Full band cable receiver
Systems and methods are described for the implementation of a full band cable receiver by using a combination of tuners (e.g., ultra-low power Tuners) and Analog-to-Digital Converters (ADCs) to attain the goal of digitization with reduced power and/or cost. The full-band capture cable receiver can overcome the constraints of conventional cable receiver systems and deliver multiple channels, thereby allowing operators to provide consumers with an increased number of services.
1. An apparatus for digitizing the full band of a cable signal, the apparatus comprising:
an input for receiving the cable signal;
a plurality of tuners configured to receive the cable signal from the input and produce a plurality of frequency segments of the cable signal, wherein each frequency segment covers a portion of the cable signal;
a plurality of analog-to-digital converters (ADCs) configured to receive the cable signal from the plurality of tuners and produce an output stream, each ADC coupled to a single tuner of the plurality of tuners, wherein each tuner provides the frequency segment of the cable signal to the ADC; and
a digital signal processor (DSP) configured to receive the output stream from the plurality of ADCs, filter one or more channels of the output stream and compensate the one or more channels for in-phase quadrature (I/Q) imbalance, wherein the DSP further comprises:
a demultiplexer configured to contain a mapping from the plurality of tuners to a plurality of RF channels;
an image rejection filter configured to estimate an in-phase quadrature (IQ) imbalance for each RF channel separately and to compensate for the IQ imbalance in the RF channel;
a channel selection filter configured to filter adjacent channels and interfering RF channels for each RF channel;
a down converter configured to convert the cable signal into a lower frequency; and
a rate converter that converts the down-converted signal into a specified frequency for reception at a demodulator.
2. The apparatus of claim 1 , wherein the cable signal comprises an entire band from 50 megahertz (MHz) to 1 gigahertz (GHz) frequencies, and wherein the plurality of tuners include eight tuners that subdivide the cable signal into eight frequency segments.
3. The apparatus of claim 1 , wherein the DSP produces output data on a first serial bus and a second serial bus, and wherein the output data on the first serial bus contains data for sixteen channels and wherein the output data on the second serial bus contains data for sixteen channels.
4. The apparatus of claim 1 , wherein at least one of the plurality of frequency segments is of 120 megahertz (MHz) bandwidth.
5. The apparatus of claim 1 , wherein the plurality of frequency segments includes eight frequency segments that are obtained by using four synthesizers.
6. The apparatus of claim 1 , wherein the cable signal comprises an entire band from 50 megahertz (MHz) to 1 gigahertz (GHz) frequencies, and wherein the plurality of tuners include at least five tuners that subdivide the cable signal into at least five frequency segments.
7. The apparatus of claim 1 , wherein each frequency segment is of at least 50 megahertz (MHz) bandwidth.
8. A method for digitizing a cable signal, the method comprising:
receiving an incoming cable signal;
dividing the received cable signal into a plurality of frequency segments, each frequency segment covering a portion of the incoming cable signal;
passing each frequency segment of the cable signal through a separate tuner of a plurality of tuners, the separate tuner producing an output stream;
passing the output stream of the separate tuner to an analog-to-digital converter that digitizes the output stream of the separate tuner; and
passing the digitized output stream from the analog-to-digital converter to a digital signal processor (DSP) configured to filter one or more channels of the digitized output stream and compensate the one or more channels for in-phase quadrature (I/O) imbalance.
9. The method of claim 8 , wherein a full band of the incoming cable signal from 50 megahertz (MHz) to 1 gigahertz (GHz) frequencies is divided into the plurality of frequency segments, the plurality of frequency segments including at least five frequency segments.
10. The method of claim 8 , wherein the DSP further comprises:
a demultiplexer;
an image rejection filter;
a channel selection filter;
a down converter; and
a rate converter.
11. The method of claim 8 , wherein the DSP is coupled to a first serial bus and a second serial bus, and wherein the DSP produces an output signal that carries data for sixteen channels on each of the first serial bus and the second serial bus.
12. The method of claim 8 , wherein each frequency segment is of at least 50 megahertz (MHz) bandwidth.
13. The method of claim 8 , wherein passing each frequency segment of the cable signal through a separate tuner further includes:
passing the frequency segment of the cable signal to at least one radio frequency (RF) mixer; and
passing an output signal of the RF mixer to at least one low-pass filter (LPF).
14. The method of claim 8 , wherein dividing the received cable signal into a plurality of frequency segments further includes:
employing four synthesizers to produce the frequency segments for eight tuners, wherein at least a portion of the tuners are provided with the frequency segment by dividing the frequency produced by one of the synthesizers.
15. A system for digitizing a cable signal, the system comprising:
an input for receiving the cable signal;
a low-noise amplifier (LNA) configured to receive the cable signal;
at least one radio frequency (RF) buffer that receives the cable signal from the LNA and provides the cable signal to a plurality of RF amplifiers;
a plurality of band pass filters that receive the cable signal from the plurality of RF amplifiers and provide the signal to a plurality of RF mixers;
a plurality of low pass filters (LPF) that receive the cable signal from the plurality of RF mixers and provide the cable signal to a plurality of analog-to-digital converters (ADCs) that digitize the output stream of the plurality of low pass filters (LPF), and
a digital signal processor (DSP) configured to filter one or more channels of the digitized output stream and compensate the one or more channels for in-phase quadrature (I/Q) imbalance.
16. The system of claim 15 , wherein the DSP further comprises:
a demultiplexer configured to contain a mapping from the plurality of ADCs to a plurality of RF channels.
17. The system of claim 16 , wherein the DSP further comprises:
an image rejection filter configured to estimate an in-phase quadrature (IQ) imbalance for each RF channel separately and to compensate for the IQ imbalance in the RF channel.
18. The system of claim 17 , wherein the DSP further comprises:
a channel selection filter configured to filter adjacent channels and interfering RF channels for each RF channel.
19. The system of claim 18 , wherein the DSP further comprises:
a down converter configured to convert the cable signal into a lower frequency.
20. The system of claim 19 , wherein the DSP further comprises:
a rate converter that converts the down-converted signal into a specified frequency for reception at a demodulator.