摘要:
A multi-mode timing loop for a PR4,ML sampled data channel includes an analog to digital converter and a digital finite impulse response filter for providing conditioned digital samples. The timing loop includes a reference clock source for putting out a reference clock frequency related to a nominal sample data rate, a frequency controllable oscillator connected to generate a sample clock, an analog timing loop and a digital timing loop. The analog timing loop provides phase lock during non-data read mode, and during data read mode the digital timing loop provides a vernier offset for fine adjustment of phase lock to a static setting then provided by the analog timing loop.
摘要:
A class IV partial response, maximum likelihood data channel for a disk drive includes an encoder connected to a data sequencer for converting user data blocks into a predetermined 8/9ths code such as a (0,4,4,) code. A precoder conveys the 8/9ths code into class IV code. An analog write driver supplies the class IV code to a data transducer head during data write-to-disk operations. A read channel connected to the head amplifies and conditions analog signals during data read operations. A quantizer produces samples of the analog signals in accordance with a quantization clock generated by a clock generator. An adaptive FIR filter means is conditions the data samples in accordance with selectable, adaptive filter coefficients. A Viterbi detector puts out the class IV code from the filtered and quantized samples. A postcoder conveys the detected class IV code into detected 8/9ths code. A decoder converts the detected 8/9ths code into user data and supplies user data to the sequencer. The programmable FIR filter is provided with servo coefficients during reading of the servo sectors, and an asynchronous servo detector detects head position information from the quantized and filtered samples without phase locking of the quantization clock generator to the quantized servo samples. The asynchronous servo detector is also used to aid detection of sync field preamble information before the FIR filter is fully adapted. Multi-mode gain and timing loops are also a part of the present invention.
摘要:
A class IV partial response, maximum likelihood data channel for a disk drive includes an encoder connected to a data sequencer for converting user data blocks into a predetermined 8/9ths code such as a (0,4,4,) code. A precoder converts the 8/9ths code into class IV code. An analog write driver supplies the class IV code to a data transducer head during data write-to-disk operations. A read channel connected to the head amplifies and conditions analog signals during data read operations. A quantizer produces samples of the analog signals in accordance with a quantization clock generated by a clock generator. An adaptive FIR filter means is conditions the data samples in accordance with selectable, adaptive filter coefficients. A Viterbi detector puts out the class IV code from the filtered and quantized samples. A postcoder converts the detected class IV code into detected 8/9ths code. A decoder converts the detected 8/9ths code into user data and supplies user data to the sequencer. The programmable FIR filter is provided with servo coefficients during reading of the servo sectors, and an asynchronous servo detector detects head position information from the quantized and filtered samples without phase locking of the quantization clock generator to the quantized servo samples. The asynchronous servo detector is also used to aid detection of sync field preamble information before the FIR filter is fully adapted. Multi-mode gain and timing loops are also a part of the present invention.
摘要:
A class IV partial response, maximum likelihood data channel for a disk drive includes an encoder connected to a data sequencer for converting user data blocks into a predetermined 8/9ths code such as a (0,4,4,) code. A precoder converts the 8/9ths code into class IV code. An analog write driver supplies the class IV code to a data transducer head during data write-to-disk operations. A read channel connected to the head amplifies and conditions analog signals during data read operations. A quantizer produces samples of the analog signals in accordance with a quantization clock generated by a clock generator. An adaptive FIR filter means is conditions the data samples in accordance with selectable, adaptive filter coefficients. A Viterbi detector puts out the class IV code from the filtered and quantized samples. A postcoder converts the detected class IV code into detected 8/9ths code. A decoder converts the detected 8/9ths code into user data and supplies user data to the sequencer. The programmable FIR filter is provided with servo coefficients during reading of the servo sectors, and an asynchronous servo detector detects head position information from the quantized and filtered samples without phase locking of the quantization clock generator to the quantized servo samples. The asynchronous servo detector is also used to aid detection of sync field preamble information before the FIR filter is fully adapted. Multi-mode gain and timing loops are also a part of the present invention.
