| 摘要 |
PROBLEM TO BE SOLVED: To provide a digital radio speech communication circuit capable of performing full-duplex communication without requiring a CODEC nor an echo canceler. SOLUTION: A speech input AI is converted by an acoustic input section 11 into an electric signal, which is supplied to aΔΣmodulation section 13 through an LPF 12. TheΔΣmodulation section 13 generates a continuous low/high density digital signal varying in density in accordance with the varying speed of the signal level of the speech input AI. The low/high density digital signal is time-compressed into time-division frames by a speed conversion section 14 and constituted by a transmission frame processing section 15 into transmission frames, which are then modulated by an FSK modulation section 16 and transmitted from an antenna 19. A radio signal RF received from an opposite device is demodulated by an FSK demodulation section 20 and a reception frame processing unit 21 extracts reception frames. The reception frames are restored by a speed conversion section 22 to a continuous low/high density digital signal, which is converted by an LFP 23 into a speech signal, so that the speech signal is output as a speech output AO from an acoustic output section 24. COPYRIGHT: (C)2008,JPO&INPIT
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