Band-stop filter for VHF-UHF band

摘要

A band-stop filter for VHF-UHF band comprises at least three series resonance circuits and at least two transmission lines each connected between the series resonance circuits. One of the transmission lines, which is connected to the input terminal of the band-stop filter, has an electrical length which is shorter or longer than the quarter wavelength of the center frequency of the stop band by more than 20 but less than 50 percent. When a band-stop filter comprises four transmission lines, one of the transmission lines, which is connected to the output terminal of the band-stop filter, has the same length as the transmission line connected to the input terminal. With this arrangement, the band-stop filter exhibits a sharp attenuation characteristic in a frequency range below or above the center frequency. Other transmission lines, which are not directly connected to either the input terminal or the output terminal, may have a length which is shorter or longer than the quarter wavelength by 5 to 20 percent so as to provide a sharper attenuation characteristic.