Digital phase detector for periodically alternating signals

A digital phase detector for determining a phase between a first signal and a second signal, the first signal and the second signal corresponding to signal transmissions between a first device and a second device, the second device periodically moving along a translational axis with respect to the first device in a first direction or a second direction, said digital phase detector comprising:

• a polarity determiner for assigning a positive or negative value to each of a plurality of positive and negative zero crossings of the first signal, said polarity determiner assigning a positive zero crossing a positive value if the second signal is negative or a negative value if the second signal is positive, said polarity determiner assigning a negative zero crossing a positive value if the second signal is positive or a negative value if the second signal is negative;
• a numerator counter for counting for a predetermined interval, the numerator counter counting in a positive direction if the second device is moving in the first direction and the value assigned to a corresponding zero crossing of the first signal is negative or if the second device is moving in the second direction and the value assigned to the corresponding zero crossing is positive, the numerator counter counting in a negative direction if the second device is moving in the first direction and the value assigned to the corresponding zero crossing is positive or if the second device is moving in the second direction and the value assigned to the corresponding zero crossing is negative;
• a denominator counter for counting in a positive direction for the predetermined interval;
• and
• a raw phase calculator for calculating a raw phase between the first signal and the second signal by dividing a value of the numerator counter by a corresponding value of the denominator counter after the predetermined interval.