Fig. 5: FFT spectrum of the output signal at a dual-frequency (107.043 kHz and 107.049 kHz) driving at different input levels.
a Input level –3 dBm, and b input level 4.5 dBm. \(\varDelta f=f/{f}_{0}\) is the difference between the operation frequency f and the central frequency f0 (107.046 kHz)
