@ARTICLE{ iet:/content/journals/10.1049/el.2015.1429, author = {A.A. Muller}, affiliation = { Microwave Applications Group, iTEAM, Universidad Politehnica de Valencia, Valencia, Spain }, author = {S. Lucyszyn}, affiliation = { Department of Electrical and Electronic Engineering, Imperial College London, Exhibition Road, London, SW7 2AZ, United Kingdom }, keywords = {driving-point reactance;network theory;driving-point susceptance;negative inductance;reactive Foster network;capacitance element;frequency gradient;nonFoster passive network;positive inductance;driving-point immittance;}, ISSN = {0013-5194}, language = {English}, abstract = {The mathematical concept of strongly real functions of positive and negative types is introduced to network theory for the first time. The driving-point reactance/susceptance of a pure Foster network, made up of only ideal positive inductance and capacitance elements, is a strongly real function of real frequency of positive type. As a corollary, for a pure non-Foster network made up of only ideal negative inductance and capacitance elements, the driving-point reactance/susceptance is a strongly real function of real frequency of negative type. It is shown that a condition for a purely reactive passive network to exhibit a positive or negative reactance/susceptance-frequency gradient is that the driving-point immittance should have alternating poles and zeroes lying on the real frequency axis. Finally, it is shown that either purely Foster or non-Foster networks can be constructed by combining ideal Foster and non-Foster reactive elements.}, title = {Properties of purely reactive Foster and non-Foster passive networks}, journal = {Electronics Letters}, issue = {23}, volume = {51}, year = {2015}, month = {November}, pages = {1882-1884(2)}, publisher ={Institution of Engineering and Technology}, copyright = {© The Institution of Engineering and Technology}, url = {https://digital-library.theiet.org/;jsessionid=h6x98t9c82zt.x-iet-live-01content/journals/10.1049/el.2015.1429} }