| 摘要 |
A carrier offset detection circuit is offered, which is provided to a demodulation circuit which demodulates a received signal subjected to FSK (Frequency Shift Keying) modulation, and which detects the offset of the carrier frequency between the transmitting side and the receiving side. A zero-crossing detection unit receives a digital base band signal indicating the level of the frequency shift (frequency deviation) of the received signal using the carrier frequency on the receiving side as a reference frequency, and detects a zero-crossing point of the base band signal and a base band signal obtained by delaying the former base band signal by one symbol, which occurs in a preamble period. A carrier offset detection circuit sets the offset value of the carrier frequency to the value of the base band signal at a timing of the zero-crossing point thus detected.
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