Frequency synthesizer using a hybrid analog/digital loop filter: A low complexity approach

A new frequency synthesizer using a hybrid analog/digital loop filter is presented. The digital loop filter employs a technique that allow resolution improvements without disturb the settling speed and using a low complexity circuit. Stability issues are addressed and the discrete-time equations of architecture are derived. A design example of a frequency synthesizer operating in an 850–1010 MHz band is shown, getting a tuning range of 4 × 40 MHz, 140 Hz of resolution and a reference noise suppression about 45.6 dB better than the conventional architecture.