Space Difference Magnetic Near-Field Probe With Spatial Resolution Improvement

Abstract

To achieve good spatial resolution, small loop size is required in the traditional loop probe. However, the smaller loop size will lead to lower sensitivity for the probe. In addition, loop size is always limited by the minimum line spacing of the fabrication process. Another problem is that the asymmetric electric field coupling into a probe will not be canceled perfectly even if the structure of this probe is symmetric. To circumvent these problems, a space difference magnetic near-field probe with three kinds of spatial resolutions is proposed in this paper. The probe head including a one-turn loop and a two-turn loop is manufactured in low temperature co-fired ceramics (LTCC). The one-turn loop is clamped with the two-turn loop. Two loops are covered with two shielding ground plates to form a tri-plate structure. The received signals from these two loops are outputted with two SMA connectors through two striplines. The flip-chip junctions with low loss and good shielding capability are used between the probe head and the striplines. The probe characteristics are measured using a 436- μm-wide microstrip line with impedance of 50 Ω. Two output ports have different spatial resolutions because two different loops are located above the microstrip line at different height. The proposed probe will have higher spatial resolution when the received signals are outputted in difference. These results are also verified by measuring a 2000- μm-wide straight and a 500- μm-wide meander microstrip line. The experiment results have good agreement with the simulation results and show the resolution improvement of the difference output of the proposed probe for different lines.