Systems and methods for adaptive baseline compensation
Various embodiments of the present invention provide systems and methods for reducing low frequency loss in a magnetic storage device. For example, some embodiments provide data processing circuits that include: an input circuit, a processing circuit, a data detection circuit, and a baseline compensation circuit. The input circuit receives a first data input and provides a second data input. The input circuit excludes low frequency energy exhibited in the first data input from the second data input. The processing circuit generates a representation of the second data input, and the data detection circuit generates a representation of the first data input based at least in part on the representation of the second data input. The baseline compensation circuit calculates an accumulated difference between the representation of the first data input and the representation of the second data input across a number of bit periods, and calculates a compensation factor based at least in part on the accumulated difference.
1. A data processing system, the system comprising:
a preamplifier operable to receive an input signal derived from a storage medium, and amplify the input signal to generate an amplified signal;
an analog to digital converter operable to convert the amplified signal to a corresponding digital signal;
a data detector operable to provide a detected data output based at least in part on a detector input derived from the digital signal, and wherein the detected data output represents the input signal;
a baseline compensation module, wherein the baseline compensation module includes:
an accumulator circuit operable to accumulate a difference between the detector input and the detected data output, and
a calculation circuit operable to calculate a compensation factor based on the accumulated difference; and
a summation element operable to aggregate the compensation factor with the amplified signal.
2. The system of claim 1 , wherein the digital signal is filtered using a digital finite impulse response filter to yield the detector input.
3. The system of claim 1 , wherein the accumulated difference is accumulated by dividing the difference for each respective bit period by the detected data output for the respective bit period to yield a product of the division, and adding the product of the division across a number of bit periods.
4. The system of claim 3 , wherein the number of bit periods corresponds to the number of bit periods of a sector of the storage medium.
5. The system of claim 1 , wherein the baseline compensation module includes a variable q low pass filter.
6. The system of claim 1 , wherein the accumulated difference is accumulated by multiplying the difference for each respective bit period by the sign of the detected data output for the respective bit period to yield a product of the multiplication, and adding the product of the multiplication across a number of bit periods.
7. The system of claim 6 , wherein the accumulated difference does not include the product of the multiplication where the magnitude of the detected data output is less than a threshold value for a respective bit period.
8. The system of claim 1 , wherein the baseline compensation module includes a digital to analog converter.
9. A method for performing a baseline compensation, the method comprising:
receiving a first analog input signal, wherein the first analog input signal corresponds to a second analog input signal that has been high pass filtered;
converting the first analog input signal to a digital signal;
performing a data detection on the digital signal to provide a detected data output;
calculating a difference between the digital signal and the detected data output;
aggregating the difference with an accumulated difference to create a difference accumulation; and
modifying a pole of a low pass filter using the difference accumulation.
10. The method of claim 9 , wherein the method further comprises:
aggregating an output derived from the low pass filter with the first analog input, wherein low frequency energy removed from the first analog input is restored.
11. The method of claim 9 , wherein the difference is calculated by subtracting the digital signal from the detected data output and dividing the result by the detected data output.
12. The method of claim 9 , wherein the difference is calculated by subtracting the digital signal from the detected data output and multiplying the result by the sign detected data output.
13. The method of claim 9 , wherein the difference is calculated by subtracting the digital signal from the detected data output and multiplying the result by the sign detected data output for bit periods where the magnitude of the detected data output exceeds a threshold.
14. The method of claim 9 , wherein the difference accumulation is multiplied by a damping factor to create a damped difference factor, and modifying the pole of the low pass filter is done using the damped difference factor.
15. A data processing circuit, wherein the circuit comprises:
an input circuit operable to receive a first data input and provide a second data input, wherein the input circuit excludes low frequency energy exhibited in the first data input from the second data input;
a processing circuit operable to generate a representation of the second data input;
a data detection circuit operable to generate a representation of the first data input based at least in part on the representation of the second data input; and
a baseline compensation circuit including:
an accumulator circuit operable to calculate an accumulated difference between the representation of the first data input and the representation of the second data input across a number of bit periods, and
a calculation circuit operable to calculate a compensation factor based at least in part on the accumulated difference.
16. The circuit of claim 15 , wherein the input circuit is a preamplifier, and wherein the first data input is derived from a magnetic storage medium.
17. The circuit of claim 15 , wherein the accumulated difference is accumulated by dividing the difference for each respective bit period divided by the representation of the first data input for the respective bit period to yield a product of the division, and adding the product of the division across a number of bit periods.
18. The circuit of claim 15 , wherein the accumulated difference is accumulated by multiplying the difference for each respective bit period by the sign of the detected data output for the respective bit period to yield a product of the multiplication, and adding the product of the multiplication across the number of bit periods.
19. The circuit of claim 18 , wherein the accumulated difference does not include the product of the multiplication where the magnitude of the detected data output is less than a threshold value for a respective bit period.
20. The circuit of claim 15 , wherein the baseline compensation module includes a digital to analog converter.