Abstract: A method of processing an input broadband signal in RF circuitry includes extracting low-frequency components from the input broadband signal, processing the low-frequency components in low-frequency bypass circuitry, and adding the processed low-frequency components to the output of the RF circuitry to produce a combined output signal. Low-frequency bypass amplifier circuitry for bypassing RF circuitry includes a capacitor having a first terminal for receiving an input signal and a second terminal for connecting to an input of the RF circuitry, and a differential amplifier having two inputs respectively connected to the two terminals of the capacitor, and an output connected to an output of the RF circuitry. High-frequency components of the input signal pass through the capacitor and the RF circuitry, and low-frequency components pass through the differential amplifier and are added to the output of the RF circuitry to produce a combined output signal.

Abstract: A decoder for detecting data within an input signal with attenuated low frequency components that comprises a Viterbi decoder, is disclosed. Viterbi decoder internal data is used along with its output bits to reduce delay between the restored direct current (DC) component and the input signal to zero. As a result, increased accuracy of DC restoration and corresponding bit error rate reduction are achieved.

Abstract: A partial response maximum likelihood (PRML) data detecting in a magnetic recording storage device is carried out with a preliminary measuring of write-read channel responses to all nonzero binary combinations of a given length. Decoding of the user data is performed according to a Viterbi algorithm, where the previously measured responses are used as expected samples for branch metric calculations. The measurement of the write-read channel responses and the decoding of the user data are fulfilled by a self-adjusting PRML receiver that contains a controllable clock recovery, a responses accumulator and an adjustable Viterbi detector. The controllable clock recovery produces a set of read-back signal samples containing exactly one sample per bit with or without phase error correction. The responses accumulator calculates averaged responses of the write-read channel. The adjustable Viterbi detector reconstructs the user data that were written to the disk.

Abstract: A write driver includes two field-effect/bipolar transistors with feedbacks between the drains/collectors and gates/bases, a write/read switch connected between the drains/collectors and a positive power supply, an impedance matching circuit connected to the drains/collectors to match both differential and common mode output impedance of the write driver to an input impedance of a flex circuit, a common mode output voltage control circuit coupled to the transistors, and a differential mode output voltage control circuit coupled to the transistors.

Abstract: An XY platen positioning system includes a fixed base rigidly coupled to a essentially planar surface. An XY intermediate plate is slidably coupled to the fixed base, such that the XY intermediate plate is slidable in the X axis along the fixed base. An XY stage is slidably coupled to the XY intermediate plate, such that the XY stage is slidable in the Y axis along the XY intermediate plate. A platen is flexibly coupled to the XY stage, such that the platen, with respect to the XY stage, is essentially constrained in the X and Y axes and moveable in the Z axis.

Abstract: A spectrum analyzer with a compensation circuitry for prevention of measurement accuracy deterioration due to local oscillators phase noise.

Abstract: A read amplifier system for connection through interconnects to a magnetoresistive (MR) head includes two input transistors, two bias transistors connected to the two input transistors by common source connections, a bias voltage control circuit connected to base terminals of the two bias transistors, a common mode voltage control circuit connected between first and base terminals of the input transistors to provide feedback from the first terminals to the base terminals, and a compensating circuit connected between the outputs of the amplifier system and the base terminals of the input transistors for providing a feedback from the outputs to the base terminals. The two base terminals of the input transistors are respectively connected to the interconnects of the MR head. The bias voltage control circuit applies a bias voltage to base terminals of the two bias transistors, and through the common sources to the base terminals of the input transistors, and thereby across the MR head.

Abstract: A magnetic head and disk tester comprises a base, a spindle for rotationally supporting a magnetic disk, a carriage for supporting a magnetic head support which carries a magnetic head with a magnetic read/write element, and a dual-stage positioning system that moves the carriage in two perpendicular directions X and Y. The magnetic head support, the magnetic head and the magnetic read/write element have a common longitudinal axis Z. The head support is positioned such that the longitudinal axis Z forms a predetermined angle between 0° and 90° with respect to the Y direction. Preferably the predetermined angle is about 45 degrees. When the head is driven from one point of an inner track to a point of an outer track, the displacement of the head along X axis is relatively large and the displacement of the head along Y axis is relatively small.

