| 摘要 |
Since the frequency band after the spread spectrum modulation is wide, the frequency of 2.4 GHz band of the ISM (Industrial Scientific Medical) band as a modulation carrier frequency, is specified, so that the current state, in which the spread spectrum communication system can not be applied to the transmission by the frequencies other than 2.4 GHz band, is considered, and thus the noise reduction effect equal with the spread spectrum communication system was obtained in the signal transmission in the frequencies other than 2.4 GHz band, thereby obtaining a construction, in which the spread spectrum modulation is performed only at receiving side. Noise reduction apparatus according to the present invention comprises a differentiating circuit for converting pulse string (SS signal) into sawtooth pulse string signal, means for pulse-width-modulating the converted sawtooth pulse string signal with input signals, and means for outputting the sawtooth pulse string signals which are pulse-width modulated with the above input signal as an output signal, only at the time during which the pulse-width-modulated sawtooth pulse string signal is more than a given level.
|
