Novel high-spatial resolution probe for electric near-field measurement

A new probe with a micro-hole chip has been developed for measurement of near-field electrical radiation from printed circuit boards. The chip is fixed onto a semi-rigid cable probe facet and the radiated electric field is coupled with the surface of its inner conductor through an aperture with a diameter of 100 μm. Using a 50-μm-wide microstrip line for the device under test, we obtained a distance of 100 μm where the probe output decreases by 6 dB at a measurement height of 50 μm. This distance is in good agreement with our simulation results based on FDTD analysis. With a rectangular aperture of having a 50 μm width, we obtained a 72 μm distance at a 25 μm height. In addition, we confirmed that both the S21 characteristics of the measured line and the frequency characteristics of the probe can be dramatically improved by covering the outside of the probe with magnetic film.