Optimum waveform design and its effect on the peak shift compensation

An equalization method of reducing peak shift caused by the intersymbol interference is presented to obtain high density digital magnetic recording. First, a new ideal frequency characteristic is determined to get an impulse response free from peak shift. Then, using the equalizer that gives this response, the extent of the peak shift compensation is simulated with a computer. When a 2200BPI (FM) disk unit is used to double the bit density with MFM, it is found that the peak-shift in the worst case is only 8.4% of the full phase margin. Here, other parameters such as RPM, remain constants. However, as the application of the equalizer increases the noise power, signal to noise ratio of the input signal is required to be sufficiently high. When the equalizer is applied to a 4040BPI (MFM) disk unit at the same density, phase margin for data separation increases, because the decrease in peak shift seems to be greater than the increase in the noise power.