The sensitivity of the (b), (d), (f) real and (c), (e), (g) imaginary parts of the eigenfrequencies to (b), (c) gyration resistance, (d), (e) positive capacitance C₁ (f), (g) positive inductance L₁ perturbation. Solid lines: solution of eigenvalue problem of equatoin (18); green-dashed lines: Puiseux series approximation truncated to its second term. Here, both resonators are unstable, i.e., resonance frequency of resonators is purely imaginary. Voltage v₁ (t) under the EPD condition in the (h) time-domain, and (i) frequency-domain. The frequency-domain result is calculated by applying an FFT with 10⁶ samples in the time window of 0 μs to 100 μs.