| 摘要 |
A digitally controlled oscillator in a digital phase-locked loop provides an additional output signal which indicates the time difference between clock pulses output from the digitally controlled oscillator and clock pulses of an ideal clock signal of the same average frequency. This additional signal is called a residue signal. This residue signal may then be used to extrapolate or interpolate outputs of continuously variable interpolation or decimation filters using the output clock signal of the digital phase-locked loop generated according to the digitally controlled oscillator. Because the residue signal may be used in interpolation or decimation filters, it is also applicable to analog-to-digital converters, digital-to-analog converters and sample rate converters which use such filters. The digital phase-locked loop circuit is simpler than previous circuits because a conventional overflowing accumulator may be used, which is a first order system, rather than a higher order multi-bit noise shaper. Additionally, a simpler interpolation or decimation filter may be used.
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