Method and apparatus for the coherent demodulation of an amplified modulated carrier using a dual track and hold amplifier and the application of said method and apparatus to measurement of magnetic media performance
US5699204A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 8, 1995 |
| Grant date | Dec 16, 1997 |
| Priority date | — |
| Expiry date | Nov 8, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B33/10
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
An apparatus and method for demodulating an amplitude modulated read signal generated by a magnetic head of a hard disk drive. The apparatus includes a pair of serially connected track and hold circuits that receive the read signal. The track or hold state of each circuit is controlled by a phase lock loop circuit which also receives the read signal. The first track and hold circuit initially tracks the read signal to a peak value. The circuit then switches to a hold state and provides a constant output signal that corresponds to the peak voltage of the read signal. While the first track and hold circuit is in the hold state, the second track and hold circuit is in a tracking state. The second track and hold circuit tracks the output of the first circuit. Because the output of the first circuit is a constant value, the second circuit also provides a constant output signal in the tracking state. The first circuit is switched back to the tracking state to again track the amplitude of the read signal, and the second circuit is switched to the hold state. The process is repeated to create a "stepped" demodulated signal. The output signals are compared to a threshold value to detect bit…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.