Regressive discrete Fourier series

The term "regressive discrete Fourier series" doesn't correspond to a well-established concept in the fields of Fourier analysis or signal processing, as of my last knowledge update in October 2023. However, I can break down the components of the term to clarify what it might refer to: 1. **Discrete Fourier Series (DFS)**: This is an extension of the Fourier series concept to discrete signals.