An optical-waveguide-type magnetic field probe with a loop antenna element

We measured the magnetic field signal near a printed circuit board and examined an optical-waveguide-type magnetic field probe with the object of knowing the current signals flowing in the wires, the crosstalk between the wires, and the radiated noise source without affecting the operating state of the circuit. The frequency response of the probe head was analyzed based on an equivalent circuit model, and the relationship between the antenna setting parameters and the probe characteristics was explained. Next, a probe was designed and fabricated, and its properties evaluated with the objective of proving the operation of magnetic field detection in the cellular phone and wireless LAN frequency bands. Frequency characteristics and magnetic field/electric field sensitivity ratio characteristics similar to those of the equivalent circuit model were seen in the electromagnetic field measurements with a Horn antenna as the transmission source. Magnetic field detection near a microstrip line was also confirmed. (c) 2005 Wiley Periodicals, Inc.