Compact magnetic loop probe for microwave EM field-mapping and its applications in dielectric constant measurement

A novel compact CPW-type magnetic loop probe (2.3times2.3 mm) is proposed. Unlike the conventional one[1], the new probe move the impedance-transition to the CPW line part, so that the new probe possesses the property of symmetry (to suppress the influence of induced magnetic field created by the probe) as well as inherits/enhances the ability to suppress the loop self resonance(up to 10 GHz). Based on this probe, a 2.5D automatic vector near-field measurement system is developed by using the automatic network analyzer (ANA) as the signal detector. In this preliminary study, the magnetic field distribution of a section of short-circuited microstrip line and a square-loop type resonator are scanned by the novel probe. For reference, the electric field measurement results and theoretical ones by 3D simulator are all given. The good comparison between the measured results with the reference data shows the good performance of this probe. In addition, an extended study on extracting the effective dielectric constant of the substrate by our probe is also included with the experimental validation.