Active resistive summer for a transformer hybrid

• US 8,880,017 B1
• Filed: 08/05/2013
• Issued: 11/04/2014
• Est. Priority Date: 07/31/2000
• Status: Expired due to Term

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Roo, Pierte, Sutardja, Sehat
• Primary Examiner(s): Yun, Eugene
• Application Number:
  US13/958,915
• Time in Patent Office: 456 Days
• Field of Search: 455/296, 455/295, 455/278.1, 455/63.1, 455/67.13, 455/570, 455/301, 370/286, 370/289
• US Class Current: 455/296
• CPC Class Codes: H04B 1/581 using a transformer
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end

Abstract

A system includes a transceiver configured to receive a composite signal. The composite signal is a composite of a transmit signal and a receive signal. A replica transmitter is configured to generate a replica transmit signal based on the transmit signal. A transmit canceller is configured to recover the receive signal at least in part by resistively summing the composite signal and the replica transmit signal.

Claims

1. A system, comprising:

a transmitter configured to i) receive a first signal to be transmitted by the transmitter via a communications channel, ii) receive a second signal via the communications channel, and iii) generate a composite signal corresponding to a combination of the first signal and the second signal;

a replica transmitter configured to generate, based on the first signal to be transmitted by the transmitter, a replica transmit signal;

a baseline wander correction module configured to generate a control current to correct a baseline wander, wherein the baseline wander corresponds to a deviation from an initial DC potential of at least one of the first signal and the second signal; and

a transmit canceller configured to i) generate a receive signal based on the second signal received via the communications channel, ii) subtract the replica transmit signal from the composite signal, and iii) add the control current to the composite signal.

2. The system of claim 1, wherein the transmit canceller includes an active resistive summer.

3. The system of claim 2, wherein the active resistive summer sums the composite signal, the replica transmit signal, and the control current.

4. The system of claim 2, wherein the active resistive summer includes an operational amplifier, and wherein the composite signal, the replica transmit signal, and the control current are directly connected together at an inverting input of the operational amplifier.

5. The system of claim 4, wherein the active resistive summer includes a feedback resistor connected to i) an output of the operational amplifier, and ii) the inverting input of the operational amplifier.

6. The system of claim 4, wherein a common-mode shift current is directly connected to the inverting input of the operational amplifier.

7. The system of claim 6, wherein the common-mode shift current is based on a desired output common-mode voltage of the operational amplifier, a transconductance of the operational amplifier, and a current offset.

8. The system of claim 7, further comprising a voltage controlled current source configured to generate the common-mode shift current to cause the operational amplifier to generate the desired output common-mode voltage.

9. A method, comprising:

receiving a first signal to be transmitted by a transmitter via a communications channel;

receiving a second signal via the communications channel;

generating a composite signal corresponding to a combination of the first signal and the second signal;

generating, based on the first signal to be transmitted by the transmitter, a replica transmit signal;

generating a control current to correct a baseline wander, wherein the baseline wander corresponds to a deviation from an initial DC potential of at least one of the first signal and the second signal; and

to generate a receive signal based on the second signal received via the communications channel, subtracting the replica transmit signal from the composite signal, and adding the control current to the composite signal.

10. The method of claim 9, further comprising using an active resistive summer to subtract the replica transmit signal from the composite signal and add the control current to the composite signal.

11. The method of claim 10, further comprising using the active resistive summer to sum the composite signal, the replica transmit signal, and the control current.

12. The method of claim 10, wherein the active resistive summer includes an operational amplifier, and further comprising directly connecting the composite signal, the replica transmit signal, and the control current together at an inverting input of the operational amplifier.

13. The method of claim 12, further comprising directly connecting a common-mode shift current to the inverting input of the operational amplifier.

14. The method of claim 13, wherein the common-mode shift current is based on a desired output common-mode voltage of the operational amplifier, a transconductance of the operational amplifier, and a current offset.

15. The method of claim 14, further comprising generating the common-mode shift current to cause the operational amplifier to generate the desired output common-mode voltage.