LOW-PASS FILTER

摘要

A low-pass filter having an increased number of filter elements, a large coupling capacitance achieved even by a simple planar circuit, an attenuatio n pole near the passband, and a sharp out-band attenuation characteristic, wherein three or more open-end stubs having electrical lengths shorter than 1/4 of the wavelength of the passing frequency are so arranged parallel that the open ends are directed in the same direction, thereby forming a coupling line. At least one high-impedance line having a length shorter than the wavelength of the passing frequency is connected between the adjacent ends opposite to the open ends of the stubs.