Electric field coupling suppression using via fences for magnetic near-field shielded-loop coil probes in low temperature co-fired ceramics

Two types of low-cost and robust magnetic near-field probes manufactured in low temperature co-fired ceramics (LTCC) are presented in this paper. The shielded-loop coil and via fences are used in the probes to provide better electric field coupling suppression. Type I probe is designed to receive horizontal magnetic field, via fences are inserted in the loop aperture and along sides of the probe to reduce electric field coupling from sides. The inner size of the loop aperture is 700×380 μm. The flip-chip bonding, which has low insertion loss and the good shielding capability, is also used in this probe. We take this probe over a 2000-μm-wide microstrip line as device under test (DUT) in measurements, the isolation between electric and magnetic field is better than 10 dB up to 11.5 GHz. The spatial resolution of the probe is 300 μm at 11 GHz. Type II probe is designed to receive the vertical magnetic field. The detected signal is passed along a right-angle channel surrounded by cylindrical via fences. Via fences are also set around the loop and give good shielding to reduce the electric field interference. The inner diameter of the loop aperture is 670 μm. For this vertical magnetic field probe, the measured minimum isolation between electric and magnetic field is 15.17 dB at 17.35 GH up to 20 GHz. The spatial resolution of this probe is 600 μm at 16 GHz.