Matching network design using non-Foster impedances

Abstract

Non-Foster synthesis bypasses the gain-bandwidth 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.

Electrically small metamaterial-inspired antennas with active near field resonant parasitic elements: From theory to practice

“…1. It replaces the traditional approach in which an external non-Foster matching network is employed [5]- [7]. Because it theoretically only modifies the reactance behavior of the input impedance, rather than both its resistance and reactance, it removes many of the drawbacks associated with the traditional external active-circuit matching approach.…”

Non-Foster matching network design for VLF receive loop antenna

“…4(b) according to literature [10]. This circuit cancels the reactance of the antenna by a negative inductance, and transforms the antenna's impedance to 50 Ω by a parallel negative capacitance and positive inductance.…”

“…Several NFCs' topologies have been proposed and analyzed in literatures [6,7,8,9]. Recent interests in this topic are the stability and sensitivity analysis of the NFC, which have been discussed by Sussman-Fort [10], Carson [11] and Justin [12] in HF (high frequency), VHF (very high frequency) and UHF (ultrahigh frequency). Over these frequency bands, different NFCs are matched to various types of antennas, such as monopole antenna [13], loop antenna [14], Egyptian axe dipole antenna [15], microstrip leaky-wave antenna [16] and parasitic array [17] etc., and beneficial results have been obtained.…”

Cognitive Radio and Networking Research at Virginia Tech

“…As an example of our ability to achieve the former, we have demonstrated front-end designs that are capable of expanding the effective (external noise-limited) sensitivity of dipole antennas from about 10% to about 25% using a front-end Bco-design[ strategy [67], [68]. We are seeking additional improvements using Bnon-Foster[ matching [69], which is a high-risk but high-payoff technique in which matching circuits are developed using active devices that achieve Bnonphysical[ impedance characteristicsVe.g., negative capacitanceVwhich result in dramatically improved impedance matching.…”