Wideband Bandpass Filter With Extremely Wide Upper Stopband

The realization of planar wideband bandpass filters with an extremely wide upper stopband is described. The filter design differs from conventional approaches in which it is based on the choice of a wideband bandstop (BS) filter, to which a number of shunt-shorted stubs are connected at specific nodes; the stubs provide transmission zeros at the origin. Two examples of wideband bandpass filters with extremely wide upper stopbands are presented: filters based on a fifth-order Chebyshev wideband BS filter and a pseudoelliptic function ultra-wideband-BS filter. Relative passbands in excess of 100% are achieved, while the equivalent of at least four harmonic passbands is suppressed.