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Trigonal Buried Servo Encodement for Single Frequency Derivation of Position Error Signal

IP.com Disclosure Number: IPCOM000047457D
Original Publication Date: 1983-Nov-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Jove, SA: AUTHOR

Abstract

This article outlines a method of obtaining a constant phase servo reference signal from multi-phased servo tracks, and a method of generating a resultant position error signal (PES). Moreover, since the servo tracks are of the same frequency, minimal degradation to data residing above the servo results (Fig. 3a). It is proposed that a buried servo system use single frequency servo tracks of the phase orientation shown in Fig. 1, hereafter referred to as trigonal orientation. Two servo elements are needed: a servo data element (H1), and a servo reference element (H2). The rotating vector P1 in the vector diagram of Fig. 1 represents the output of the servo data element as it moves across tracks from position 1 to position 6. The servo reference element (P2) width is equal to three trackwidths.

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Trigonal Buried Servo Encodement for Single Frequency Derivation of Position Error Signal

This article outlines a method of obtaining a constant phase servo reference signal from multi-phased servo tracks, and a method of generating a resultant position error signal (PES). Moreover, since the servo tracks are of the same frequency, minimal degradation to data residing above the servo results (Fig. 3a). It is proposed that a buried servo system use single frequency servo tracks of the phase orientation shown in Fig. 1, hereafter referred to as trigonal orientation. Two servo elements are needed: a servo data element (H1), and a servo reference element (H2). The rotating vector P1 in the vector diagram of Fig. 1 represents the output of the servo data element as it moves across tracks from position 1 to position 6. The servo reference element (P2) width is equal to three trackwidths.

This geometry exploits the asymmetric phase orientation by cancelling the 0OE and 180OE track readback independent of H2 position. As the servo reference element moves from position 1 to position 6, a constant phase output at 90OE results. This is shown as P2 on the vector diagram. A phase-locked loop (PLL) is used to lock onto the reference phase. Additional references are then generated at P2 + 90OE, P2 - 45OE and P2 - 135OE. This is shown in the functional block diagram of Fig. 2. When these references are multiplied with P1 data and lowpass filtered, PES information becomes availab...