Data storage device with asynchronous position error signal demodulation with split burst servo patterns

A method comprising:

• receiving, by an asynchronous demodulation module of control circuitry of a data storage device, demodulated split null burst signals based on a selected head reading a first set of bursts and a second set of bursts in a split null burst servo pattern of a corresponding disk surface;
• and
• outputting, by the asynchronous demodulation module and based on the demodulated split null burst signals, a radial position signal indicative of a radial position of the selected head,
• wherein:
• the first set of bursts comprises a first burst and a third burst each at a same first radial location on the corresponding disk surface;
• the second set of bursts comprises a second burst at a second radial location on the corresponding disk surface different than the first radial location;
• the first burst, the second burst, and the third burst are disposed in an alternating manner along a longitudinal direction of a track containing the split null burst servo pattern;
• the first burst and the third burst each have a first length in the longitudinal direction;
• the second burst has a second length in the longitudinal direction different than the first length;
• and
• wherein the receiving and the outputting are performed by one or more processing devices individually or in combination.

One or more processing devices, individually or in combination, comprising an asynchronous demodulation module of control circuitry of a data storage device, the asynchronous demodulation module comprising:

• means for receiving demodulated split null burst signals based on a selected head reading a first set of bursts and a second set of bursts in a split burst servo pattern of a corresponding disk surface;
• and
• means for outputting, based on the demodulated split null burst signals, a radial position signal, indicative of a radial position of the selected head,
• wherein the demodulated split null burst signals comprise:
• a first demodulated split null burst signal based on summing a first trigonometric function of respective values of a digital read-back signal sampled at respective bursts of the first set of bursts;
• a second demodulated split null burst signal based on summing a second trigonometric function of the respective values of the digital read-back signal sampled at the respective bursts of the first set of bursts;
• a third demodulated split null burst signal based on summing the first trigonometric function of respective values of the digital read-back signal sampled at respective bursts of the second set of bursts;
• and
• a fourth demodulated split null burst signal based on summing the second trigonometric function of the respective values of the digital read-back signal sampled at the respective bursts of the second set of bursts.