Efficiently Cascaded Interpolation Filters and their Implementations in FPGA´s

This paper describes an efficient way to implement interpolation filters for spectral forming of time-discrete signals. Using Lagrange interpolation, it is even possible to perform fractional delay adaptation. In order to reach an adequate spectral attenuation for digital modulation, it is necessary to use high-order filters. The implementation of these filters would increase the consumption of logical elements in FPGA´s. Due to the high complexity of Lagrange interpolation, the needed fractional delay filters do not represent an acceptable solution. To find a remedy to this problem, various kinds of filters have to be cascaded. This is what will be illustrated in this paper, by also giving an example. In particular, it is always necessary to look for a compromise between the coupling´s profitability and the essential attenuation of undesired spectral components needed for a good transmission