| 摘要 |
PROBLEM TO BE SOLVED: To faithfully reproduce the duty of a transmission data pulse signal, while being an amplitude shift keying (ASK) receiving circuit using a logarithmic amplifier. SOLUTION: A signal S4 to be modulated is logarithm-compressed by the logarithmic amplifier 11, and detected by a wave detection circuit 12. A DC interruption circuit 13 removes a DC component from a wave detection signal S6 being the output of the wave detection circuit 12. The DC removal signal S7 is index-extended by an anti-logarithmic amplifier 14. A pulse signal S10 is output from a comparing circuit 17 through the use of the index extension signal S8. The DC component is previously removed by the DC interruption circuit 13 in the pre-stage of the anti-logarithmic amplifier 14, thereby allowing the dynamic range of the index extension signal S8 is made to be within the range of the operation voltage of an IC. The index extension signal S8, which is returned to have a linear waveform by the anti-logarithmic amplifier 14, faithfully reproduces the signal waveform in transmission. Thus, the duty radio of the pulse signal in transmission is kept to be excellent concerning the pulse signal S10 to be output in an ASK receiving circuit 10. COPYRIGHT: (C)2009,JPO&INPIT
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