Realizing Non-Foster Reactive Elements Using Negative-Group-Delay Networks

Abstract

An intimate relation is established between non-Foster reactive elements and loss-compensated negative-group-delay (NGD) networks. It is shown that any possible network configuration containing a class of non-Foster elements operates as an NGD network. Likewise, it is demonstrated that a loss-compensated NGD network represents a reactive network with a non-Foster behavior. Consequently, these two properties can be intimately linked together and NGD networks can be utilized to implement non-Foster elements, such as negative capacitors and inductors. This result introduces another perspective in realizing non-Foster reactive elements, leading to new designs that are well behaved and more predictable in terms of stability and operation than traditional designs using negative impedance inverters and negative impedance converters. Based on this concept, loss-compensated NGD networks are proposed for realizing high-quality non-Foster reactive elements. Furthermore, entirely passive non-Foster elements with a limited quality ( ) factor are proposed for which the minimum factor and the maximum achievable bandwidth are inversely related. It is shown that the design of non-Foster reactive elements using NGD networks can lead to the realization of standalone unilateral non-Foster reactive elements in a certain bandwidth. Examples of such non-Foster reactive elements and networks are demonstrated experimentally and shown to be stable.Index Terms-Dispersion engineering, negative group delay (NGD), negative group velocity (NGV), non-Foster reactances.

Negative Group Delay Phenomenon Analysis Using Finite Unloaded Quality Factor Resonators

“…Therefore, conventional approaches to realize the NGD circuits are based on bandstop structures using either series or shunt RLC resonators [4][5][6][7][8][9][10][11]. The NGD circuits have been used in various practical applications in communication systems, such as shortening or reducing delay lines [11], enhancing the efficiency of feedforward linear amplifiers [12,13], designing broadband and constant phase shifters [14], realization of non-Foster reactive elements [15], and minimizing beam-squint in series-fed antenna arrays [16].…”

Novel design of a 2.1–2.9 GHz negative capacitance using a passive non-Foster circuit

“…Based on the relation between properties of negative elements and negative group delay (NGD), shown in the Fig. 1, Hassan Mirzaei [5] analyzed and designed a new high Q NFC without using a loop inside the circuit. However, NGD, in his design, suffers much loss parameter; even when using an effective gain amplifier.…”

A Miniaturized Self-Matched Negative Group Delay Microwave Circuit

“…One of the adopted solutions to compensate the group delay is utilizing negative group delay (NGD) circuits [5]. Recently, the characteristics of NGD circuits have been applied to various communication systems, such as neutralizing the disturbing effects produced by LC -and RC -networks [6,7], shortening or reducing delay lines [8], increasing the efficiency of feed-forward linearization amplifier [9], enhancing the bandwidth of analog feedback amplifier [10], minimizing the beam-squint in phased array antenna systems [11], and realizing the non-Foster reactive elements [12].…”

“…In microwave circuits, series and parallel RLC resonators are widely used to achieve NGD phenomenon [8][9][10][11][12][13][14][15]. Most of them are used in the reflection-type NGD circuit.…”

“…Most of them are used in the reflection-type NGD circuit. For reflection-type NGD circuits, an extra component, such as a hybrid coupler is always needed to convert these circuits to transmission-type circuits and realize port matching [12][13][14][15]. In addition, some RLC resonators are used in the transmission-type NGD circuit with the filter synthesis approach [16].…”