(a). Two mutually coupled LC tanks terminated with balanced gain on the left and loss on the right side G₁ = G₂ = G (b) real and (c) imaginary parts of evaluated eigenfrequencies by perturbing G. In the illustrated plots, only eigenvalues with the positive real parts are drawn. (d) The coalescence factor corresponding to calculated eigenvectors which showing the degeneracy of two eigenvectors exactly at G_e(e) Root locus of zeros of Y_in (ω) − G = 0 showing the real and imaginary parts of resonance frequencies of the circuit when perturbing both load resistance and gain G. At the EPD, the system’s total admittance is Y_in (ω) − G_e ∝ (ω − ω_e) ²; hence it shows a double zero at ω_e.