Patent ID: 7945609

Claim:
A method of composing a lookup table and searching indexes of the lookup table comprising the steps of: a) composing a lookup table of size N, where N is an integer using a subset of the range 2π to 2π using a sine function and a cosine function; b) setting a gain of a digital controlled oscillator (DCO) by using a value obtained from the lookup table; c)transforming an absolute value of the gain set in step b) to an integer value; d) determining a range of the integer value as one of 0 to N, N to 2N, 2N to 3N and 3N to 4N; e) searching an index of a sine function and an index of a cosine function according to the determined range of the integer value; and f) correcting a sign of a lookup table value corresponding to the searched index of the sine function and a sign of a lookup table value corresponding to the searched index of the cosine function according to the determined range of the integer value.