Polyphase filters comprise a plurality of filters each filter having
passive elements. The filters are provided with integrators comprising
amplifiers with admittance elements in feedback paths to create one or
more other poles not situated on the negative imaginary axis in the
plane-zero plot. A conductance element couples an output of an integrator
of the integrators to an input of a previous integrator for introducing a
frequency shift for at least one pole in the plane pole-zero plot. A
capacitor couples an output of the integrator to an input of a next
integrator for improving the quality factor of the polyphase filter. A
signal inversion allows conductance elements to have negative values
necessary for locating at least one pole at the most optimal location in
the plane pole-zero plot.