Sampling frequency conversion apparatus and fractional frequency dividing apparatus for sampling frequency conversion

摘要

The invention provides a sampling frequency conversion apparatus which converts a sampling frequency to another frequency using another oscillator employed in the system as the source oscillator. A fractional frequency divider divides an output of the source oscillator by a non- integer. By using outputs of the source oscillator and the divider individually as sampling clocks, an input signal is first sampled by a first sampling circuit and then an output of the first sampling circuit is sampled again by a second sampling circuit to convert the sampling frequency. The fractional frequency divider divides the clock signal of a higher one of the frequencies to produce the clock signal of a lower one of the frequencies, and the dividing ratio of the fractional frequency divider for the production of the clock signal is varied periodically to effect division of a frequency ratio having a fractional value when averaged over a time period.