Serdes transmitter and receiver utilizing single frequency phase amplitude modulation
Multiple examples are disclosed of SerDes transmitters and receivers. In one example, a transmitter comprises a mapping block to receive a clock signal and a two-bit data signal and to generate a plurality of pairs of digital values; a plurality of current steering blocks, each of the plurality of current steering blocks receiving one of the plurality of pairs of digital values to generate a pair of currents; a current summer and modulation block to receive the pair of currents from each of the plurality of current steering blocks to generate a differential output signal; wherein the differential output signal is a single frequency pulse amplitude modulated signal wherein the single frequency is a frequency of the clock signal.
1 . A transmitter comprising:
a mapping block to receive a clock signal and a two-bit data signal and to generate a plurality of pairs of digital values;
a plurality of current steering blocks, each of the plurality of current steering blocks receiving one of the plurality of pairs of digital values to generate a pair of currents;
a current summer and modulation block to receive the pair of currents from each of the plurality of current steering blocks to generate a differential output signal;
wherein the differential output signal is a single frequency pulse amplitude modulated signal wherein the single frequency is a frequency of the clock signal.
2 . The transmitter of claim 1 , wherein the differential output signal transmits a first bit of the two-bit signal when the clock signal is high.
3 . The transmitter of claim 2 , wherein the differential output signal transmits a second bit of the two-bit signal when the clock signal is low.
4 . The transmitter of claim 1 , wherein the mapping block further receives a valid signal indicating the two-bit data signal is to be transmitted.
5 . A receiver comprising:
a demodulation and amplifier block to receive a differential signal and to generate a plurality of pairs of currents;
a plurality of comparator and calibration blocks, each of the plurality of comparator and calibration blocks receiving one of the plurality of pairs of currents to generate a comparator output; and
a demapping block to receive the comparator output from each of the plurality of comparator and calibration blocks to generate a clock signal and a two-bit data signal.
6 . The receiver of claim 5 , wherein each of the plurality of comparator and calibration blocks engages in a calibration mode in response to the differential signal.
7 . The receiver of claim 6 , wherein during the calibration mode, a first input to a digital-to-analog converter in the comparator and calibration block is varied until an output of the digital-to-analog converter matches a first value in the differential signal.
8 . The receiver of claim 7 , wherein during the calibration mode, a second input to a digital-to-analog converter in the comparator and calibration block is varied until an output of the digital-to-analog converter matches a second value in the differential signal.
9 . The receiver of claim 8 , wherein during an operation mode, the first input and the second input are applied to the digital-to-analog converter to generate a first current and a second current used to generate the comparator output.
10 . The receiver of claim 5 , wherein the demapping block further generates a valid signal indicating the two-bit data signal contains valid data.
11 . A system comprising:
a transmitter comprising:
a mapping block to receive a clock signal and a two-bit data signal and to generate a plurality of pairs of digital values;
a plurality of current steering blocks, each of the plurality of current steering blocks receiving one of the plurality of pairs of digital values to generate a pair of currents;
a current summer and modulation block to receive the pair of currents from each of the plurality of current steering blocks to generate a differential output signal;
wherein the differential output signal is a single frequency pulse amplitude modulated signal wherein the single frequency is a frequency of the clock signal;
a receiver comprising:
a demodulation and amplifier block to receive a differential signal and to generate a plurality of pairs of currents;
a plurality of comparator and calibration blocks, each of the plurality of comparator and calibration blocks receiving one of the plurality of pairs of currents to generate a comparator output; and
a demapping block to receive the comparator output from each of the plurality of comparator and calibration blocks to generate the clock signal and the two-bit data signal; and
an interface coupling the transmitter and the receiver.
12 . The system of claim 11 , wherein the differential output signal transmits a first bit of the two-bit signal when the clock signal is high.
13 . The system of claim 12 , wherein the differential output signal transmits a second bit of the two-bit signal when the clock signal is low.
14 . The system of claim 11 , wherein the mapping block further receives a valid signal indicating the two-bit data signal is to be transmitted and the demapping block further generates a valid signal indicating the two-bit data signal contains valid data.
15 . The system of claim 11 , wherein each of the plurality of comparator and calibration blocks engages in a calibration mode in response to the differential signal.
16 . The system of claim 15 , wherein during the calibration mode, a first input to a digital-to-analog converter in the comparator and calibration block is varied until an output of the digital-to-analog converter matches a first value in the differential signal.
17 . The system of claim 16 , wherein during the calibration mode, a second input to a digital-to-analog converter in the comparator and calibration block is varied until an output of the digital-to-analog converter matches a second value in the differential signal.
18 . The system of claim 17 , wherein during an operation mode, the first input and the second input are applied to the digital-to-analog converter to generate a first current and a second current used to generate the comparator output.
19 . The system of claim 11 , wherein the transmitter and the receiver maintain a constant DC current over the interface.
20 . A method comprising:
generating, by a transmitter, a differential signal in response to a clock signal and a two-bit data signal wherein the differential signal is a single frequency pulse amplitude modulated signal and wherein the single frequency is a frequency of the clock signal;
receiving, by a receiver, the differential signal; and
generating, by the receiver, the clock signal and the two-bit data signal in response to the differential signal.