Front-end circuitry for a data receiver and related systems, methods, and devices
Front-end circuitry for a data receiver and related systems, methods, and devices are disclosed. The front-end circuitry includes a passive equalizer, which includes a signal input, an equalizer output including a first equalizer output and a second equalizer output, a first signal path, and a second signal path. The first signal path is between the signal input and the first equalizer output. The first signal path has a first frequency response. The second signal path is between the signal input and the second equalizer output. The second signal path has a second frequency response. The second frequency response exhibits substantially inverse behavior to that of the first frequency response. An amplifier circuit is configured to combine a first equalizer output signal from the first equalizer output with a second equalizer output signal from the second equalizer output to obtain an equalized output signal.
1. A passive equalizer, comprising:
a signal input;
an equalizer output including a first equalizer output and a second equalizer output;
a first signal path between the signal input and the first equalizer output, the first signal path having a first frequency response responsive to an input signal provided to the signal input; and
a second signal path between the signal input and the second equalizer output, the second signal path having a second frequency response responsive to the input signal provided to the signal input, the second frequency response exhibiting substantially inverse behavior to that of the first frequency response.
2. The passive equalizer of claim 1 , wherein the first signal path and the second signal path form respective portions of a Zobel network.
3. The passive equalizer of claim 2 , wherein the Zobel network is implemented as a balanced Zobel network.
4. The passive equalizer of claim 1 , wherein the first signal path and the second signal path include second order impedance networks.
5. The passive equalizer of claim 1 , comprising a bridge impedance bridging the first signal path with the second signal path.
6. The passive equalizer of claim 1 , wherein the first signal path and the second signal path are substantially free of bridging elements that bridge the first signal path and the second signal path.
7. The passive equalizer of claim 1 , wherein:
the first signal path includes a first impedance network comprising a first resistor in parallel with a series combination of a first capacitor with a first inductor; and
the second signal path includes a parallel combination of a second capacitor with a second inductor, the parallel combination of the second capacitor with the second inductor in series with a second resistor.
8. The passive equalizer of claim 1 :
the first equalizer output to provide a first equalizer output signal to a programmable amplifier circuit;
the second equalizer output to provide a second equalizer output signal to the programmable amplifier circuit; and
the programmable amplifier circuit to amplify and sum the first equalizer output signal and the second equalizer output signal to provide an equalized output signal.
9. Front-end circuitry for a data receiver, the front-end circuitry comprising:
a passive equalizer to receive an input signal, the passive equalizer including a first signal path and a second signal path, an impedance of the second signal path substantially the square of a reference impedance divided by an impedance of the first signal path, the first signal path to provide a first equalizer output signal responsive to the received input signal, the second signal path to provide a second equalizer output signal responsive to the received input signal; and
a programmable amplifier circuit to receive the first equalizer output signal and the second equalizer output signal from the passive equalizer, the programmable amplifier circuit comprising:
a first programmable-gain amplifier to amplify the first equalizer output signal with a first gain to provide a first amplified signal;
a second programmable-gain amplifier to amplify the second equalizer output signal with a second gain to provide a second amplified signal; and
a summing circuit to add the first amplified signal and the second amplified signal to provide an equalized output signal.
10. The front-end circuitry of claim 9 , wherein the second gain is equal to a difference between one and the first gain.
11. The front-end circuitry of claim 9 , wherein the programmable amplifier circuit comprises:
a first impedance matching network to terminate the first signal path; and
a second impedance matching network to terminate the second signal path.
12. The front-end circuitry of claim 9 , comprising a control circuitry to provide control signals to the programmable amplifier circuit to control the first gain and the second gain.
13. The front-end circuitry of claim 9 , wherein the programmable amplifier circuit comprises a programmable-gain summing amplifier.
14. The front-end circuitry of claim 9 , wherein the summing circuit comprises a linear summing amplifier.
15. The front-end circuitry of claim 9 , wherein at least one of the first programmable-gain amplifier and the second programmable-gain amplifier includes amplifier slices, each amplifier slice including a differential pair amplifier, gain adjustment of the at least one of the first programmable-gain amplifier and the second programmable-gain amplifier achieved by selectively turning the amplifier slices on or off.
16. A data receiver comprising front-end circuitry, the front-end circuitry comprising:
a passive equalizer to receive an input signal, the passive equalizer including a first signal path and a second signal path, an impedance of the second signal path substantially the square of a reference impedance divided by an impedance of the first signal path, the first signal path to provide a first equalizer output signal responsive to the received input signal, the second signal path to provide a second equalizer output signal responsive to the received input signal; and
a programmable amplifier circuit to receive the first equalizer output signal and the second equalizer output signal from the passive equalizer, the programmable amplifier circuit comprising:
a first programmable-gain amplifier to amplify the first equalizer output signal with a first gain to provide a first amplified signal;
a second programmable-gain amplifier to amplify the second equalizer output signal with a second gain to provide a second amplified signal; and
a summing circuit to add the first amplified signal and the second amplified signal to provide an equalized output signal.
17. The data receiver of claim 16 , wherein the data receiver is implemented as a serializer/deserializer.
18. The data receiver of claim 16 , comprising control circuitry to control the first gain of the first programmable-gain amplifier and the second gain of the second programmable-gain amplifier.
19. A method of equalizing an input signal, the method comprising:
generating a first equalizer output signal responsive to the input signal applied to a first signal path, the first signal path having a first frequency response;
generating a second equalizer output signal responsive to the input signal applied to a second signal path, the second signal path having a second frequency response, the second frequency response substantially inverse to the first frequency response;
amplifying the first equalizer output signal with a first gain to generate a first amplified signal;
amplifying the second equalizer output signal with a second gain to generate a second amplified signal; and
summing the first amplified signal with the second amplified signal to generate an equalized output signal.
20. The method of claim 19 , wherein generating the first equalizer output signal responsive to the input signal applied to the first signal path and generating the second equalizer output signal responsive to the input signal applied to the second signal path comprise applying the input signal to second-order impedance networks.
21. The method of claim 19 , wherein generating the second equalizer output signal responsive to the input signal applied to the second signal path comprises generating the second equalizer output signal responsive to the input signal applied to a second impedance that is dual to a first impedance of the first signal path.
22. The method of claim 19 , wherein amplifying the second equalizer output signal with the second gain comprises amplifying the second equalizer output signal with the second gain of one minus the first gain.
23. The method of claim 19 , wherein:
amplifying the first equalizer output signal comprises applying the first equalizer output signal to a first programmable-gain amplifier; and
amplifying the second equalizer output signal comprises applying the second equalizer output signal to a second programmable-gain amplifier.