DITHER-LESS ERROR FEEDBACK FRACTIONAL-N FREQUENCY SYNTHESIZER SYSTEMS AND METHODS

摘要

A fractional-N divider of a frequency synthesizer is driven by a dither-less error feedback modulator to alleviate fractional spurious tones introduced by the cyclic train of division ratios from delta-sigma modulators. A first feedback loop generates the feedback signal. A second feedback loop disrupts fractional spurious tones and a third feedback loop provides approximately zero static error.

主权项

1. A delta sigma modulator comprising:
a combining circuit configured to combine an input signal, an output of a divider circuit, and a feedback signal to form a summed signal; a quantizing circuit configured to quantize the summed signal to form a cyclic output code; a gain component configured to scale the cyclic output code to generate a scaled signal; and a summing circuit configured to combine the summed signal, the cyclic output code, and the scaled signal to provide the feedback signal.