A method of effective use of ferrite for microwave absorber

To meet the demand for various electromagnetic-wave absorbers, a method for effective use of conventional ferrite in microwave absorbers is investigated both through finite-difference time-domain analysis and experiments. The matching characteristic is expanded to encompass a broad range from 1 GHz to over 4 GHz, using only a single magnetic material with a thickness of 6.5 mm. This is accomplished by simply punching small holes in a conventional magnetic absorber. The effects of various kinds of parameters for a rubber ferrite absorber with multiholes are clarified and general design charts are also presented, principally for normal incidence cases. The method of laser perforation is investigated for use in practical production. A desirable condition for obtaining a good matching characteristic in the present frequency range from 1 to 4 GHz is derived. A thin microwave absorber with a thickness of 3.0 mm at 2.45 GHz is presented as an application of punching small holes in a layer of conventional ferrite attached to a layer of carbonyl iron.