Multi-stage electric filters with improved intermodulation-distortion
characteristics and a method for designing such electric filters is
provided. In general, the invention may include a multi-resonator
electric filter in which one or more of the resonators have been
intentionally designed to have a different IP and/or Q than the other
resonators in the electric filter. In one case, the electric filters
include a 4-resonator Chebyshev narrow pass-band filter with at least the
first resonator having a Q and/or IP different from at least one other
resonator in the filter. The filter thereby has improved IMD power over
conventional designed filters while maintaining high Q. In a preferred
embodiment the filter may include a superconducting material. The
relative Q and IP of the respective resonators in the improved filter may
depend on the relative strength of in-band and out-of-band signals. The
performance and cost of the electric filter may be optimized by designing
the filter to have a relative Q and IP required by the particular
application.