GB781088A - Radio-frequency inductor - Google Patents

Abstract

781,088. Impedance networks. BELLING & LEE, Ltd. Dec. 15, 1955 [Oct. 22, 1954], No. 30481/54. Class 40 (8). [Also in Group XXXV] An inductor having a high impedance over at least two dispersed frequency ranges in a band of radio frequencies consists of a plurality of spaced dissimilar windings connected in series and associated with a common core of magnetic material, the core and windings being fixed relative to one another, and so arranged and having such self-capacitances as to be resonant at a frequency within each of the frequency ranges. An inductor for suppressing interference of radio-frequency bands I and III in the power supply lines of an electrical appliance e.g. a vacuum cleaner, may comprise spaced coils 6, 7, Fig. 1, wound on an iron dust core having a permeability of about 5. To supplement the self-capacitances of the windings 6, 7, electrodes 4, 5, embedded in the core 1, are connected to the supply leads 2, 3. The electrical circuit of the device is substantially as shown in Fig. 3, in which C1, L1 are the self-capacitance and inductance, respectively, of the coil 6, C2, L2 are the self-capacitance and inductance, respectively, of the coil 7, C3 and C4 are the capacitances between the electrodes 4, 5 and the windings 6, 7, respectively, C5 is the capacitance between the two electrodes 4, 5, and M is the mutual inductance of the windings 6, 7. The circuit thus includes two parallel circuits resonant at different frequencies. In an alternative construction the magnetic core has two portions of different diameters upon which the two windings are mounted, and the electrodes are in the form of metal plugs fitted in recesses in the ends of the core.