Magnetoelectric (ME) antennas have offered significant advantages in the design of very-low-frequency (VLF) communication systems operating in challenging environments such as underground, underwater, and inside metallic enclosures. However, state of the art ME-based communication systems either depend on bulky commercial signal processing instruments or have limited reports on digital signal transmissions. In this work, we demonstrate a compact design of an ME VLF communication system based on self-designed modulator and demodulator circuits, working at the electromechanical resonance frequency of the ME antenna and having a remarkably reduced size for greater applicability in realistic industrial scenarios. The concept of sending Morse code through amplitude-shift-keying modulation was confirmed in the proposed ME VLF communication system. Our findings revealed that the maximum communication distance can be considered as 5.7 m when the bit-error-rate is limited to 10 ^-2 . Furthermore, VLF wireless signal transfer through a harsh environment (metal box) was verified with our communication system. An effective communication distance of 0.85 m could be realized when placing the ME receiver in a 5 mm iron box, demonstrating the ability of the wireless signal to penetrate conductive media. The proposed fully packed ME VLF communication system provides advantageous alternative for underground, underwater, and inside-metal-containers communications.

Magnetoelectric (ME) sensors cannot effectively detect broadband magnetic field signals due to their narrow bandwidth, and existing readout circuits are unable to vary the bandwidth of the sensors. To expand the bandwidth, this paper introduces a negative-feedback readout circuit, fabricated by introducing a negative-feedback compensation circuit based on the direct readout circuit of the ME sensor. The negative-feedback compensation circuit contains a current amplifier, a feedback resistor, and a feedback coil. For this purpose, a Metglas/PVDF/Metglas ME sensor was prepared. Experimental measurements show that there is a six-fold difference between the maximum and minimum values of the ME voltage coefficients in the 6–39 kHz frequency band for the ME sensor without the negative-feedback compensation circuit when the sensor operates at the optimal bias magnetic field. However, the ME voltage coefficient in this band remains stable, at 900 V/T, after the charge amplification of the direct-reading circuit and the negative-feedback circuit. In addition, experimental results show that this negative-feedback readout circuit does not increase the equivalent magnetic noise of the sensor, with a noise level of 240 pT/√Hz in the frequency band lower than 25 kHz, 63 pT/√Hz around the resonance frequency of 30 kHz, and 620 pT/√Hz at 39 kHz. This paper proposes a negative-feedback readout circuit based on the direct readout circuit, which greatly increases the bandwidth of ME sensors and promotes the widespread application of ME sensors in the fields of broadband weak magnetic signal detection and DBS electrode positioning.

The majority of traditional eddy current-based metal film thickness measurement systems measure the thickness of the metal film by detecting changes in the impedance or voltage of the detection coil, leading to limited measurement range and susceptibility to measurement errors caused by variations in lift-off distance. This article proposes a method for metal film thickness measurement across a wide range using a high-performance magnetoelectric (ME) sensor to directly detect the total magnetic field of the excitation field and the induced field. Numerical calculations based on the eddy current magnetic field model reveal a highly linear relationship within a specific range between this total magnetic field and the logarithm of the metal film thickness. If the detectable magnetic field range of the magnetic field sensor covers 32–51 nT with a bandwidth of up to 1.5 MHz, theoretically, the measurement of copper film thickness within the range of 0.65 nm–1000 $\mu$ m can be achieved by adjusting the excitation magnetic field frequency, and the measurement error introduced by the lift-off distance can also be ignored. The experimentally prepared ME sensor, covering a range of 30 pT–100 nT within a bandwidth of 1.5 kHz–1.5 MHz, was used to construct a metal film thickness measurement system. Measurements on copper films with thicknesses ranging from nanometers to micrometers, under excitation fields at six different frequency excitation fields within the range of 1.5 kHz–1.5 MHz, exhibited measurement errors within 1%, confirming the feasibility of this method for a wide range of copper film thicknesses from 60 nm–350 $\mu$ m.