Internal reflection cancellation for multi-port full duplex node and amplifier

An internal reflection cancelling full duplex node comprising:

• a first downstream splitter with an input coupled to a primary downstream line, a first output coupled to a first downstream line and a second output coupled to a second downstream line;
• a second downstream splitter with an input coupled to the second downstream line, a first output coupled to a third downstream line and a second output coupled to a fourth downstream line;
• a first bidirectional line coupled to a first port;
• a second bidirectional line coupled to a second port;
• a third bidirectional line coupled to a third port;
• a first upstream splitter with an input coupled to the first port, a first output coupled to the first downstream line and a second output coupled to a first upstream line;
• a second upstream splitter with an input coupled to the second port, a first output coupled to the third downstream line and a second output coupled to a second upstream line;
• a third upstream splitter with an input coupled to the third port, a first output coupled to the fourth downstream line and a second output coupled to a third upstream line;
• a first upstream combiner with a first input coupled to the first upstream line, a second input coupled to a fourth upstream line and an output coupled to a primary upstream line;
• and
• a second upstream combiner with a first input coupled to the second upstream line, a second input coupled to the third upstream line and an output coupled to the fourth upstream line.

An internal reflection cancelling full duplex node comprising:

• a downstream splitter with an input coupled to a primary downstream line, a first output coupled to a first downstream line, a second output coupled to a second downstream line, a third output coupled to a third downstream line, and a fourth output coupled to a fourth downstream line;
• a first bidirectional line coupled to a first port;
• a second bidirectional line coupled to a second port;
• a third bidirectional line coupled to a third port;
• a fourth bidirectional line coupled to a fourth port;
• a first upstream splitter with an input coupled to the first port, a first output coupled to the first downstream line and a second output coupled to a first upstream line;
• a second upstream splitter with an input coupled to the second port, a first output coupled to the second downstream line and a second output coupled to a second upstream line;
• a third upstream splitter with an input coupled to the third port, a first output coupled to the third downstream line and a second output coupled to a third upstream line;
• a fourth upstream splitter with an input coupled to the fourth port, a first output coupled to the fourth downstream line and a second output coupled to a fourth upstream line;
• a first upstream combiner with a first input coupled to the first upstream line, a second input coupled to the second upstream line and an output coupled to a first combined line;
• a second upstream combiner with a first input coupled to the third upstream line, a second input coupled to the fourth upstream line and an output coupled to a second combined line;
• and
• a third upstream combiner with a first input coupled to the first combined line, a second input coupled to the second combined line and an output coupled to a primary upstream line.

A method for internal reflection cancelling in full duplex node comprising the steps of:

• splitting, in a downstream splitter, a downstream signal equally into a first split of the downstream signal and a second split of the downstream signal;
• transmitting the first split of the downstream signal through a first upstream splitter to a first port;
• transmitting the second split of the downstream signal through a second upstream splitter to a second port;
• passing a reflection of the first split of the downstream signal through the first upstream splitter to an upstream combiner;
• passing a reflection of the second split of the downstream signal through the second upstream splitter to the upstream combiner;
• wherein a first signal path from the downstream splitter to the first port back through the first upstream splitter to the upstream combiner has a path length and propagation characteristics that are identical to a second signal path from the downstream splitter to the second port back through the second upstream splitter to the upstream combiner;
• inducing, in the upstream combiner, a 180 degree relative phase shift between the reflection of the first split of the downstream signal and the reflection of the second split of the downstream signal;
• and
• combining, in the upstream combiner, the reflection of the first split of the downstream signal and of the reflection of the second split of the downstream signal.