Bandpass component decimation and transmission of data in cable television digital return path

A device for use in a cable television return path, comprising:

• an analog-to-digital converter configured to convert an analog return signal to a first stream of digital samples at a first data rate;
• a bandpass interpolation filter configured to receive the first stream of digital samples and to substantially remove signals outside of a predetermined frequency band;
• up-sampling logic configured to up-sample outputs of the bandpass interpolation filter and to generate a second stream of digital samples at a second data rate, the second data rate being a predetermined multiple of a center frequency of the predetermined frequency band;
• separation logic configured to separate the second stream of digital samples into a third stream of digital samples and a fourth stream of digital samples, the third stream and the fourth stream each having a data rate that is one half of the second data rate;
• interpolation filters configured to filter the third stream and the fourth stream;
• down-sampling logic configured to select digital samples from the outputs of the interpolation filters and to interleave the selected digital samples to form a fifth stream of digital samples, the fifth stream having a third data rate that is higher than four times the bandwidth of the predetermined frequency band but lower than the first data rate;
• and
• a serializer configured to convert the fifth stream of digital samples to a serial bit stream;
• an optical transmitter driven by the serial bit stream to generate an optical signal for transmission in the return path of the cable television system.

A signal decoder for use in a cable television return path and configured to receive a first stream of digital samples that include first digital samples interleaved with second digital samples of signals within a predetermined frequency band, the signal decoder comprising:

• a deinterleaver configured to deinterleave the first stream of digital samples and generate a stream of first digital samples and a stream of second digital samples;
• interpolation filters configured to filter the stream of first digital samples and the stream of second digital samples;
• up-sampling logic configured to up-sample the outputs of the interpolation filters to form a first up-sampled stream and a second up-sampled stream of digital samples, the first up-sampled stream and the second up-sampled stream both having a data rate that is a predetermined multiple of a center frequency of the predetermined frequency band;
• combining logic configured to combine the first up-sampled stream and the second up-sampled stream to generate a combined stream of digital samples;
• and
• a bandpass interpolation filter configured to filter the combined stream to generate an output stream of digital samples at an output data rate higher than that of the first stream of digital samples.

A device for use in a cable television return path, comprising:

• an optical data receiver configured to receive an optical signal from an optical medium and to convert the optical signal to a serial bit stream;
• a deserializer configured to convert serial bit stream into a first stream of digital samples each having a plurality of bits;
• a deinterleaver configured to deinterleave the first stream of digital samples and generate a stream of first digital samples and a stream of second digital samples;
• interpolation filters configured to filter the stream of first digital samples and the stream of second digital samples;
• up-sampling logic configured to up-sample the outputs of the interpolation filters to form a first up-sampled stream and a second up-sampled stream of digital samples, the first up-sampled stream and the second up-sampled stream both having a data rate that is a predetermined multiple of a center frequency of the predetermined frequency band;
• combining logic configured to combine the first up-sampled stream and the second up-sampled stream to generate a combined stream of digital samples;
• a bandpass interpolation filter configured to filter the combined stream to generate an output stream of digital samples at an output data rate higher than that of the first stream of digital samples;
• and
• a digital-to-analog converter configured to convert the output stream of digital samples to an analog signal.

A method of transmitting analog return signals in a digital return path of a cable television system, the method comprising:

• converting an analog return signal to a first stream of digital samples at a first data rate;
• filtering the first stream of digital samples to substantially remove signals outside of a predetermined frequency band;
• up-sampling the filtered stream of digital samples to generate a second stream of digital samples at a second data rate, the second data rate being a predetermined multiple of a center frequency of a predetermined frequency band;
• separating the second stream of digital samples into a third stream of digital samples and a fourth stream of digital samples, the third stream and the fourth stream each having a data rate that is one half of the second data rate;
• filtering the third stream and the fourth stream;
• down-sampling the filtered third stream and the filtered fourth stream of digital samples;
• interleaving digital samples from the down-sampled streams to form a fifth stream of digital samples, the fifth stream having a third data rate that is higher than four times the bandwidth of the predetermined frequency band but lower than the first data rate;
• converting the fifth stream of digital samples to an optical signal for transmission in the return path of the cable television system.

A signal encoder for use in a cable television return path and configured to receive a first stream of digital samples from an analog-to-digital converter, the first stream of digital samples being representative of an analog return path signal that is sampled at a first data rate, the signal encoder comprising:

• a bandpass interpolation filter configured to receive the first stream of digital samples and to substantially remove signals outside of a predetermined frequency band;
• up-sampling logic configured to up-sample outputs of the bandpass interpolation filter and to generate a second stream of digital samples at a second data rate;
• separation logic configured to separate the second stream of digital samples into a third stream of digital samples and a fourth stream of digital samples;
• interpolation filters configured to filter the third stream and the fourth stream;
• and
• down-sampling logic configured to select digital samples from the outputs of the interpolation filters and to interleave the selected digital samples to form a fifth stream of digital samples, the fifth stream having a third data rate that is lower than the first data rate.

A signal decoder for use in a cable television return path and configured to receive a first stream of digital samples that include first digital samples interleaved with second digital samples of signals within a predetermined frequency band, the signal decoder comprising:

• a deinterleaver configured to deinterleave the first stream of digital samples and generate a stream of first digital samples and a stream of second digital samples;
• interpolation filters configured to filter the stream of first digital samples and the stream of second digital samples;
• up-sampling logic configured to up-sample the outputs of the interpolation filters to form a first up-sampled stream and a second up-sampled stream of digital samples;
• combining logic configured to combine the first up-sampled stream and the second up-sampled stream to generate a combined stream of digital samples;
• and
• a bandpass interpolation filter configured to filter the combined stream to generate an output stream of digital samples at an output data rate higher than that of the first stream of digital samples.