A new characteristics-varying two-input/output filter in D-module-designs, realizations and equivalence

This paper proposes a new n-th order two-input/output filter in a module for two-phase signal processing. The filter can make a distinction between positive and negative frequencies of two-phase signals and can allow one to process the signals based on frequency-polarity. The filter can also change dynamically its filtering characteristics by simply injecting a shift-signal to the filter. Filtering effects equivalent to ones by parallel arranged filters with vector rotators can be obtained, but in a much simpler manner. A total of unified analyses of attractive general properties of the proposed filter is also given for easy designs and realization. The effectiveness of the analyses and usefulness of the filter are examined and confirmed through experiments. The proposed two-input/output filter in module has potential usefulness to a variety of polyphase signal filtering applications including sensorless vector controls of three-phase AC motors that require to process positive or/and negative sequences based on frequency and polarity.