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This paper presents an all digital DS-CDMA upstream transmitter arid a head-end baseband receiver for upstream cable/HFC networks. The upstream transmitter supports frequency agility of the carrier, QPSK and QAM constellations up to 64QAM, variable symbol rates from 160kchip/s to 5.12Mchip/s increasing by power of two, and direct-digital up-conversion to achieve accurate amplitude and phase of modulation. The transmitter consists of pulse shaping filter, half-band filter, cascaded integrator-comb (CIC) filter, and inverse SINC filter. The all digital head-end baseband receiver supports programmable quadrature amplitude modulation up to 64QAM. Fast timing and carrier recovery algorithms are adopted for burst mode transmission. Code acquisition can be achieved within 2 symbols, and the carrier acquisition can be achieved within 31 symbols. All digital timing recovery is designed with ±200ppm symbol timing offset tolerance and the carrier recovery can compensate ±100ppm of carrier frequency offset.
Date of Conference: 2002