JPS6429008A - Noise filter for high frequency wave - Google Patents

Abstract

PURPOSE:To obtain filter, which is small-sized, lightened in weight, of good mass- productivity and cheap, by using an oxide insulation layer, formed on the surface of magnetic material, as the dielectric of a capacitor, and constituting a filter by forming the capacitor on the magnetic material. CONSTITUTION:This noise filter is constituted of the magnetic material 11 of a cylindrical ferrite core, the oxide insulation layer 12, formed on the surface of the magnetic material 11, and electrodes 13, 14 and 17, formed respectively on the surface of the oxide insulation layer 12. The electrodes 13, 17 are formed on the outer circumferential surface of the magnetic material 11 at interval of a margin(m), and the electrode 14 is formed on the whole of the inner circumferential surface and the end surface of the magnetic material 11. Then, a conductor 15 penetrates the center of the magnetic material 11, and the electrode 14 is connected to the conductor 15, and the electrodes 13, 17 are connected to a metallic case 16, and they are hermetically sealed in the case 16. In this constitution, the insulation layer 12 acts as the dielectric of the capacitor, and one through-type capacitor is formed respectively between the electrodes 13 and 14 and between the electrodes 14 and 17. Then, by combining these plural capacitors and a coil element, consisting of the magnetic material 11 and the conductor 15, a pi type filter is constituted.