Invention Grant
US07656986B2 Low jitter phase rotator 有权
低抖动相位旋转器

Low jitter phase rotator
Abstract:
A phase rotator generates an output signal having plurality of possible output phases with reduced phase jitter. The low jitter phase rotator includes a plurality of differential amplifiers configured to receive a plurality of input differential signals having different phases, and configured to generate a plurality of weighted signals responsive to the plurality of input differential signals. A plurality of digital-to-analog converters (DAC) are arranged into a plurality of groups, each group of DACs configured to provide current for one of the corresponding differential amplifiers. The number of active DACs in each group of DACs determines a relative weighting of the weighted signals, where relative weighting determining an output phase of an output signal of the phase rotator. The DACs are configured to adjust the output phase of the phase rotator. At a kth phase, N/4 adjacent DACs are activated that are indexed as m0, m1, . . . m((N/4)−1), wherein N is the number of said plurality of DACs. At (k+1)th phase, a m(N/4) DAC is activated that is adjacent to the m((N/4−1) DAC. At (k+2)th phase, the m0 DAC is de-activated.
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