Experimental study of signal-dependent noise in metal particle tape

We have measured and analyzed signal-dependent noise spectra of metal particle (MP) tapes. For all the tapes examined, the signal-dependent noise is higher than the DC saturation noise. The total signal-dependent noise power first increases with density and then saturates. The measurement indicates that without write equalization, the broad-band signal-dependent noise power increases with recording density, indicative of transition noise. With write equalization, the broad-band signal-dependent noise is approximately independent of density and has a level equal to the high density limit without write equalization. We used a specially designed pattern to eliminate tape speed variations and find the precise recording positions. We used a Karhunen-Loeve expansion with the time-domain data to determine the noise modes and their recording density dependency. The analysis shows that amplitude and jitter modes dominate for all the MP tapes examined. Different noise mode contributions are observed for different coating thicknesses. The amplitude mode dominates for relatively thick coatings, while the jitter mode dominates for thin coatings, as in thin-film disk media.