Planar Coil Inductor with Closed Magnetic Circuit

A break in the electrical or the magnetic path in a conductor or magnetic core is a serious problem for the fabrication of inductors. A planar-coil inductor with a closed magnetic circuit is proposed, and its characteristics are described. The conductor of the planar-coil inductor is patterned on a plane, in order to prevent the occurrence of disconnections in the conductor. To decrease the magnetic resistance, the cross-sections of core junctions, at which there is the risk of disconnection, are regulated. A trial-fabricated inductor consisted of one hundred magnetic cores, each of size 180 ¿m × 180 ¿m. The inductor dimensions were 2.3×2.3 mm². The inductance of the device was 50 nH, and the resonance frequency was about 400 MHz.