| 摘要 |
In a frequency conversion circuit and a modulation circuit, a filter having an impulse response (HB(z); HL(z)) corresponding to a rectangular pulse wave multiplied by a cosine wave of f3/4 is a band pass type filter having a center frequency of f3/4, and the transfer function H(z) of the filter is expressed in the form of a sum of series. When a numerator part of the transfer function is arranged to be processed with a low-speed sampling frequency f2 and a denominator part is to be processed with a high-speed sampling frequency f3 (=Lxf2, L: odd number), the circuit can be made to have an adjustment-free structure and small in size. Further, when an output of processing of the numerator part based on the low-speed sampling frequency f2 is subjected to a D/A conversion while processing of the denominator part based on the high-speed f3 is implemented by a switched capacitor circuit, power consumption can be reduced.
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