Interdigital filter with coupled resonators of decreasing impedance - consists of stepped or pref. continuously tapered strips of metallisation extending across midline of dielectric substrate

摘要

A stripline- or microstrip-structured metallisation (M) on the dielectric substrate (S) forms an even number of resonators (R) with input and output taps (P) on the first and last members of the cascade. In a pref. embodiment the input resonator and its immediate neighbour are tapered outwards from their roots towards their free ends. The remaining two resonators are of the conventional uniform width and impedance, constituting a multipole band-pass filter. ADVANTAGE - Suppression of higher-freq. passbands is improved with first repetition freq. raised from three to nearly four times fundamental.