Input Admittance Characteristics of a Tuned Coupled Circuit

A steady-state analysis is given of an important double-tuned coupled circuit to determine the input admittance when the primary Q is high and the secondary Q is low. Particular emphasis is placed on the phase variation of the admittance with frequency. Dimensionless curves of magnitude and phase illustrate the effect of varying the coefficient of coupling and the secondary Q. Mathematical expressions are obtained for the points where the phase passes through zero, and are used in a discussion of bandwidth. The effect of detuning is also considered.