Abstract: A servo burst pattern for use in positioning a read/write head with respect to tracks on a magnetic disc medium includes a first set of servo bursts adjacently disposed on the tracks along a first axis perpendicular to the centerlines. Each of the first set of bursts is disposed on an individual track, from the inside track edge to the outside track edge, and alternates between a first frequency and a second frequency for consecutive servo bursts. The servo burst pattern also includes a second set of servo bursts adjacently disposed on the tracks along a second axis perpendicular to the centerlines and parallel to the first axis. Each of the second set of servo bursts is disposed on two adjacent tracks, from the centerline of one track to the centerline of a next adjacent track, and alternates between the first frequency and the second frequency for consecutive servo bursts.

Abstract: In a signal acquisition system in accordance with the principles of the present invention, a digital signal acquisition system includes a front end, an equalizer and an output system. The front end typically includes an input amplifier and may include one or more preamplifiers, and any one of various input probes. The probes may be directed toward different applications, that is, voltage probes or current probes, for example, and may include preamplifiers that adjust the range of input signals. The output of the probe is typically routed to an input amplifier, which may include various filters and/other signal conditioning circuitry. The system also includes an analog to digital converter that is arranged to receive a conditioned analog input signal from the input amplifier. The analog to digital converter converts the conditioned analog input signal to digitized input signal.

Abstract: A magnetic medium write precompensation circuit produces a precisely controlled delay for magnetic medium write precompensation by digital-to-analog converting a data value, low-pass filtering the digital-to-analog converted signal, and limiting the filtered signal to produce a desired time delay. One or more of the digital-to-analog conversion levels, limiting levels, and filter cutoff levels determines the amount of the delay. Feedback control may be employed to adjust the digital-to-analog conversion level, filtering, and/or the limiting level to thereby adjust the compensation time delay.

Abstract: In a magnetic recording/reproduction device, such as a disk drive one or more conductive elements is positioned in close proximity to a recording/reproduction head in order to absorb EMI generated by the head as it reads and/or writes data from/to magnetic media. The conductive element is connected through a low impedance path to an electrical sink, such as ground, for absorbed EMI. The conductive element thereby significantly reducing EMI in a manner analogous to the operation of a groundplane in a circuit board. In a disk drive implementation, the conductive element may be positioned on the opposite side of the disk from the head, on the same side of the disk as the head, or one or more conductive elements may be positioned on each side of the disk.

Abstract: A read channel network of a magnetic data storage device receives analog signals representative of user data and servo data, wherein the servo data is usable to position a read/write magnetic head. The servo data is separately processed within the read channel network to improve the signal to noise ratio of the user data signal and, thereby, permit improved positioning accuracy of the read/write head within the magnetic data storage device. The servo signal applied to a multiplier along with an oscillating signal reference signal to produce a sideband signal, which is passed through a bandpass filter having a bandwidth about that of the sideband signal and having a center frequency substantially the same as that of the sideband signal. Additionally, the signal output by the bandpass filter is processed by an envelope detector, and then by an A/D converter and digital filter to produce a digital signal representative of the servo signal.

Abstract: A magnetic head and disk tester includes a magnetic head which is selectively positioned relative to a rotatably mounted magnetic disk to accomplish testing of either of the head or disk or both. The magnetic head is secured to a carriage which is under electro-mechanical control, wherein displacement of the carriage causes a corresponding displacement of the head relative to the disk and, to some degree, may cause yaw in the carriage. Measurements of the linear position of a left and a right side of the carriage are detected, measured, and fed back to a control system. The control system responds to a difference between a desired command position and the actual position of each side of the carriage and causes actuators to adjust the position of each side of the carriage until the difference, and thereby the yaw, is substantially eliminated. Additionally, during a positioning operation, vibrations in the yaw direction are decreased, which decreases a corresponding settling time of the magnetic head.

