# US 7,206,154 B2 · Method and apparatus for balanced shield shunts, leads and pads for electrical noise reduction in read heads > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,206,154 B2 - Document ID: US7206154B2 - Status: Granted - Kind: B2 - Application number: 10/254,285 - Filed: 2002-09-25 - Published: 2004-03-25 - Granted: 2007-04-17 - Earliest claimed: 2002-09-25 - Assignees: Hitachi Global Storage Technologies Netherlands B.V. - Inventors: Edward Hin Pong Lee; Robert Langland Smith - Web page: https://patentgrep.com/patent/US7206154B2 ## CPC - G11B 5/3903: {using magnetic thin film layers or their effects, the films being part of integrated structures} - G11B 5/00: Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor (G11B11/00 {and G11B13/00} take precedence) - G11B 5/012: Recording on, or reproducing or erasing from, magnetic disks (G11B17/00, G11B19/00 take precedence) - G11B 5/40: Protective measures on heads, e.g. against excessive temperature (G11B5/31 takes precedence; protection against wear G11B5/255 {; protective structure of the head: see under structures, e.g. G11B5/3106}) - G11B 20/10009: {Improvement or modification of read or write signals} - G11B 20/1403: {characterised by the use of two levels} - G11B 5/11: Shielding of head against electric or magnetic fields - G11B 23/0007: {Circuits or methods for reducing noise, for correction of distortion, or for changing density of recorded information, (volume compression or expansion circuits per se H03G7/00)} - G11B 2005/0016: {of magnetoresistive transducers} - G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R) ## Abstract A symmetrical read element circuit for reducing electrical and magnetic noise using signal processing, such as a differential preamplifier. The circuits are symmetrically created on both sides of the read element so that the noise is balanced on both leads of the sensor element allowing substantial noise reduction by the signal processing. That is, the present invention provides symmetrical leads and pads designed for equal noise pickup, and for cancellation of the balanced noise. ## Claims ### Claim 1 A method for reducing noise in a differential output signal of a magnetic head, comprising: providing a sensor element within a magnetic head for detecting a magnetically recorded signal and producing a differential read signal in response thereto; providing within the magnetic head a first sensor element signal path having a first physical structure selected to provide first electrical characteristics including a first noise signal component of the read signal on the first sensor element signal path at a first head output terminal; and providing within the magnetic head a second sensor element signal path having a second physical structure selected to provide second electrical characteristics including a second noise signal component of the read signal on the second sensor element signal path at a second head output terminal; and wherein design characteristics of the first and second physical structures are selected to be symmetrical for equalizing the first and second electrical characteristics thereby allowing the output signal of the magnetic head from the first and second physical structures to be differentially processed to cancel the first noise signal component with the second noise signal component. ### Claim 2 (depends on 1) The method of claim 1 further comprising processing the balanced first and second noise signal components to eliminate the first and second noise signal components. ### Claim 3 (depends on 1) The method of claim 1 further comprising providing a differential amplifier wherein the first and second noise signal components are cancelled by the differential amplifier. ### Claim 4 (depends on 3) The method of claim 3, wherein the processing the first and second noise signal components further comprises differentially preamplifying signals from the first and second sensor signal paths to eliminate the first and second noise signal components thereof. ### Claim 5 (depends on 1) The method of claim 1, wherein the providing a first sensor element signal path within the magnetic head further comprising providing a first lead and a first pad and wherein the providing a second sensor element signal path within the magnetic head further comprises providing a second lead and a second pad, wherein design characteristics of the first pad is symmetrical with design characteristics of the second pad and design characteristics of the the first lead is symmetrical with design characteristics of the second lead. ### Claim 6 (depends on 5) The method of claim 5, wherein the providing a first lead and a first pad and the providing a second lead and a second pad further comprises creating symmetrical capacitances, resistances and inductances in the first and second pads. ### Claim 7 (depends on 1) The method of claim 1 further comprising providing a first shield shunt and a second shield shunt, wherein the design characteristics of the first shield shunt is symmetrical with the design characteristics of the second shield shunt. ### Claim 8 (depends on 1) The method of claim 1, wherein the providing a first and second noise signal components further comprises providing noise generated from at least a substrate, a shield, and a disk, wherein the first and second sensor element signal paths are formed so that the noise generated from at least the substrate, the shield, and the disk for the first and second sensor element signal paths are balanced. ### Claim 9 A read channel, comprising: a sensor element disposed within a magnetic head for detecting a magnetically recorded signal and producing a differential read signal in response thereto; a first sensor element signal path formed within the magnetic head, the first sensor element signal path having a first physical structure selected to provide first electrical characteristics including a first noise signal component of the read signal on the first sensor element signal path at a first head output terminal; and a second sensor element signal path formed within the magnetic head, the second sensor element signal path having a second physical structure selected to provide second electrical characteristics including a second noise signal component of the read signal on the second sensor element signal path at a second head output terminal; wherein design characteristics of the first and second physical structures are selected to be symmetrical for equalizing the first and second electrical characteristics thereby allowing the