Development of a magnetic field probe for near-field measurement

Abstract

Current electronic circuits are characterised by their compact design of miniaturisation; however, such a feature has also contributed to the rise of electromagnetic compatibility issues. This study introduces a technique to develop a magnetic field probe for near-field measurement. The probe aims at performing the debugging of electromagnetic interference on an integrated circuit. Certain processes, such as designing a microstrip line in simulation and a prototype for the validation as well as developing a functional magnetic field probe for near-field scanning and calibration measurement to determine the probe factor, have been performed under a frequency domain. The microstrip line model is built both as a simulation and a real prototype, and the handcrafted loop probe is developed with the same diameter as a commercial probe. Calibration measurement is set-up with a vector network analyser (VNA) to capture the magnetic field on radiated plane. The performance of the handcrafted probe in terms of measuring the configuration of the H-field source on the scattering region is conducted. Two types of measurements which are S11 and S21 will be conducted using a VNA. The comparison of the S11 and S21 results against simulation results are plotted using MATLAB. S11 represents the return loss of the microstrip line while S21 represents the power received by the magnetic field probe relative to power input to the microstrip line. The results of the S11 parameter indicate that the customised microstrip line board has a similar waveform pattern that matches the one on the simulation model. The S21 results for the handcrafted probe revealed that it can only function well up to the frequency of 2.644 GHz, the abnormal result obtained after the frequency mentioned. Some factors may have affected the results, such as material loss, fabrication tolerance and interferences from other devices. Therefore, calibration measurement is conducted under a less reflected radiation environment, and the designated substrate should be a perfect material correlated with the measurement.