Realization of Dual Mode Band Rejection Filters

Band-rejection filters comprise a set of resonant circuits connected to a transmission line and to each other, such that an undesired band of frequencies is selectively removed from the incident spectrum. Commonly, the resonant circuits take the form of cavities, which are iris-coupled to a main line. The cavities are spaced an odd multiple of lambda g/4, where lambda g refers to the main line guide wavelength. This spacing results in properly phased addition of the attenuation due to each resonant cavity. The amount of attenuation contributed at any frequency is set by the coupling iris, and is pre-determined by the particular network synthesis utilized.