High Density Interference Characteristics in Digital Magnetic Recording

The influences of medium parameters and recording level on the playback signal amplitude of high density digital magnetic recording have been experimentally examined. Several magnetic tapes with a thickness of 2.8 to 14μm were used for the experimental media. The playback signal amplitude from symmetrically recorded transition pattern was measured with varying recording transition density and recording current level. The transition density at which playback signal amplitude decreases to 50% of isolated signal amplitude, D_<50>, was noticed as a measure of overall resolution. The result of experiments can be summarized as follows : (i) The half amplitude density D_<50> is sensitive to recording current level in a thick medium, but this recording level dependency of D_<50> becomes less with decreasing medium thickness. (ii) The dependency of D_<50> on medium thickness δ can be approximately expressed as the form, D_<50>∽ δ^<-α>. The value of α depends on the recording level K. For example, α is about 0.8 and 0.3 for K is 2 and 0.5 respectively. (iii) As it can be expected from the superposing calculation of isolated playback pulses, D_<50> shows inversely proportional relationship to the half pulse width W_<50> of the isolated signal. The actual inversely proportional constant, however, somewhat differes from the calculated value.