output signal of the magnetic head from the first and second physical structures to be differentially processed to cancel the first noise signal component with the second noise signal component. ### Claim 10 (depends on 9) The read channel of claim 9 further comprising a signal processor for processing the balanced first and second noise signal components to eliminate the first and second noise contributions. ### Claim 11 (depends on 10) The read channel of claim 10, wherein the signal processor further comprises a differential amplifier wherein the first and second noise signal components are cancelled by the differential amplifier. ### Claim 12 (depends on 10) The read channel of claim 10, wherein the signal processor differentially preamplifies signals from the first and second sensor signal paths to eliminate the first and second noise signal components thereof. ### Claim 13 (depends on 9) The read channel of claim 9, wherein the first sensor element signal path within the magnetic head further comprising a first lead and a first pad and wherein the second sensor element signal path within the magnetic head further comprises a second lead and a second pad, wherein design characteristics of the first pad is symmetrical with design characteristics of the second pad and design characteristics of the the first lead is symmetrical with design characteristics of the second lead. ### Claim 14 (depends on 13) The read channel of claim 13, wherein the first pad and the second pad provide symmetrical capacitances, resistances and inductances. ### Claim 15 (depends on 9) The read channel of claim 9 further comprising a first shield shunt and a second shield shunt, wherein the design characteristics of the first shield shunt is symmetrical with the design characteristics of the second shield shunt. ### Claim 16 (depends on 15) The read channel of claim 15, wherein the noise generated from at least the substrate, the shield, and the disk for the first and second sensor element signal paths are balanced. ### Claim 17 A magnetic storage device, comprising magnetic media for storing data thereon; a motor for translating the position of the magnetic media; and an actuator for positioning a magnetic head for reading signals from the magnetic media, the magnetic head comprising: a sensor element disposed within a magnetic head for detecting a magnetically recorded signal and producing a differential read signal in response thereto; a first sensor element signal path formed within the magnetic head, the first sensor element signal path having a first physical structure selected to provide first electrical characteristics including a first noise signal component of the read signal on the first sensor element signal path at a first head output terminal; and a second sensor element signal path formed within the magnetic head, the second sensor element signal path having a second physical structure selected to provide second electrical characteristics including a second noise signal component of the read signal on the second sensor element signal path at a second head output terminal; wherein design characteristics of the first and second physical structures are selected to be symmetrical for equalizing the first and second electrical characteristics thereby allowing the output signal of the magnetic head from the first and second physical structures to be differentially processed to cancel the first noise signal component with the second noise signal component. ### Claim 18 (depends on 17) The magnetic storage device of claim 17 further comprising a signal processor for processing the balanced first and second noise signal componets to eliminate the first and second noise signal componets. ### Claim 19 (depends on 18) The magnetic storage device of claim 18, wherein the signal processor further comprises a differential amplifier wherein the first and second noise signal components are cancelled by the differential amplifier. ### Claim 20 (depends on 18) The magnetic storage device of claim 18, wherein the signal processor differentially preamplifies signals from the first and second sensor signal paths to eliminate the first and second noise signal componets thereof. ### Claim 21 (depends on 17) The magnetic storage device of claim 17, wherein the first sensor element signal path within the magnetic head further comprising a first lead and a first pad and wherein the second sensor element signal path within the magnetic head further comprises a second lead and a second pad, wherein design characteristics of the first pad is symmetrical with design characteristics of the second pad and design characteristics of the the first lead is symmetrical with design characteristics of the second lead. ### Claim 22 (depends on 21) The magnetic storage device of claim 21, wherein the first pad and the second pad provide symmetrical capacitances, resistances and inductances. ### Claim 23 (depends on 17) The magnetic storage device of claim 17 further comprising a first shield shunt and a second shield shunt, wherein the design characteristics of the first shield shunt is symmetrical with the design characteristics of the second shield shunt. ### Claim 24 (depends on 23) The magnetic storage device of claim 23, wherein the noise generated from at least the substrate, the shield, and the disk for the first and second sensor element signal paths are balanced. ### Claim 25 A read channel, comprising: means disposed within a magnetic head for detecting a magnetically recorded signal and producing a differential read signal in response thereto; first means formed within the means for detecting, for providing a first physical structure selected to provide first electrical characteristics including a first noise signal component of the read signal on the first sensor element signal path at a first head output terminal; and second means formed within the means for detecting, for providing a second physical structure selected to provide second electrical characteristics including a second noise signal component of the read signal on the second sensor element signal path at a second head output terminal; wherein design characteristics of the first and second means for providing physical structures are selected to be symmetrical for equalizing the first and second electrical characteristics thereby allowing the output signal of the means for detecting from the first and second means for providing physical structures to be differentially processed to cancel the first noise signal component with the second noise signal component.