Cascaded-Dispersed-Resonator-Based Off-Nominal-Frequency Harmonics Filtering

Harmonics filtering for nominal frequencies is well-known and plain task. Discrete Fourier transform (DFT), Taylor–Fourier transformation (TFT), and cascaded integrator–comb (CIC) filters are some of the widely used digital signal processing techniques. However, in case of frequency deviation, this task becomes much more complex. The reason is that the harmonic frequency deviation from the nominal one is proportional to the harmonic order. This article proposes the cascaded-dispersed-resonator (CDR)-based filter technique for off-nominal frequency harmonics analysis, similar to the multiple-resonator (MR)-based filters. The technique previously used for the synthesis of the so-called quasi MR-based filters is applied. Unlike the previous intention to design filters with frequency responses as much close to true MR filters as possible, which caused putting poles in the cascade as much close to each other as possible, here it is necessary to place poles with a displacement width necessary to cover the whole band of the fundamental frequency deviation proportional to the orders of the harmonics.