摘要:
In a coaxial filter arrangement having a plurality of coaxial resonators each having a bottomed metallic cylinder interposed between a dielectric plate and one end of a center conductor of each resonator, the peripheral wall portion of the metallic cylinder is received in the bore of an outer conductor having an open end and a closed end connected to the other end of the center conductor. In one embodiment, the bottom of the metallic cylinder has a convex portion at its center so that the bottom center projects outwardly. In another embodiment, an annular metallic member is interposed between the dielectric plate and the outer surface of the flat bottom of the metallic cylinder. Since the distance between bottoms of metallic cylinders of adjacent resonators is made large with this arrangement, influence due to leakage flux of electromagnetic field is small, while stray capacitance is negligibly small, thereby providing a filter having high performance and low loss.
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.