When the acousto-magnetic tag enters the alternating magnetic field (detection area) excited by ASK and the tag's resonance frequency is consistent with the carrier frequency, resonance will occur in the tag due to the magnetostrictive effect.
When the exciting alternating magnetic field is turned off, the resonance signal will be maintained for a period of time according to the piezomagnetic effect of the tag, and there will be damped oscillation; in addition, since the mechanical energy and the magnetic field energy are alternately converted, the resonance signal is a kind of acousto-magnetic composite signal , Is the meaning of the acousto-magnetic system.
The resonance signal not only serves as the spatial extension of the excitation magnetic field, but also has the characteristics of ultrasound. Therefore, the induction coil in the receiver can easily detect the resonance signal to drive the alarm device of the system.