Isolation of transmit and receive signals in full-duplex communication systems

A method for isolating a transmit port and a receive port to maintain a desired level of electrical isolation between a signal on the transmit port and an incoming signal received on the receive port in a shared channel environment, the method comprising:

• receiving an incoming signal at a channel node from a channel;
• providing an outgoing signal to a transmit port;
• processing the incoming signal to thereby attenuate lower frequency portions of the incoming signal and amplify higher frequency portions of the incoming signal, to thereby create a processed incoming signal;
• processing the outgoing signal to generate two or more generally equal outgoing signals;
• providing the processed incoming signal and the incoming signal to a summing device;
• and
• providing the two or more generally equally processed outgoing signal to a summing device, wherein the generally equal outgoing signals cancel in the summing device and the summing device outputs the incoming signal.

A isolation circuit comprising:

• a channel port;
• a transmit port;
• a receive port;
• a first filter connected to the channel port;
• a second filter;
• a signal source connected to the transmit port, the first filter, and the second filter;
• and
• a summing junction connected to the receive port, the channel port, and the second filter.

A signal isolation unit comprising:

• a channel port configured to connect to a channel;
• a transmit port configured to connect to a transmitter;
• a receive port configured to connect to a receiver;
• a differencing amplifier comprising:
• an output connected to the receiver port
• a first input connected to the channel port;
• a second input connected to a second filter;
• a current-mode driver comprising an input connected to the transmit port and an output connected to the first filter and a second filter;
• wherein the first filter connects to the channel port and the first filter and the second filter have generally similar transfer functions.

A isolation circuit comprising:

• a first port configured to connect to a channel;
• a second port configured to connect to a transmitter;
• a third port configured to connect to a receiver;
• at least one filter configured to:
• filter a received signal traveling from the channel to the receive port;
• and
• filter a transmitted signal traveling from the second port to the channel, wherein the isolation circuit is configured to isolate the received signal while rejecting the transmitted signal from the third port.