SEQUENCES AND A NEW CODE WITH SPECTRAL NULLS AT RATIONAL SUBMULTIPLESOF THE SYMBOL FREQUENCY

Auxiliary pilot tone insertion, used for positioning the servo of magn etic or optical disc recorders, requires codes that give rise to a spe ctral null at an arbitrary frequency. Sequences with asymmetrical runl ength constraints containing spectral nulls at rational submuitiples o f the symbol frequency are investigated. A sufficient condition for sp ectral nulls at rational submultiples of the symbol frequency is given in terms of a simple runnlength requirement A new code with rate=1/3 is presented with spectral nulls at the normalised symbol frequencies 1/4, 1/2 and 3/4.