Almost Perfect Autocorrelation Sequences with Small Number of Pauses for Applications in Magnetic Resonance

It is well known that it is a challenge to find constant amplitude sequences with perfect autocorrelation over small alphabets. In this work we present a construction that provides sequences with perfect cyclic autocorrelation over different alphabets using the value zero only once or twice in their period. The constructions provide a big variety of periods also at moderate lengths and the corresponding sequences may be considered to be of ‘almost’ constant amplitude. These sequences have applications in NMR spectroscopy with low excitation power.