Acorn Technologies, Inc.

Purchased Patent Management LLC

Alvin M Despain

R Stockton Gaines

Petros A Ioannou

Elias B Kosmatopoulos

Multistage Wiener filters (MWF) represent a component of the MWF as an un-normalized vector of filter coefficients within a finite impulse response (FIR) filter in a manner that avoids reliance on the 2-norm operation of the un-normalized vector of coefficients. The 2-norm operation can be replaced by less expensive operations performed elsewhere in the MWF. Preferably the filter adds only a few additional addition, subtraction and multiplication operations to compensate for the elimination of the square root and the division operations used for the 2-norm operation. As a result, it is possible to eliminate all or nearly all of the square rod and arithmetic division operations of at least some implementations of the MWF.

Reduced complexity adaptive multistage wiener filter

A CDMA radio system uses an adaptive filter in a receiver to mitigate multipath radio propagation and to filter out interfering signals. Characteristics of an initial stage of the filter preferably are determined by cross correlation of a generated pilot signal and the input signal with the integration of the correlation performed over a time period selected to be an integral number of symbol periods. The integration causes the portions of the cross correlation corresponding to the user subchannels to average substantially to zero, so that the pilot channel signal correlation is the primary contribution to the signal used to characterize the channel to establish the coefficients of the adaptive filter for the receiver.

Efficient adaptive filters for CDMA wireless systems

A code division multiple access (CDMA) radio system uses an adaptive filter in a receiver to mitigate multipath radio propagation and to filter out interfering signals. Characteristics of an initial stage of the filter preferably are determined by cross correlation of a generated pilot signal and the input signal with the integration of the correlation performed over a time period selected to be an integral number of symbol periods. The integration causes the portions of the cross correlation corresponding to the user subchannels to average substantially to zero, so that the pilot channel signal correlation is the primary contribution to the signal used to characterize the channel to establish the coefficients of the adaptive filter for the receiver.

Use of adaptive filters in multiple access wireless systems employing predictable signals

A servo control apparatus and method controls systems at least partially on the basis of an observable variable that has an absolute value functional relationship with the controlled variable and does not change sign for positive and negative variations from a nominal value. When applied to the positional control of an object, the control system observes a value of a position error signal and maps that signal to two different potentially correct displacement values. Two estimators within the control system are initiated, one using the positive displacement and the other using the negative displacement, and the two estimators each predict the future position of the object and the corresponding position error signal for each estimated position. A new position error signal is detected and compared to the two estimated position error signals. After sufficient system evolution, the control system can select one or the other of the estimators as being correct and the associated displacement is identified as correct and is used for future positioning applications, preferably until the sign of the displacement of the head again becomes ambiguous. The control system can be used in combination with other control mechanisms including those using complimentary control information that provides more complete positioning information. The control method, system and apparatus find particularly advantageous application in magnetic storage hard disk drive systems.

Servo control appartaus and method using absolute value input signals

Apparatus using information about the extent of errors in sensed data for performing as a control function at least one of adjusting the position of a magnetic head to improve alignment relative to a track and selecting from two or more data signals a data signal having the least amount of errors is shown. The apparatus uses information about the extent of errors to perform a control function for reproducing the data stored in predetermined storage locations in a storage media. The apparatus positions a transducer for sensing from predetermined storage locations stored data containing at least one constraint. The transducer generates a first signal representative of the data containing at least one constraint stored in the sensed data and any errors introduced into the sensed data during the sensing. An input device, preferably in the form of a detector is responsive to the first signal for generating a control signal containing information about the extent of errors in the sensed data and for extracting a data signal. The control signal is used for performing the above control functions. A method for using information about the extent of errors for a control function to improve the extracted data stored at the predetermined storage locations is also shown.

Method and apparatus for developing a dynamic servo signal from data

A computationally efficient, adaptive multistage Wiener filter employs two modules, a linear filter module that operates at the input data rate and an update module that operates at a plurality of rates but performs many calculations at only the update rate. This filter is especially useful when the channel conditions vary slowly so that the filter's update rate can be considerably less than the input data rate. Separating the calculations, preferably performing appropriate calculations at different rates and preferably substituting scalar operations for vector operations can provide improved computational efficiency while maintaining high levels of performance.

Adaptive multistage wiener filter

A servo control system and method controls systems at least partially on the basis of an observable variable that has an absolute value functional relationship with the controlled variable and does not change sign for positive and negative variations from a nominal value. The control system and method find particularly advantageous application in magnetic storage hard disk drive systems because the system allows such hard disk drives to perform servo operations such as track following on the basis of the data signals being read from the track. A particularly useful source of the absolute value observable variable is a read channel chip that performs decoding of data recovered from the disk. Error measures are developed as the data signals from the disk are processed and decoded, including error measures from the slicer used in an adaptive equalization process and from the data decoder, which may be a Viterbi decoder. One or more of these error measures is provided to an output terminal of the read channel chip for use with an absolute value control system and method.

Read channel generating absolute value servo signal

Servo control apparatus and method using absolute value input signals

Apparatus for developing a dynamic servo signal from data in a magnetic disc drive and method

A device using information about the extent of errors in a signal is shown. The device includes an input signal containing at least one constraint and any errors introduced into the input signal during transmission and/or sensing. A detector receives and is responsive to the input signal for generating an error signal containing information about the extent of error and for extracting an information signal from the input signal as an output signal. A control device is operatively coupled to the detector for receiving and responding to the error signal containing information about the extent of errors for generating a control signal used to reduce the extent of errors in the input signal based on information about the extent of errors contained in the error signal. A method for using information about the extent of errors is shown.

Device for using information about the extent of errors in a signal and method

The invention is a method and apparatus for (1) enhancing the transmission of information in a particular direction or (2) enhancing the reception of information from a particular direction by an array of transducers, a transducer being any device for transforming radiated power into electrical power and vice versa. A transducer signal is associated with each transducer in an array, the plurality of transducer signals being the vehicle for transmitting or receiving information. Each transducer signal is the sum of a first product and a second product. The first product is the product of a first signal and a cosine function of an argument. The second product is the product of a second signal and a sine function of the same argument. An argument is the sum of a phase and a product of an angular frequency and time. The bandwidths of the first and second signals are less than half a reference frequency W, and the angular frequency of the sine and cosine functions is greater than 2&pgr; times the reference frequency. The method comprises the steps of (1) adjusting the arguments of the sine and cosine functions and (2) adjusting an embedded time reference in the first and second signals with respect to a real-time reference.

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Alvin M Despain