Applications of non-foster elements to design advanced RF and microwave devices

摘要

A specific frequency dependence of reactance of negative inductances and capacitances give opportunities to overcome limitations of conventional RF and microwave devices with regard to the operational frequency band. Since such frequency dependence cannot be obtained from a passive circuit according to Foster's theorem, active circuits known as negative impedance converters (NICs) are used to realize negative inductances and capacitances which are therefore called non-Foster elements. Design issues of NICs and promising applications of non-Foster elements in RF and microwave devices with extended operational bandwidth are discussed in the paper. Frequency characteristics of NICs based on transistors of different kind are analyzed.