Design of multilevel pseudorandom signals for specified harmonic content

Pseudorandom signals have been used as test signals in system identification for many years. The most common application is the identification of linear systems using pseudorandom binary signals, which have excellent correlation properties for this purpose. In contrast, the harmonic properties of pseudorandom signals are less well known than their correlation properties. Consequently the harmonic properties of these signals have been less well exploited in system identification. In the paper, the harmonic properties of pseudorandom signals are shown to depend on fundamental properties of the maximum-length m-sequences from which they are derived by mapping, and on the nature of the mapping itself. In particular, it is shown that both the m-sequence and the mapping can be chosen to provide the pseudorandom signal with a specified harmonic content