Analysis of a periodically time-varying digital filter

This paper proposed two models of a periodically time-varying digital filter. One model is similar to a polyphase digital filter (polyphase model) and the other a coefficient-varying model. These models are different essentially. However, it was proved that under certain conditions, filters described by the coefficient-varying model is equal to the polyphase model. Moreover, it was shown that the relationship between the power of an input signal and of an output signal in a periodically time-varying digital filter, which correspond to the well-known Manly-Row law in an analog time-varying circuit was derived.