Patent ID: 7859364

Claim:
A layered low-pass filter comprising: a layered substrate including a plurality of dielectric layers stacked; an input terminal provided on a periphery of the layered substrate and receiving signals; an output terminal provided on the periphery of the layered substrate and outputting the signals; a first coil and a second coil each of which is formed using at least one conductor layer provided within the layered substrate, the first and second coils being connected in series to each other, each of the first and second coils having an input for receiving the signals and an output for outputting the signals and, in terms of circuit configuration, the first and second coils located between the input terminal and the output terminal and the first coil being located closer to the input terminal than is the second coil; a capacitor formed within the layered substrate and, in terms of circuit configuration, located between a ground and a node between the first and second coils; a first conducting path that is formed using at least one through hole provided within the layered substrate and that is used for connecting the capacitor to the output of the first coil; a second conducting path that is formed using at least one through hole provided within the layered substrate and that is used for connecting the capacitor to the input of the second coil; and a third conducting path that is formed using at least one through hole provided within the layered substrate and that is used for connecting the capacitor to an end of each of the first and second conducting paths closer to the capacitor, wherein the first conducting path and the second conducting path are arranged such that directions of currents flowing through them are opposite to each other, and are magnetic-field-coupled to each other, the first and second conducting paths have equal lengths, and the third conducting path has a length equal to or smaller than one-half of the length of each of the first and second conducting paths, and the layered low-pass filter presents at least one attenuation pole in a stop band in a pass attenuation characteristic.