| 摘要 |
PURPOSE:To perform radio analog transmission with good voice quality by converting a voice signal to frequencies in a frequency range which is much higher than its original frequency band, and performing one-bit quantization before transmission. CONSTITUTION:A voice signal from a terminal 1 is limited to frequency bands f1-f2 by a BPF2 while a frequency band which exerts no influence upon the voice quality are excluded, and the output of a sine wave oscillator 3 is adjusted to lower than the mean level of the voice signal and inputted to a synthesizer 4 to generate a composite signal. The output of a local oscillator 5 of high frequency f0 is modulated by a balanced modulator 6 with the composite signal and frequency-converted, and a BPF7 extracts (f0+f1)-(f0+f2), which are supplied to a one-bit quantizer 8 for one-bit quantization; and a BPF8 removes higher harmonics generated at the quantizer 8, and a one-bit quantized signal is outputted from an encoder output terminal 10. A decoder multiplies a signal from a terminal 11 by the output of a local oscillator 12 through a mixer 13 and the reproduced voice signal obtained by passing the output of the mixer through an LPF14 and a BPF15 is outputted from a terminal 16. |
