Compensation of PLL Loop Delay in Read Channels for Tape Storage Systems

This paper studies loop-delay compensation as a means to improve the robustness of timing recovery loops in tape storage systems. The delay compensation scheme is derived under fairly general assumptions and is found to match a known Kalman-filtering-based solution if a random-walk model of frequency-offset evolution is assumed. Extensions of the scheme to achieve delay compensation in multichannel tape-drive systems that employ global timing control are presented. The practical effectiveness of delay compensation is demonstrated using actual readback waveforms captured on commercial tape drives.