| 摘要 |
PURPOSE: A numerically controlled oscillator of a digital phase locked circuit is provided to simplify a circuit structure by using a characteristic of the trigonometric function. CONSTITUTION: A numerically controlled oscillator(NCO) comprises: an input slicer for outputting a read only memory(ROM) address and code controlled signal by slicing an input address(x); an offset ROM for storing values of sin(a) and cos(a) sampled at regular intervals out of values from 0 to pi/2, and outputting corresponding data by the ROM address output from the input slicer; a segment ROM for storing values of sin(b) and cos(b) sampled at regular intervals out of values from 0 to pi/2, and outputting corresponding data by the ROM address output from the input slicer; an operation block for outputting values of sin(r) and cos(r) by carrying out an operation of data values of sin(a), cos(a) output from the offset ROM and sin(b), cos(b) output from the segment ROM; and an output format unit for determining and outputting codes of the last output values, sin(x) and cos(x) by the code controlled signal when values of sin(r) and cos(r) are inputted.
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