A Closed-Type Planar Inductor

A planar inductor with a closed magnetic circuit structure is proposed. Whereas previous devices constructed by the authors consisted of a coil with magnetic layers above and below, in the present device the coil is surrounded by magnetic material on all four sides, for an increase in inductance from 100 nH to 200 nH. However, the bandwidth falls as a result, from 500 MHz to about 250 MHz. The increase in L is thought to be due primarily to the decrease in reluctance accompanying the addition of magnetic layers.