System and methods for efficient digitization in hybrid fiber-coaxial networks
An analog signal processor includes a sampling unit configured to (i) filter, in the frequency domain, a received time domain analog signal into a low-frequency end of a corresponding frequency spectrum, (ii) sample the filtered analog signal at a frequency substantially higher than the low-frequency end, and (iii) spread quantization noise over an expanded Nyquist zone of the corresponding frequency spectrum. The processor further includes a noise shaping unit configured to shape the spread quantization noise out of the low-frequency end of the corresponding frequency spectrum such that the filtered analog signal and the shaped quantization noise are substantially separated in the frequency domain, and a quantization unit configured to apply delta-sigma modulation to the filtered analog signal using at least one quantization bit, and output a digitized bit stream that substantially follows the amplitude of the received time domain analog signal.
1. A transmitting signal processor in operable communication with a first end of a digital transport medium, comprising:
a sampler configured to (i) filter, in the frequency domain, a received time domain analog signal into a low-frequency end of a corresponding frequency spectrum, (ii) sample the filtered analog signal at a frequency substantially higher than the low-frequency end, and (iii) spread quantization noise over an expanded Nyquist zone of the corresponding frequency spectrum;
a noise shaper configured to implement a noise transfer function to shape the spread quantization noise out of the low-frequency end of the corresponding frequency spectrum such that the filtered analog signal and the shaped quantization noise are substantially separated in the frequency domain, wherein the noise transfer function is configured to correspond with a passive filter of a receiving processor disposed at a second end of the digital transport medium opposing the first end; and
a quantizer configured to apply delta-sigma modulation to the filtered analog signal using at least one quantization bit, and output to the digital transport medium a digitized bit stream that substantially follows the amplitude of the received time domain analog signal.
2. The transmitting processor of claim 1 , wherein the received time domain analog signal is a data over cable service interface specification radio frequency signal.
3. The transmitting processor of claim 1 , wherein the delta-sigma modulation uses a one-bit quantization.
4. The transmitting processor of claim 3 , wherein the output digitized bit stream comprises a binary on/off key signal.
5. The transmitting processor of claim 3 , wherein the output digitized bit stream comprises a PAM4 signal.
6. The transmitting processor of claim 1 , wherein the delta-sigma modulation uses a two-bit quantization.