METHOD FOR IMPROVING THE PRECISION OF PLL RESOLUTION BY USING A DDS, ESPECIALLY CONCERNED WITH INCREASING THE PRECISION OF PLL OUTPUT RESOLUTION BY INSTALLING A HIGH-SPEED DDS IN ORDER TO DIRECTLY CONTROL A FREQUENCY VALUE AT THE EXTERNAL

摘要

PURPOSE: A method for improving the accuracy of PLL resolution using a DDS(Direct Digital Synthesizer) is provided to create and supply an RX_LO frequency(1727.3744MHz), required in a predistortion system, and to increase the reliability of a test result by installing a high-speed DDS and controlling a frequency value at the external directly so as to increase the precision of PLL output resolution. CONSTITUTION: A reference clock, inputted to a DDS(200), is determined as a DDS output frequency by a frequency tuning word embedded in the DDS(200). As the output frequency is inputted to a PLL oscillator(400) through a BPF(Band Pass Filter)(300), a Fvco is determined. An RX_LO frequency of 1712.374MHz is generated in order to create the 137.6265MHz IF(Intermediate Frequency) of a down conversion path, supplied to a frequency down converter in a pre-distortion system from an SNCA(Synthesizer Card Assembly) board.