The receiver transforms and filters the input RF signals. Its output consists of one or more intermediate frequency bands, that we call IFs. These IFs are eventually then further processed by an IF processor that does another round of transformation and filtering bringing the signal to baseband for further use downstream. That input to the correlator is what we call baseband in this document and in CLIC . The correlator then processes the baseband in one or more spectral windows, that are a continuous set of adjacent channels sharing a correlator mode (including channel spacing). A given data set may hold spectral windows with different channel spacing though.