Patent ID: 6177849
Filing Date: 2001-01-23
Classification: H04B

Abstract:
A power line communications filter for extracting signal frequencies of at least 1 MHz from power lines, comprising an input terminal, an output terminal, and a common terminal; a transformer having primary and secondary windings, each having one end connected to said respective input and output terminals, and another end connected to a common connection, said windings being wound on a high permeability magnetic core having, a permeability of at least about 800 up to a frequency of about 5 MHz in such a way as to promote flux leakage and with a winding polarity such that the flux in each winding cancels out the flux in the other winding when current flows through said windings in series; and a first capacitor between said common terminal and said common connection of said primary and secondary windings, said first capacitor having a large impedance at low frequencies such that low frequency current flows through both said windings in series and flux cancellation occurs, a second capacitor between said output terminal and said common terminal to increase attenuation at high frequencies, and a third capacitor to extract said high frequency signals at said input terminal, said third capacitor acting as a high pass filter, and said transformer forming with said first capacitor a resonant circuit at frequencies in the order of 1 to 5 KHz.