Chapter 3 - Read process in magnetic recording

Abstract

This chapter discusses important aspects of the readback process in magnetic recording―the reciprocity principle for calculating readback signal and derivation of the readback voltage pulses of various types of magnetic transitions. When a magnetic recording medium with written magnetic transitions passes underneath an inductive recording head, the magnetic flux produced by each transition is picked up by the head. The variation of the magnetic flux produces an induced voltage in the head coil. Therefore, the readback signal can be calculated from Faraday's law. However, the magnetic flux actually going through the head coil is very difficult to calculate directly. Instead of using the cumbersome direct method, a powerful theorem called reciprocity principle, commonly used to calculate the magnetic flux through the head coil, is introduced. Linear superposition of multiple transitions and spectrum analysis of readback signals are also discussed.