| 摘要 |
<p>Since the frequency band after spectrum spreading modulation is wide, 2.4 GHz frequency of the ISM band is specified as a modulation carrier frequency and it is conventionally impossible to apply the spectrum spreading communication method to transmission of frequency other than 2.4 GHz. By the present invention, it is possible to obtain a noise reduction effect equivalent to the spectrum spreading communication even in the signal transmission of frequency other than the 2.4 GHz band. Spectrum spreading modulation is performed only at the reception side. A noise reduction apparatus includes a differentiation circuit for converting a pulse string (SS signal) into a saw-tooth pulse string signal, means for performing pulse width modulation of the converted saw-tooth pulse string signal by an input signal, and means for outputting the input signal which has been pulse-width modulated into a saw-tooth pulse string signal as an output signal only when the input signal which is pulse-width modulated into the saw-tooth string signal is above a predetermined level.</p> |
