In this paper, a high resolution magnetic measurements are performed in an AES (advanced encryption standard) cryptographic FPGA by using a newly designed magnetic probe. The probe consists of high resolution
scanning system and magnetic field collecting coil integrated with 3-stage low noise amplifier to enhance the sensed voltage. Also, to improve the performance of the magnetic coil, the Si-substrate is removed under the
coil by using FIB process. The results and discussion section clearly shows that, the proposed magnetic probe gives more detailed information about the susceptible area of an AES cryptographic FPGA surface with high
resolution maps in different frequency bands compared with the existing magnetic probe.