Full duplex DOCSIS amplifier with legacy upstream support

1 . An amplifier circuit comprising:

a northbound port and a southbound port, each propagating a full duplex (FDX) signal having a first frequency band that includes both an FDX upstream signal and a downstream FDX signal, and each propagating a legacy upstream signal in a second frequency band that is free from including a downstream signal; and

a power amplifier that simultaneously amplifies the FDX upstream signal and the legacy upstream signal,

at least one electrical component that isolates the FDX upstream signal from the legacy upstream signal;

wherein the FDX upstream signal is processed by a signal processing unit after isolation from said legacy upstream signal and said FDX upstream signal is processed differently than said legacy upstream signal; and

the FDX upstream signal and the legacy upstream signal are simultaneously amplified after said FDX upstream signal is processed differently than said legacy upstream signal.

2 . The amplifier circuit of claim 1 , wherein the signal processing unit performs at least one of echo cancellation and digital predistortion.

3 . The amplifier circuit of claim 1 including a preamplifier that amplifies the legacy upstream signal but does not amplify the FDX upstream signal.

4 . The amplifier circuit of claim 1 including a second power amplifier that amplifies the downstream FDX signal.

5 . The amplifier circuit of claim 4 including at least one electrical component that isolates the FDX downstream signal from the legacy upstream signal.

6 . The amplifier circuit of claim 1 including an FDX coupler at the southbound port having a low-loss port and a coupled port, where the power amplifier is positioned between the low-loss port and an FDX coupler at the northbound port.

7 . The amplifier circuit of claim 6 where the coupled port is connected to an upstream input of the signal processing unit.

8 . The amplifier circuit of claim 7 including at least one electrical component that isolates the FDX downstream signal from the legacy upstream signal.

9 . The amplifier circuit of claim 8 where the at least one electrical component is located between the coupled port and the upstream input of the signal processing unit.

10 . The amplifier circuit of claim 8 where the at least one electrical component is located between a high-loss port of the coupled port and the upstream input of the signal processing unit.

11 . The amplifier circuit of claim 1 that also propagates a downstream signal in a third frequency band.

12 . The method of claim 1 including isolating the FDX downstream signal from the legacy upstream signal.

13 . A method comprising:

receiving at an full duplex (FDX) amplifier circuit a full duplex downstream signal and a full duplex upstream signal that together share a first frequency band;

receiving at the FDX amplifier a legacy upstream signal in a second frequency band that is free from including a downstream signal;

isolating the full duplex upstream signal from the legacy upstream signal;

after isolating the full duplex upstream signal processing in a signal processing unit the full duplex upstream signal differently than said legacy upstream signal; and

simultaneously amplifying a combined signal that includes both the full duplex upstream signal and the legacy upstream signals;

wherein the full duplex upstream signal and the legacy upstream signal are simultaneously amplified after processing the full duplex upstream signal differently than said legacy upstream signal.

14 . The method of claim 13 including performing at least one of echo cancellation and digital predistortion in the signal processing unit.

15 . The method of claim 13 including pre-amplifying the legacy upstream signal but without pre-amplifying the FDX upstream signal.

16 . The method of claim 13 including amplifying the downstream FDX signal.