Abstract: A magnetic head and disk tester provides accurate positioning of a magnetic read-write head over a magnetic disk by means of a coarse positioning mechanism and a fine positioning mechanism. The coarse positioning mechanism includes a stepper motor, a lead screw, a nut, rear sliders and a housing. The fine positioning mechanism includes a piezoelectric actuator, slides and a carriage. The positioning displacements are along a linear axis, which lies on a horizontal plane. The carriage is connected to the housing via the fine positioning mechanism, which then moves the carriage with respect to the housing. Two pairs of linear encoders are mounted on the carriage about the axis and measure the position of the magnetic read-write head with respect to the magnetic disk. Each pair is mounted such that the pairs lie in separate horizontal planes.

Abstract: A shroud of suitable shape is provided about the spindle and disk(s) of a spinstand. In some forms, a shell is disposed between the disk locus and the shroud. The shroud (and/or shell) operates to reduce or eliminate air flow at the top and bottom surfaces of the disk(s) and limits the air volume moved by the rotating disk(s). The shroud (and/or shell) also directs the air in a circular path around the spindle center. As a result, vortexes in the air surrounding the disks are significantly reduced, thereby decreasing the vibrations of the disk(s) and the heads and decreasing track misregistration. The shroud (and/or shell) also reduces the heat exchange between the ambient air and the magnetic disk(s), which in turn reduces the thermal expansion of the disk(s) and thus decreases the track misregistration further. The shroud (and/or shell) also provides electromagnetic shielding for the disk(s) and head(s) installed on the spinstand and thus increases the quality of the signal read from the magnetic disk(s).

Abstract: A shroud of suitable shape is provided about the spindle and disk(s) of a spinstand. The shroud operates to reduce or eliminate air flow at the top and bottom surfaces of the disk(s) and limits the air volume moved by the rotating disk(s). The shroud also directs the air in a circular path around the spindle center. As a result, vortexes in the air surrounding the disks are significantly reduced, thereby decreasing the vibrations of the disk(s) and the heads and decreasing track misregistration. The shroud also reduces the heat exchange between the ambient air and the magnetic disk(s), which in turn reduces the thermal expansion of the disk(s) and thus decreases the track misregistration further. The shroud also provides electromagnetic shielding for the disk(s) and head(s) installed on the spinstand and thus increases the quality of the signal read from the magnetic disk(s).

Abstract: An apparatus for substantially eliminating a switching voltage transient in a magnetic recording system so as to minimize a write-to-read recovery time includes a first bias enable switch, a bias current source responsive to the first bias enable switch, an MR sensor for receiving a bias current from the current source, and a read amplifier being capacitively coupled to the MR sensor. The bias current flowing through the MR sensor produces the switching voltage transient due to the RC time constant presented by the input of the read amplifier. The apparatus includes a first compensating circuit for generating a compensating voltage transient having a polarity substantially equal and opposite to the switching transient. The first compensating circuit is electrically coupled to the MR sensor, and a superposition of the switching voltage transient and the compensating voltage transient is substantially zero.

Abstract: A radially distributed transverse filter includes a plurality of delay lines of substantially equal electric length sequentially coupled at a like plurality of nodes. The nodes are distributed equidistant from a common position, for example positioned at vertices of a polygon. A plurality of attenuators are distributed radially about the common position and coupled between the nodes and the common position. An adder is located substantially at the common position for summing the attenuator outputs. In this manner, the respective propagation delays of each tap are substantially similar, and imprecision due to variation in propagation delay is therefore mitigated and/or substantially eliminated. The invention has application to high-frequency digital and analog transverse filters, for example filters for equalizers used in Partial Response Maximum Likelihood (PRML) circuits employed in contemporary magnetic recording systems.

Abstract: A spinstand head-loading mechanism of a magnetic tester includes a protector bar and a lift arm which control the loading and unloading operations of a magnetic head, as part of a head-gimbal assembly, with respect to a magnetic disk. A series of actuators control the engagement and disengagement of protector bar and lift arm with a head-gimbal assembly that includes read/write elements as part of a slider. The protector bar is driven in a Y-axis direction by an actuator, while the head-gimbal assembly is disposed in an X-axis direction, orthogonally to the Y-axis. The lift arm is also driven in the Y-axis direction by an actuator, but is also driven in a Z-axis direction by a different actuator. Before testing, the head of the head-gimbal assembly is loaded onto a magnetic disk. To accomplish this, the head-gimbal assembly is initially installed on the head-loading mechanism.