Detecting defects on planar circuits by using non-contacting magnetic probe

Recently, the research of non-contacting measurement with magnetic coupling theorem mostly choose CPW(coplanar waveguide) loop-type circuits as probes. It has advantage of low cost, easy to fabricate and simple designing. While moving the probe, different relative position between planar circuit and magnetic probe cause different strength of coupling. Variation of resonance frequency due to changing magnetic coupling and electric coupling from metal strip outline can be observed. The relation between planar circuit and magnetic probe is analyzed by full-wave EM simulation and some simple measurement. Furthermore, the LC equivalent circuit has also been built for analyzing. At last, the possibility of doing quickly defect-detecting by sweeping the circuits at special frequency will be discussed.