A concept of Q-varying digital IIR narrow bandpass filter with improved dynamic behavior

Many applications require narrow (single-frequency) bandpass filters (NBPFs) which possess both a very selective magnitude response (i.e. high quality factor Q) and a transient response of short duration. However, increasing the quality factor also increases the duration of the transient process in the filter after the action of the excitation. This paper presents a concept of digital IIR narrow bandpass filters whose quality factor changes with time. Owing to a temporary change in the value of the quality factor, the transient can be considerably reduced. Simulations verifying the effectiveness of the proposed Q-varying bandpass filter are presented and compared to the performance of the traditional Q-constant filter.