Network transceiver with VGA channel specific equalization
A network transceiver device is provided, including at least two variable gain amplifiers (VGAs), and at least two sets of analog digital converters (ADCs), each set including ADCs coupled to an output of one of the VGAs, the sets being arranged in VGA-specific channels. The device includes a plurality of feed-forward equalizers (FFEs), each FFE being coupled to receive an output of one of the ADCs in one of the VGA-specific channels. Each FFE is configured to adaptively equalize the output received from the ADCs utilizing a first equalization coefficient subset with coefficient values that are common to all FFEs, and a second equalization coefficient subset that is channel specific and that has a first set of coefficient values for a first VGA-specific channel and a second set of coefficient values for a second VGA-specific channel, the sets of coefficient values being computed independently.
1 . A network transceiver device, comprising:
a plurality of variable gain amplifiers (VGAs) configured to amplify received signals;
at least two sets of analog digital converters (ADCs), each set including a plurality of ADCs coupled to a respective output of a corresponding one of the plurality of VGAs, wherein a first set of the at least two sets of ADCs is arranged in at least a first VGA-specific channel and a second set of the at least two sets of ADCs is arranged in at least a second VGA-specific channel; and
a clock data recovery (CDR) circuit coupled to each of the plurality of ADCs, wherein the CDR circuit is configured to receive an ADC sample signal from each of the plurality of ADCs, and in response is configured to generate a channel timing signal and an ADC timing signal, the channel timing signal alternating between the first VGA-specific channel and the second VGA specific channel, and the ADC timing signal including pulses that increment through each of the plurality of ADCs in each set of the at least two sets of ADCs.
2 . The network transceiver device of claim 1 , wherein
the CDR circuit includes a phase detector configured to detect a phase of a signal received from each of the plurality of ADCs.
3 . The network transceiver device of claim 2 , further comprising:
the phase detector of the CDR circuit is configured to determine a timing of an impulse response in the received signal from each of the plurality of ADCs utilizing at least two precursor coefficients, a main coefficient, and at least two post cursor coefficients.
4 . The network transceiver device of claim 1 , wherein the CDR circuit is configured to correct skew among samples from the ADCs taking into consideration both pre-cursor and post-cursor timing errors in order to correct the sample skew.
5 . The network transceiver device of claim 4 , wherein the CDR circuit operates in either a differential timing mode or a common timing mode.
6 . The network transceiver device of claim 5 , wherein, in the differential timing mode, differences in the timing among each ADC in a particular VGA-specific channel within each of the at least two sets of ADCs are corrected.
7 . The network transceiver device of claim 5 , in the common timing mode, differences between the at least two sets of ADCs are corrected.
8 . The network transceiver device of claim 1 ,
wherein the network transceiver device is configured to operate as a four-level pulse-amplitude modulated (PAM-4) transceiver.
9 . A signal processing method, comprising:
amplifying received signals at a plurality of variable gain amplifiers (VGAs);
receiving amplified signals from the plurality of VGAs at each set of at least two sets of analog digital converters (ADCs), each set including a plurality of ADCs coupled to a respective output of a corresponding one of the plurality of VGAs, wherein a first set of the at least two sets of ADCs is arranged in at least a first VGA-specific channel and a second set of the at least two sets of ADCs is arranged in at least a second VGA-specific channel; and
receiving an ADC sample signal from each of the plurality of ADCs at a clock data recovery (CDR) circuit coupled to each of the plurality of ADCs, and in response, generating a channel timing signal and an ADC timing signal, the channel timing signal alternating between the first VGA-specific channel and the second VGA specific channel, and the ADC timing signal including pulses that increment through each of the plurality of ADCs in each set of the at least two sets of ADCs.
10 . The signal processing method of claim 9 , wherein
the CDR circuit includes a phase detector configured to detect a phase of a signal received from each of the plurality of ADCs.
11 . The signal processing method of claim 10 , further comprising:
determining a timing of an impulse response in the received signal from each ADC utilizing at least two precursor coefficients, a main coefficient, and at least two post cursor coefficients, using the phase detector of the CDR circuit.
12 . The signal processing method of claim 9 , further comprising:
correcting, via the CDR circuit, skew among samples from the ADCs taking into consideration both pre-cursor and post-cursor timing errors in order to correct sample skew.
13 . The signal processing method of claim 12 , wherein the CDR circuit operates in either a differential timing mode or a common timing mode.
14 . The signal processing method of claim 13 , wherein, in the differential timing mode, differences in the timing among each ADC in a particular VGA-specific channel within each of the at least two sets of ADCs are corrected.
15 . The signal processing method of claim 13 , in the common timing mode, differences between the at least two sets of ADCs are corrected.
16 . The signal processing method of claim 9 , further comprising:
equalizing the output of the plurality of ADCs, to generate an equalized digital signal.
17 . The signal processing method of claim 16 , further comprising outputting data including a PAM-4 symbol or data contained within a PAM-4 symbol, based on the equalized digital signal.