Data storage device with notch filter calibration based on multi-rate excitation and error rejection

A method comprising:

• applying, by the one or more processing devices, coefficients for a multi-rate notch filter to a servo control loop;
• measuring, by the one or more processing devices, a multi-rate error rejection transfer function;
• determining, by the one or more processing devices, whether a peak of the multi-rate error rejection transfer function is greater than a multi-rate error rejection transfer function threshold;
• and
• modifying, by the one or more processing devices, responsively to determining that the peak of the multi-rate error rejection transfer function is not greater than a multi-rate error rejection transfer function threshold, the parameters of the multi-rate notch filter based at least in part on the peak of the multi-rate error rejection transfer function.

One or more processing devices comprising:

• means for receiving parameters of a multi-rate notch filter;
• means for determining coefficients for the multi-rate notch filter, based at least in part on the parameters of the multi-rate notch filter;
• means for applying the coefficients for the multi-rate notch filter to a servo control loop;
• means for measuring a multi-rate error rejection transfer function;
• means for determining whether a peak of the multi-rate error rejection transfer function is greater than a multi-rate error rejection transfer function threshold;
• and
• means for modifying, responsively to determining that the peak of the multi-rate error rejection transfer function is not greater than a multi-rate error rejection transfer function threshold, the parameters of the multi-rate notch filter based at least in part on the peak of the multi-rate error rejection transfer function, thereby modifying the peak of the multi-rate error rejection transfer function to be not greater than the multi-rate error rejection transfer function threshold.