Unilateral non-Foster elements using loss-compensated negative-group-delay networks for guided-wave applications

Mirzaei, Hassan; Eleftheriades, George V.

doi:10.1109/mwsym.2013.6697608

Cited by 11 publications

(16 citation statements)

References 14 publications

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“…We briefly presented the relation between NGD networks and non-Foster reactive elements along with a unilateral floating non-Foster capacitor implementation in [31]. We proposed an application of such non-Foster elements in squint-free series-fed antenna arrays in [32].…”

Section: Introductionmentioning

confidence: 99%

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

Mirzaei

Eleftheriades

2013

IEEE Trans. Microwave Theory Techn.

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113

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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.

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Section: Introductionmentioning

confidence: 99%

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

Mirzaei

Eleftheriades

2013

IEEE Trans. Microwave Theory Techn.

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113

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“…When loss compensation is performed using unilateral active devices, special kinds of reactive non-Foster elements, called unilateral reactive non-Foster elements, can be obtained, and the stable operation of these unilateral non-Foster elements has been shown in [8]. These unilateral elements are useful and even beneficial for guided-wave applications where waves need to travel only in a certain direction [7].…”

Section: Implementation Of Fast-wave Feedlines Using Unilateral Rementioning

confidence: 99%

“…3(b). With the further assumption that there is no propagation in the reverse direction, the stable unilateral version of the non-Foster reactive elements can be employed, as proposed for guided-wave applications in [7]. In fact, an implementation of a unilateral non-Foster T-network has been presented in [8].…”

Section: Implementation Of Fast-wave Feedlines Using Unilateral Rementioning

confidence: 99%

“…To overcome these stability challenges, and to be able to implement electrically-long structures suitable for feed-network applications, the authors have recently proposed an alternative design methodology for non-Foster reactive elements using loss-compensated negative-group-delay (NGD) networks [7], [8]. This approach is developed by observing that non-Foster reactive elements and NGD networks influence propagating waves in a similar fashion.…”

Section: Introductionmentioning

confidence: 99%

“…When using regular unilateral amplifiers to compensate losses, special kinds of reactive non-Foster elements, called unilateral non-Foster elements, can be obtained which are suitable for guided-wave applications (e.g. the application in this paper) [7]. Stable and wideband operation of these unilateral non-Foster elements has been demonstrated in [8].…”

Section: Introductionmentioning

confidence: 99%

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Arbitrary-Angle Squint-Free Beamforming in Series-Fed Antenna Arrays Using Non-Foster Elements Synthesized by Negative-Group-Delay Networks

Mirzaei

Eleftheriades

2015

IEEE Trans. Antennas Propagat.

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107

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Beamforming in series-fed antenna arrays can inherently suffer from beam-squinting. To overcome the beamsquinting problem, low-dispersion, fast-wave transmission lines can be employed. Such transmission lines can be designed by loading a regular transmission line with non-Foster reactive elements (e.g. negative capacitors and inductors). As a result of a recent development, these non-Foster reactive elements can be implemented using loss-compensated negative-groupdelay (NGD) networks, providing a solution to the stability issues associated with conventional non-Foster networks. In this work, transmission lines augmented by loss-compensated NGD networks, representing the non-Foster reactive-element loading, are employed for designing wideband fast-wave, lowdispersion transmission lines. This work consolidates this non-Foster reactive element loading method with earlier efforts where NGD networks were used to implement zero-degree phase shifters for beamforming at the broadside direction, and generalizes these methods for arbitrary-angle beamforming from backfire to endfire including the broadside direction. Experimental results are presented for a wideband linear four-element transmitting array feed network for beamforming at 30 o with respect to the broadside direction in the frequency range of 1 to 1.5 GHz. By connecting this feed network to four wideband taperedslot antennas, the beamforming performance is experimentally verified inside an anechoic chamber. Moreover, the antenna array is experimentally tested for transmission of a narrow pulse, where low distortion is observed at the beamforming angle over the entire operating bandwidth. The physical length of the feed network is realistic and is 0.96 wavelengths long at the center of this frequency range. In addition, switched-line phase shifters are employed for squint-free beamforming in three other angles, namely-60 o , 0 o and -30 o .Index Terms-Non-Foster reactances, linear antenna arrays, antenna feeds, negative group delay (NGD), negative group velocity (NGV), dispersion engineering. 0018-926X (c)

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