Method and apparatus for antenna array calibration using on-board receiver

A feedback processor for use with an antenna array, the feedback processor configured to receive outbound signals at the antenna array, the antenna array having a plurality of antennas, the feedback processor comprising:

• a plurality of inputs, each input configured to receive an outbound signal of a plurality of outbound signals separately transmitted to a corresponding antenna of the plurality of antennas;
• a radio frequency to baseband converter configured to convert the plurality of outbound signals to a corresponding plurality of baseband signals;
• a parallel to serial converter configured to serialize the corresponding plurality of parallel baseband signals into a serial feedback signal;
• and
• a serial to parallel converter configured to convert the serial feedback signal into a plurality of parallel feedback signals, each parallel feedback signal corresponding to one of the derived feedback signals from the plurality of outbound signals.

A calibration method to compensate for signal impairment in a plurality of separate transmit paths, the transmitter having a radio unit configured to receive outbound signals and transmit the outbound signals to an antenna array via a separate transmit path for each outbound signal, the antenna array including a feedback processor, the method comprising:

• receiving at the antenna array, a plurality of the outbound signals after each outbound signal traverses a respective separate transmit path;
• deriving a plurality of feedback signals from the corresponding received outbound signals;
• serializing the plurality of feedback signals into a serial feedback signal;
• transmitting the serial feedback signal from the feedback processor to the radio unit;
• and
• converting, at the radio unit, the serial feedback signal into a plurality of parallel feedback signals, each parallel feedback signal corresponding to one of the derived feedback signals from the plurality of outbound signals;
• and
• for each transmit path:
• capturing an outbound signal received by the transmitter as a reference signal before the outbound signal is input to a transmit path of the radio unit;
• computing an impairment value of the transmit path of the corresponding outbound signal based on the corresponding reference signal and a corresponding parallel feedback signal;
• and
• correcting an impairment of the transmit path by applying the impairment value to the outbound signal before the outbound signal traverses the transmit path.

A radio configured to compensate for signal impairment in separate transmit paths of the transmitter and to drive an antenna array, the radio comprising:

• a feedback processor coupled to ports of the antenna array and configured to:
• derive a plurality of feedback signals from outbound signals that have traversed their respective separate transmit paths;
• serialize the plurality of feedback signals into a serial feedback signal
• transmit the serial feedback signal from the feedback processor to a radio unit;
• and
• a radio unit configured to:
• receive a plurality of outbound signals;
• route the plurality of outbound signals to the transmit paths;
• capture the outbound signals before the outbound signals are submitted to the transmit paths to provide reference signals corresponding to the transmit paths;
• receive the serial feedback signal from the feedback processor;
• convert the serial feedback signals to a plurality of parallel feedback signals, each parallel feedback signal corresponding to a derived feedback signal from the plurality of outbound signals;
• and
• for each transmit path:
• compute an impairment value for each transmit path based on a parallel feedback signal corresponding to the path and a reference signal corresponding to the path;
• and
• correct an impairment of each transmit path by applying the impairment value for the transmit path to an outbound signal before the outbound signal traverses the transmit path.