Influence of Switching Power Supply Noise on the Magnetic Field Sensing of a High-Frequency Carrier-Type Magnetic Field Sensor

The authors demonstrated experimentally an influence of power supply noise on the magnetic field sensing of a high-frequency carrier-type magnetic field sensor. In magnetic sensing using such a magnetic sensor, an external ac magnetic field signal is modulated in amplitude in accordance with a high-frequency carrier signal. When a switching power supply is used for the carrier signal circuit, the power supply noise is also modulated in amplitude by the carrier signal. Therefore, both the upper and lower sideband spectra in the vicinity of the carrier signal are due not only to the magnetic field component but also to the power supply noise component. The sensitivity and frequency bandwidth of magnetic field sensing depend strongly on the noise level and noise frequency of the switching power supply.