| 摘要 |
PURPOSE: A digital cordless telephone set of a direct spreading pattern is provided to increase channel efficiency using a short spreading code and to offer a simplified spreading/despreading modem. CONSTITUTION: A digital cordless telephone set of a direct spreading pattern is provided with a voice codec(12), a spreading/despreading modem(14,15) and a wireless modem(16). The voice codec(12) executes sampling for a transmitting analog voice signal(AV_TX) inputted through a microphone(M) as 64Kbps. Also the voice codec(12) converts the sampled signal into an ADPCM(Adaptive Differential Pulse Code Modulation) signal and generates a compressed transmitting digital voice signal(DV_TX). A receiving digital voice signal(DV_RX) inputted from a despreading part(14) of the spreading/despreading modem(14,15) is first decoded into a receiving analog voice signal(AV_RX) and then outputted to a speaker(S). The spreading/despreading modem(14,15) is composed of the spreading part(14) and a despreading part(15). The spreading part(14) directly spreads the transmitting digital voice signal(DV_TX) into a transmitting spreading signal(SS_TX) using a spreading code of 22 chips every 2 bits. The despreading part(15) despreads a receiving spreading signal(SS_RX) into the receiving digital voice signal(DV_RX). The wireless modem(16) modulates the receiving spreading signal(SS_RX) into a transmitting RF signal(RF_TX) and demodulates a receiving RF signal into the receiving spreading signal(SS_RX).
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