Methods and systems for interference mitigation in a dual-polarized communication system

An interference mitigation apparatus, comprising:

• an adaptive feedforward filtering stage and an adaptive feedback filtering stage configured to produce a plurality of output signals from a plurality of frequency downconverted signals, the output signals for being provided to a data decoding stage;
• a plurality of phase rotators configured to apply phase rotation to the frequency downconverted signals prior to processing by the adaptive feedforward filtering stage and the adaptive feedback filtering stage;
• and
• an adaptive controller configured for varying an amount of the phase rotation applied by the phase rotators to the frequency downconverted signals based at least in part on symbol decisions made on the output signals;
• a time invariant feed-forward filter applied to the frequency downconverted signals before processing by the phase rotators.

A communication system, comprising:

• a transmitter configured to send a plurality of orthogonally polarized signals containing transmit data using faster-than-Nyquist transmission;
• a receiver comprising a plurality of orthogonally polarized antennas to produce a corresponding plurality of received signals from a composite received version of the polarized signals, the receiver configured to process each of the received signals by applying adaptively controlled amounts of phase rotation;
• processing with an adaptive feedforward filtering stage;
• and processing with an adaptive feedback stage to obtain output signals, whereby the output signals are decoded by a data decoding stage to obtain estimates of the transmit data.

An interference mitigation apparatus, comprising:

• an inter-symbol-interference (ISI) mitigation portion with a plurality of inputs and a plurality of outputs, the inputs for receiving corresponding demodulated signals of respective polarizations;
• a cross-polarization interference (XPI) mitigation portion with a plurality of inputs and a plurality of outputs, the inputs being connected respectively to the outputs of the ISI mitigation portion, the outputs of the XPI mitigation portion for being provided to a data decoding stage;
• and
• a plurality of phase rotators for phase rotating the demodulated signals provided to the inputs of the ISI mitigation portion, the phase rotators being adaptively controlled based at least in part on symbol decisions made on the outputs of the XPI mitigation portion.