Matching network design using non-foster impedances

Non-Foster synthesis bypasses the gain-band width. limitations of conventional LC matching and achieves superior broadband performance by employing negative circuit elements, which are realized via negative impedance converters. The idea is to construct a negative-image model of an antenna, which cancels the antenna's parasitic reactance and transforms its frequency-dependent radiation resistance to a constant value. Successful implementation of negative-image modeling requires the realization of stable, low-loss negative elements. After a discussion of the basic ideas of non-Foster matching, we present experimental results for broadband, stable, high-Q, grounded negative capacitance. Next, in the first experimental confirmation of non-Foster impedance matching for signal reception, we use a floating negative capacitor to cancel a substantial portion of the reactance of a 6-in. monopole antenna. Over 20-110 MHz, the signal-to-noise ratio improved by up to 6 dB as compared to the same antenna with no matching, or to a lossy-matched blade antenna of twice the size. (c) 2006 Wiley Periodicals, Inc.