| 摘要 |
The present invention provides a DeltaSigma modulator of a frequency modulation system that can lessen the requirement of linearity for an oscillator. A DeltaSigma modulator comprises an oscillating apparatus that changes a frequency thereof according to an input signal, a quantizing means for quantizing a frequency modulation signal output from the oscillating apparatus, and an operation means for applying an operation to a digital signal output from the quantizing means. The oscillating apparatus comprises an oscillator that changes a frequency thereof according to the input signal, a reference signal source that outputs a reference signal at a predetermined frequency, a mixer that receives the signals from the oscillator and the reference signal source, and a low-pass filter that passes a low frequency component of a signal output from the mixer. The center oscillation frequency of the oscillator is set higher than a target center oscillation frequency of the frequency modulation signal.
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