| 摘要 |
Apparatus for transmitting data spread across at least a portion of the bandwidth of a cable television channel comprises a carrier signal oscillator, a frequency divider, a pseudorandom sequence generator and two exclusive OR gates. A first exclusive OR gate serves to spread a data signal across the pseudorandom noise sequence generator having a much higher chip rate than the bit rate of the data signal. The second exclusive OR gate modulates the spread spectrum data signal to a carrier frequency for transmission over the cable television channel. The apparatus may be applied for return path transmission in the 0-30 megahertz band which is high susceptible to interference noise and provides approximately a 20 dB signal to interference ratio advantage over known data coding and transmission schemes. A microprocessor normally present in a cable television terminal may format data for transmission, control the spread spectrum modulation process and control gain control circuitry for introducing an appropriate power level into the cable plant. |
