Abstract: There is disclosed a method and apparatus for measuring a signal using a measurement system. The signal has a frequency component that is to be detected by the measurement. The frequency component has a varying phase. The signal has at least one interruption thereto. The method includes: processing the signal with the measurement system to detect the frequency component in the signal and stalling the measurement system before the start of the interruption. The stall period is calculated such that the processing of the signal is resumed: i) after the end of the interruption, and ii) where there is substantially no discontinuity between the phase of the frequency component in the signal at the end of the stall and in the phase of the frequency component in the signal at the beginning of the stall.

Abstract: There is disclosed a method and apparatus for measuring a signal using a measurement system. The signal has a frequency component that is to be detected by the measurement. The frequency component has a varying phase. The signal has at least one interruption thereto. The method includes: processing the signal with the measurement system to detect the frequency component in the signal and stalling the measurement system before the start of the interruption. The stall period is calculated such that the processing of the signal is resumed: i) after the end of the interruption, and ii) where there is substantially no discontinuity between the phase of the frequency component in the signal at the end of the stall and in the phase of the frequency component in the signal at the beginning of the stall.

Abstract: A method of generating a clock signal from a moving medium includes detecting movement of at least one mark that moves synchronously with the medium. A generally sinusoidal output signal corresponding to movement of the mark is produced. The generally sinusoidal output signal is interpolated to provide a clock signal having a higher frequency than said generally sinusoidal output signal. The interpolation dynamically adjusts the phase of the interpolated output clock signal to correct for errors in the phase of said output signal. In one embodiment, servo tracks are written to a magnetic disk using a servo pattern signal, the phase of the servo pattern signal being adjusted relative to a clock signal. In another aspect, timing errors in a servo track writer are characterised.