Local oscillator interference cancellation

摘要

Systems and methods for mitigating interference in a Local Oscillator (LO) signal generated by a Phase-Locked Loop (PLL) are disclosed. In one embodiment, a system includes a PLL and an error compensation subsystem. The PLL includes a Controlled Oscillator (CO) that provides a LO output signal based on a control signal, a phase detector that generates a phase detector output signal that is indicative of a phase error between a feedback signal that is a function of the LO output signal and a reference signal, and a loop filter that filters the phase detector output signal to provide the control signal for the CO. The error compensation subsystem applies, based on the phase detector output signal, a phase rotation to a signal derived from the LO output signal to thereby compensate for a phase error in the signal resulting from a phase error in the local oscillator output signal.

主权项

1. A system comprising:
a phase locked loop comprising:
a controlled oscillator adapted to provide a local oscillator output signal based on a control signal;a phase detector adapted to generate a phase detector output signal that is indicative of a phase error between a feedback signal that is a function of the local oscillator output signal and a reference signal; anda loop filter adapted to filter the phase detector output signal to provide the control signal for the controlled oscillator; a receiver chain comprising a first divider circuit adapted to divide the local oscillator output signal to thereby provide a frequency-divided local oscillator signal having a frequency that is a function of a frequency of the local oscillator output signal, the receiver chain further being adapted to:
downconvert a radio frequency signal based on the frequency-divided local oscillator signal to thereby provide a downconverted signal; andprocess the downconverted signal to provide a digital downconverted signal; and an error compensation subsystem adapted to apply, based on the phase detector output signal, a phase rotation to the digital downconverted signal to thereby compensate for a phase error in the digital downconverted signal resulting from a phase error in the local oscillator output signal indicated by the phase detector output signal, wherein the error compensation subsystem comprises:
a second divider circuit adapted to divide the phase detector output signal to thereby provide a modified phase detector output signal that is indicative of a phase error that is a function of the phase error indicated by the phase detector output signal;a phase rotator adapted to generate, based on the modified phase detector output signal, a compensation signal having a phase that corresponds to the phase rotation to be applied to the digital downconverted signal; anda multiplier adapted to multiply the compensation signal and the digital downconverted signal to thereby apply the phase rotation to the digital downconverted signal.