| 摘要 |
PROBLEM TO BE SOLVED: To provide a frequency modulation circuit which reduces noise present in a frequency band which requires low noise, and operates with low distortion, high efficiency and low noise. SOLUTION: A bandpass type delta sigma modulation section 15 performs delta sigma modulation on an inputted modulation signal such that quantization noise is reduced in a frequency band which requires low noise. An LPF 16 removes a noise component in a high frequency region from the signal on which the delta sigma modulation has been performed. A frequency modulation circuit 1 reduces noise in the frequency band which requires low noise with the bandpass type delta sigma modulation section 15 and the LPF 16, and reduces noise in the vicinity of a direct current component DC with a feedback comparison section 11 and a loop filter 12. COPYRIGHT: (C)2008,JPO&INPIT
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