RF clock generator with spurious tone cancellation

摘要

A clock generator circuit may generate a target clock signal and may include a pattern generator to generate a pre-distorted version of a modulation signal from patterns stored by the pattern generator. An up-converter may up-convert the pre-distorted version of the modulation signal and a radio frequency lock oscillator signal to obtain an RF clock signal having a desired frequency tone. A tone detection circuit may receive the RF clock signal and detect a presence of unwanted tones. A controller may write the patterns corresponding to the pre-distorted version of the modulation signal to the pattern generator based on the detected unwanted tones in the RF clock signal.

主权项

1. A clock generation circuit for generating an RF clock signal, the clock generation circuit comprising:
a pattern generator to generate a pre-distorted version of a modulation signal from digital patterns stored by the pattern generator; an up-converter to mix the pre-distorted version of the modulation signal and a radio frequency local oscillator signal to generate the RF clock signal including a wanted tone corresponding to a desired frequency; a notch filter to filter the RF clock signal, wherein the notch filter is constructed to suppress a third order harmonic tone of the RF clock signal to prevent additional modulation tones introduced by a following clock driver or clock divider; a tone detection circuit to receive the filtered RF clock signal and to detect both amplitudes and phases corresponding to each of one or more unwanted tones having frequencies different from the desired frequency and being included in the RF clock signal; and a controller to generate pre-distortion data based on the detected amplitudes and phases and to control the pattern generator to generate the pre-distorted version of the modulation signal based on the pre-distortion data and to control the tone detection circuit to sequentially detect a plurality of the unwanted tones in the filtered RF clock signal; wherein the pattern generator additionally includes a pair of pattern generators to respectively generate an in-phase pre-distorted version of the modulation signal and a quadrature pre-distorted version of the modulation signal; and the tone detection circuit includes: a first mixer to receive the filtered RF clock signal as an input signal and down-convert the input signal based on the radio frequency local oscillator signal; and a second mixer to convert the down converted input signal to a signal that includes a baseband representation of one of the unwanted tones; and the controller controls the tone detection circuit with a variable signal at a selectable frequency of n-times a modulation signal frequency of the modulation signal, the variable signal being input to the second mixer and having frequencies at n harmonics of the modulation signal frequency, where n is a value sequentially varied by the controller to perform tone detection for different modulation signal frequency harmonics.