An experimental study of the effect of thermal decay on noise and nonlinear distortions in perpendicular media

The time dependences of both noise and nonlinear distortions were studied using pseudorandom sequences. Transition noise and dc remanence noise were separated from the total media noise by curve fitting the transition noise with the most significant eigenmodes based on the Karhunen-Loeve expansion. The results show that the transition noise power and the signal decrease and the dc remanence noise power increases with time, resulting in a degradation of the total signal to noise ratio. Using the extracted dipulse technique, it was found that the main peak narrowed and a positive echo at 25-b position increased with time, which indicates that the decay of low-frequency components is faster than that of high-frequency components in perpendicular media.