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Abstract
Understanding of medium noise is crucial for developing high-density tape recording systems. In this dissertation, various types of medium noise are studied both experimentally and theoretically. Measurement techniques and analyzing methods are developed for each phenomenon.
The experimental studies of the head/tape spacing are presented in Chapter 3. A new method using magnetic measurement is introduced. The magnetic results agree well with mechanical analysis using FEM simulation validated by interferometric measurements. Tape medium noise due to clusters and packing fluctuations is studied in chapter 4. The fundamental bulk AC and DC erases tape medium noise is measured and analyzed. A particle clustering model is utilized to fit the measured spectra. The cluster distribution function and the particle cluster diameters are determined. Medium noise due to surface roughness during playback process is studied in chapter 5. The results of from both mechanical and magnetic methods are present. Tape surface roughness correlation length l and roughness variance σ were characterized. The broad band signal dependent noise is studied in Chapter 6. Both time domain and spectral domain methods are utilized to characterize the signal dependent noise. In Chapter 8 the PRML channel performance under the influence of medium noise is examined via the numerical simulations. A modified self-consistent model, which incorporates a log normal particle size distribution and a random packing of the particles, is utilized to simulate the recording process. A pre-developed error rate model is utilized to evaluate the system performance with fixed head/medium combinations. Surface roughness is introduced as a varying random head/tape spacing during both the recording and the playback processes. The impact of mean particle length, roughness variance and roughness correlation length on system performance is examined for a partial response (PR4) channel.
