Abstract
Magnetic flux vertical modulation method based on piezoelectric resonance can reduce the 1/f noise of tunnel magnetoresistance (TMR) magnetic sensor and significantly improves the low-frequency magnetic field detectivity. However, the amplitude variation of the modulation structure will lead to the instability of the sensor output. In order to improve the amplitude stability of the modulation structure, an amplitude control method based on the amplitude ratio of the first and second harmonic components of the modulated signal was proposed. Compared with the piezoelectric or capacitive feedback method, this method does not require an independent amplitude conversion circuit, and has the advantages of simple structure, high control efficiency and strong anti-interference ability. The experimental results showed that the amplitude and temperature drift of the modulated structure was significantly suppressed, which is of great significance for enhancing the adaptability of the TMR magnetic sensor to the application environments.
Highlights
tunnel magnetoresistance (TMR) magnetoresistance sensor has the advantages of high sensitivity, a large linear range and low power consumption
Scholars and research teams from different countries have proposed a variety of flux modulation methods to suppress the 1/f noise of TMR magnetic sensor, but these methods generally have problems such as low modulation efficiency, leading to the deterioration of noise characteristics, and poor environmental adaptability [4,5,6,7,8,9]
The magnetic flux vertical modulation method based on piezoelectric resonance has a high modulation efficiency of 68.7% [10], which can reduce the 1/f noise of the TMR magnetic sensor by nearly two orders of magnitude, and greatly improve the low frequency magnetic field detectivity
Summary
TMR magnetoresistance sensor has the advantages of high sensitivity, a large linear range and low power consumption. 1/f noise severely limits its low-frequency magnetic field detectivity [2,3]. The magnetic flux vertical modulation method based on piezoelectric resonance has a high modulation efficiency of 68.7% [10], which can reduce the 1/f noise of the TMR magnetic sensor by nearly two orders of magnitude, and greatly improve the low frequency magnetic field detectivity. The principle of magnetic flux vertical modulation based on piezoelectric resonance is shown as Figure 1. When the modulation film is far away from the air gap, the magnetic flux mainly passes through the TMR sensitive unit.
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