Asymmetric parallel-coupled CPW stages for harmonic suppressed λ/4 bandpass filters

A four-pole λ/4 coplanar waveguide (CPW) bandpass filter, terminated with two asymmetric parallel-coupled stages, is proposed. By separately allocating the two unequal transmission zeros, the spurious response at the triplicate passband frequency (3f 0 ) is suppressed. Simulated and measured results confirm the attractive features of this proposed filter, i.e. wide passband and good harmonic suppression.