Patent ID: 8680953

Claim:
A low-pass filter for electromagnetic signals, for limiting the passage of frequency ranges through a waveguide, characterized in that the waveguide or transmission line has a series of rejection elements, which are tuned to different frequencies determining a rejection band; wherein the rejection elements are defined by stubs of length λ g /4 and which have a sinusoidal, rectangular or any other arbitrary shape, being symmetrical or not with respect to a propagation direction; the low-pass filter being further characterized in that: the low-pass filter has the waveguide, wherein the waveguide has a rectangular section, and wherein upper and lower walls of the waveguide longitudinally define a perturbation of the rejection elements, having zero separation between them and accordingly facing one another, determining an inner envelope and an outer envelope which are variable, such that depending on a configuration of said inner and outer envelopes three consecutive longitudinal areas (A, B and C) having a different functional performance in relation to the electromagnetic signals passing through the inside of the waveguide are determined; and the longitudinal area (A) corresponding to an end inlet part of the filter is defined with the inner envelope which progressively decreases and with the outer envelope which progressively increases slightly.