Abstract: A detector for detecting a locked state and an out-of-lock state of a phase locked loop includes an out-of-lock detector circuit that receives a reference signal and an input signal representing a PLL oscillator signal. The out-of-lock detector detects an out-of-lock state of the PLL and generates an out-of-lock signal indicating whether an out-of-lock state is detected. The detector further includes a lock detector circuit that receives the reference signal and the input signal, detects a locked state of the PLL, and generates a lock signal indicating whether a locked state is detected. A logic circuit receives both the out-of-lock signal and the lock signal and combines both signals to obtain an output signal indicative of whether the PLL is in a locked state or an out-of-lock state.

Abstract: An RF transceiver circuit is disclosed herein. In accordance with one example of the disclosure the RF transceiver circuit includes a phase-locked-loop (PLL) with a fractional-N multi-modulus divider. The PLL operates in accordance with a PLL clock frequency and generates a frequency modulated RF output signal. The RF transceiver circuit further includes a modulator unit, which is configured to generate a sequence of division values dependent on a set of modulation parameters. The modulator operates in accordance with a system clock frequency, which is lower than the PLL clock frequency. A sample rate conversion unit is coupled between the modulator unit and a fractional-N multi-modulus divider. The sample rate conversion unit is configured to interpolate the sequence of division ratios to provide an interpolated sequence of division ratios at a rate corresponding to the PLL clock frequency.