Patent ID: 7218697

Claim:
A method of 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, the method comprising the steps of: assigning a positive or negative value to each of a plurality of positive and negative zero crossings of the first signal, a positive zero crossing being assigned a positive value if the second signal is negative or a negative value if the second signal is positive, and a negative zero crossing being assigned a positive value if the second signal is positive or a negative value if the second signal is negative; counting a numerator for a predetermined interval, the numerator being counted 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 being counted 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; counting a denominator for the predetermined interval, the denominator being counted in a positive direction; and calculating a raw phase between the first signal and the second signal by dividing a value of the numerator by a corresponding value of the denominator after the predetermined interval.