Method and system for direct digital up-conversion in a cable modem
First Claim
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1. A module for a cable modem termination system (CMTS), comprising:
- a digital modulator configured to up-convert, in a digital domain, a plurality of digital channels received in parallel, to one or more higher transmit frequency ranges in accordance with DOCSIS standards for CMTS downstream transmissions, the up-conversion being based on a first sampling frequency;
a digital to analog converter (DAC) coupled, at least indirectly, to the digital modulator to convert the up-converted digital channels to an analog format based on a second sampling frequency; and
a clock, coupled to the digital modulator and the DAC, configured to provide the first sampling frequency and the second sampling frequency, wherein the second sampling frequency is a multiple of the first sampling frequency.
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Abstract
Provided are a method and system for a module for a cable modem termination system. The module includes a digital modulator configured to block up-convert a plurality of digital channels and a digital to analog converter coupled, at least indirectly, to an output of the digital modulator to convert the digital channels to an analog format.
15 Citations
22 Claims
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1. A module for a cable modem termination system (CMTS), comprising:
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a digital modulator configured to up-convert, in a digital domain, a plurality of digital channels received in parallel, to one or more higher transmit frequency ranges in accordance with DOCSIS standards for CMTS downstream transmissions, the up-conversion being based on a first sampling frequency; a digital to analog converter (DAC) coupled, at least indirectly, to the digital modulator to convert the up-converted digital channels to an analog format based on a second sampling frequency; and a clock, coupled to the digital modulator and the DAC, configured to provide the first sampling frequency and the second sampling frequency, wherein the second sampling frequency is a multiple of the first sampling frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An up-conversion system for a cable modem termination system (CMTS) configured to simultaneously up-convert a plurality of digital channels, comprising:
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a combiner to combine the plurality of digital channels into a single digital bit-stream having an inverting and a non-inverting data component and representative of the plurality of digital channels; a digital modulator to modulate, in the digital domain, the digital bit-stream to one or more higher transmit frequency ranges in accordance with DOCSIS standards for CMTS downstream transmissions based on a first sampling frequency; a serializer to receive the modulated digital bit-stream from the digital modulator in parallel and to serialize the modulated digital bit-stream into a data stream based on a second sampling frequency; a digital to analog converter (DAC) for converting the data stream into one or more up-converted analog radio frequency output signals; and a clock to provide the first sampling frequency and the second sampling frequency, wherein the second sampling frequency is an integer multiple of the first sampling frequency. - View Dependent Claims (14, 15, 16)
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17. A method for testing a block up-converting module within a cable modem termination system (CMTS), the module including a digital modulator coupled to a digital to analog converter (DAC) and configured to up-convert, in a digital domain, a plurality of digital channels to one or more higher transmit frequency ranges in accordance with DOCSIS standards for CMTS downstream transmissions, the up-conversion being based on a first sampling frequency, the method comprising:
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providing first and second sampling signals to the block up-converting module; multiplexing one or more fixed input words with an output of the digital modulator to produce a multiplexed signal based on the first sampling signal; providing the multiplexed signal as an input to the DAC based on a second sampling frequency; and comparing an output of the DAC with an analog signal based on the one or more fixed input words, wherein the second sample frequency is an integer multiple of the first sampling frequency. - View Dependent Claims (18, 19, 20)
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21. A up-conversion module for up-converting a plurality of digital channels in a cable modem termination system (CMTS), comprising:
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a combiner module, configured to combine the plurality of digital channels into a single bit stream; an interpolation filter and up-converter module, logically coupled to the combiner module, configured to interpolate and filter a portion of the single bit stream to produce a modulated output stream at a first sampling frequency, wherein the modulated output stream comprises a plurality of bits for each bit of the portion of the single bit stream, and the modulated output stream for the portion is produced in parallel; a serializer module, coupled to the interpolation filter and up-converter module, configured to serialize the modulated output stream; a digital to analog converter (DAC) module, coupled to the serializer module, configured to convert the serialized modulated output stream to an analog format at a second sampling frequency; and a clock, coupled to the combiner module, the interpolation filter and up-converter module, the serializer module, and the DAC module, configured to provide first and second sampling signals for synchronizing the up-conversion, wherein the second sampling frequency is a multiple of the first sampling frequency.
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22. An up-conversion system for a cable modem termination system (CMTS) configured to simultaneously up-convert a plurality of digital channels, comprising:
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a combiner to combine the plurality of digital channels into a single digital bit-stream; a digital modulator to modulate, in the digital domain, the digital bit-stream based on a first sampling frequency, wherein the modulation is performed simultaneously on each of the digital channels of the plurality of digital channels, and the modulated digital bit-stream comprises a plurality of parallel data paths; a serializer to serialize the modulated digital bit-stream into a data stream based on a second sampling frequency; a digital to analog converter (DAC) for converting the data stream into an up-converted analog radio frequency output signals based on the second sampling frequency; and a clock to provide the first sampling frequency and the second sampling frequency, wherein the second sample frequency is higher than the first sampling frequency.
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Specification