PLL frequency synthesizer architecture for low phase noise and reference spurs

摘要

A frequency synthesizer for use in a transceiver generates a relatively high reference frequency with fine frequency resolution and low in-band phase noise by using a digital processor to generate a digital reference signal at a finely-tuned reference frequency. A Digital-to-Analog Converter (DAC) converts the digital reference signal to an analog reference signal, and a low pass filter filters the analog reference signal to produce a filtered analog reference signal. The frequency synthesizer further includes a phase locked loop for up-converting the filtered analog reference signal from an IF signal to an RF signal.