DITHERING A DIGITALLY-CONTROLLED OSCILLATOR OUTPUT IN A PHASE-LOCKED LOOP

摘要

digitally controlled oscillator (DCO) of the PLL is dithered DCO_OUT dither signal is a frequency change intervals have. In one example, DCO receives a stream of incoming digital tuning words that are not dithered, receives the dithered reference clock signal (REFD), and outputs a signal generated by DCO_OUT its frequency variation interval is dithered. If the PLL is used in the local oscillator of a cellular telephone transmitter, the novel dithering a frequency less than the spread of digital image noise digital image noise of the DCO are present in a certain frequency offset from the main local oscillator frequency. The proliferation of digital image noise according to the noise frequency should be satisfied specifications without having to increase the frequency of the PLL reference clock. By satisfying the noise specifications to avoid increasing the frequency of the reference clock, the increase in power consumption is avoided. ;