Abstract
The United States industrial, scientific, and medical (ISM) band has been released for spread spectrum communication, and various applications for it are being proposed. A spread spectrum cordless telephone set has been developed for domestic use as one of its applications.
In this paper, the design outline and its characteristics are explained. the direct sequence spread spectrum technique with spreading ratio of 16 in the 902β to 928β MHz ISM band is used. to solve the nearβfar problem in the mobile radio communication channel, the frequency division multiple accessβtime division duplex (FDMA TDD) technique is adopted where different frequencies can be assigned to each channel. Compact size and low power consumption is achieved by developing a chip in which spread spectrum processing and transceiver multi plexing can be handled on a single ASIC chip.
The voice codec uses ADPCM and provides better voice quality compared to the conventional analog cordless phones. Wider talking range compared to the conventional 46/49 MHz cordless phone is obtained by increasing the amount of transmitted power. Moreover, since the ISM band is used, interference from other sources can be avoided by changing the channel frequencies.