabling broader impedance matched bandwidths to be achieved, even for highly resonant antennas.

The design of electrically small antennas loaded with active non-Foster elements is a topic whose interest has grown in the last years. In this paper, a new strategy for the design of actively matched antennas loaded with non-Foster elements is presented. The analysis of different parameters, such as the sensitivity to non-Foster circuit placement, the overall antenna system stability and current distributions, has to be considered in order to enhance the antenna performance. A design example using an electrically small antenna (ESA) and its realization is presented to validate the proposed strategy.

Abstract. Negative impedance converters (NICs

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