摘要:
A multi-mode gain control loop for a PR4, ML data channel, such as one included in a magnetic disk data storage device, includes an input for receiving from a source an analog signal stream including coded data to be detected; a VGA for amplifying the analog signal stream; an analog to digital converter for receiving the analog signal stream and for generating and putting out data samples therefrom; an analog gain control loop connected to generate an analog gain control from the analog data stream during a data non-read mode of the channel, to store the analog gain control in a storage circuit, and to apply the stored analog gain control constantly to control the VGA; and a digital gain control loop connected to generate gain vernier correction values from the data samples and for applying the gain vernier correction values through a gain DAC to provide an offset control to the VGA during a data read mode of the channel.
摘要:
A digital adaptive finite impulse response filter circuit is provided for a PR4,ML sampled data channel including an analog to digital sampler for providing raw digital samples of data to the filter circuit and a sampled data detector for detecting coded data from conditioned digital samples received from the filter circuit. The filter circuit comprises a multi-tap transversal filter structure wherein each tap is connected to receive a selected coefficient, a source of a plurality of coefficients for each tap, a coefficient selector connected to the source to receive the plurality of coefficients and to provide a selected coefficient to each tap of the transversal filter structure, and a control circuit for controlling the coefficient selector and the source for providing each of the selected coefficients to a corresponding tap of the transversal filter structure. Training and adaptation methods and circuits for adapting the filter structure are also described.
摘要:
A digital peak detection circuit asynchronously detects embedded overhead information such as servo or sync pattern data within a PR4,ML synchronous data detection channel of a magnetic disk drive. The channel includes an analog to digital converter clocked by a data clock operating asynchronously with respect to playback of the embedded overhead information in the channel for converting an analog data stream into raw data samples, and an adaptive digital FIR filter for conditioning the raw data samples into conditioned data samples in accordance with programmable filter coefficients. The digital peak detection circuit includes a filter adaptation circuit for programming the digital FIR filter to a bandwidth characteristic selected for the embedded overhead information, a plurality of tapped clock delays each connected in tandem to receive and progressively by a period related to said data clock to delay conditioned data samples of the embedded overhead information, a first comparison logic array connected to predetermined taps of said tapped data clock period delays for comparing said conditioned data samples of the embedded overhead information at said taps and for generating a first logical condition therefrom, a second comparison logic array connected to a predetermined tap of said tapped clock delay means and to a threshold-providing circuit, for comparing the conditioned data samples of the embedded overhead information at the taps with threshold values provided by the threshold-providing circuit and for generating a second logical condition therefrom, and a digital combining circuit for combining the first logical condition and the second logical condition in order to detect and put out the embedded overhead information. A fault tolerant sync pattern detection method and apparatus is also disclosed.
摘要:
An adaptive filter for use in disk drive systems includes coefficient adaptation circuitry operating at a slower rate than the filter and consequently at a reduced power level. The adaptive filter receives input data samples corresponding to raw data read from a disk in the disk drive system and converted to digital form and provides processed output data samples. The action of the filter is defined by characteristic filter coefficients having values that are updated by adaptation circuitry during the operation of the filter. The adaptive filter is independently clocked from the adaptation circuitry, such that the input data samples and the processed output data samples are clocked through the adaptive filter at a clock rate 1/T, and the filter coefficients are updated according to a prescribed algorithm at an update rate slower than the 1/T clock rate. Filter coefficient updating occurs preferably at a rate equal to 1/J, where J is an integer greater than unity and generally in the range of 2 to 8. The coefficient update rate is achieved by providing a separate filter coefficient adaptation clock derived from the system clock by dividing that clock by a user-programmable parameter J. This process reduces the coefficient update rate, which in turn reduces the switching frequency of the logic gates, the number of pipeline latches, and, ultimately, the power consumption.
摘要:
An ultra-wideband clear channel assessment system uses a double-window energy technique for energy detection, which indicates a clear or busy channel.
摘要:
A method in which several high voltage chips may be packaged within a single, typically low voltage plastic package. The high voltage chips are packaged to remain electrically isolated from each other to avoid undesirable side effects such as arcing between the chips but able to share electronic data and communicate with each other electronically through their input and ouput nodes. Due to the unique packaging method, the typically low voltage plastic packaging can be made to withstand operating voltages up to 35 times greater than previously attained by such low voltage plastic packaging.