Parabolic Loci for Two Tuned Coupled Circuits

It is pointed out that the reciprocal of the system-response function E
1
/E
2,
or its equivalent, of conventional two-mesh tuned coupled circuits when plotted in the complex plane leads to parabolic loci under certain restrictions. The simple geometric properties of parabolas will facilitate the design work and may throw lights as to the applications and limitations of the coupled circuits in different fields, electrical or nonelectrical.