Direct digital frequency synthesizer using linear interpolator and counter and frequency synthesizing method thereof

摘要

PURPOSE: A DDFS(Direct Digital Frequency Synthesizer) using a linear interpolator and a counter and a method for synthesizing frequencies is provided to reduce a size of a ROM lookup table by using the linear interpolator and the counter. CONSTITUTION: A DDFS includes an accumulator(110), a ROM lookup table(120), a counter(130), an adder(140), a linear interpolator(150), and a multiplexer(160). The accumulator generates a phase control signal having a constant phase value according to an external digital signal. The ROM lookup table is used for storing the first amplitude value of the phase control signal. The counter is used for counting the second amplitude value of the phase control signal according to a phase value of the phase control signal. The adder is used for outputting an even sine value by adding the second amplitude value to the first amplitude value. The linear interpolator is used for interpolating an odd sine value on the basis of the even sine value. The multiplexer is used for generating an accurate sine value by multiplexing the even sine value and the odd sine value in response to the least significant bit received from the accumulator.