Communication system, apparatus and methods for calibrating an antenna array

A method for calibrating an antenna array comprising a plurality of antenna elements coupled to a plurality of respective transmit paths in a wireless communication system, the method comprising in transmit mode the steps of:

• routing live transmit network signals through at least one transmit path;
• feeding back a portion of the live transmit signals pertaining to a selected path under calibration measurement via a switched coupler network thereby transforming the transmit live network signal to a feedback digital IQ signal;
• running a transmit calibration measurement routine on at least one processor configured to determine at least one measurement value used to calibrate the individual single transmit path and waiting for at least one converged measurement value of at least one from a group consisting of:
• amplitude, phase or latency;
• wherein the calibration measurement comprises a comparison of an adapted IQ data stream pertaining to the live network transmit signals and the feedback digital IQ signal to determine said at least one converged measurement value;
• extracting the converged measurement value of at least one individual single transmit path;
• repeating steps of applying, running, and extracting for a next individual single transmit path until the calibration routine has completed;
• selecting a converged measurement value of at least one individual single transmit path from a plurality of transmit paths to form a reference transmitter calibration measurement result;
• normalizing a plurality of at least one measurement values of a plurality of transmit paths using the reference transmitter calibration measurement result;
• selecting one of the plurality of normalized measurement values based on prescribed criteria;
• and
• applying a selected normalized measurement value to at least one of the plurality of transmit paths.

A network element for calibrating an antenna array comprising a plurality of antenna elements coupled to a plurality of respective receive paths in a wireless communication system, wherein the network element comprises, in receive mode:

• a plurality of independent receiver circuits coupled to respective antenna elements of the antenna array;
• a circuit for translating first digital IQ signals to a radio frequency to generate a receive test signal and apply the received test signal to a switched coupler array network so that the receive test signal is substantially coupled only to an individual single receive path of the plurality of receive paths to transform the received test signal to a feedback digital IQ signal;
• a selector arranged to select the feedback digital IQ signal;
• at least one processor configured for executing the steps of:
• running a receive calibration measurement routine using the first digital IQ signals to determine at least one measurement value of at least amplitude, phase or latency and waiting for at least one converged measurement value, wherein the calibration measurement comprises a comparison of an adapted digital IQ signal and the selected feedback digital IQ signal on an output of the individual single receive path to determine said at least one converged measurement value;
• arranging to extract the converged at least one measurement value for the at least one individual receive path;
• repeating operations of applying, running, and extracting for a next individual single receive path until the calibration measurement routine has completed;
• selecting a converged measurement value of at least one individual receive path from a plurality of receive paths to form a reference receiver calibration result;
• normalizing a plurality of at least one measurement values of the plurality of receive paths using the reference receiver calibration result;
• and
• applying the at least one composite beam weighting coefficient to respective receive paths.

A network element for calibrating an antenna array comprising a plurality of antenna elements coupled to a plurality of respective transmit paths in a wireless communication system, wherein the network element comprises, in transmit mode:

• a plurality of independent transmit circuits coupled to respective antenna elements of the antenna array;
• a switched coupler network arranged to feed back a portion of the live transmit network signals pertaining to a selected path under calibration measurement thereby transforming the transmit live network signal to a feedback digital IQ signal;
• at least one processor configured for routing live transmit network signals through least one transmit path and executing the steps of;
• running a transmit calibration routine to determine at least one measurement value used to calibrate the individual single transmit path and waiting for at least one converged measurement value of at least one from a group consisting of:
• amplitude, phase or latency;
• wherein the calibration measurement comprises a comparison of an adapted IQ data stream pertaining to the live network transmit signals and the feedback digital IQ signal to determine said at least one converged measurement value;
• extracting the converged at least one measurement value of at least one individual single transmit path;
• repeating the steps of applying, running, extracting for a next individual single transmit path until the calibration routine has completed;
• selecting a converged measurement value of at least one individual single transmit path from a plurality of transmit paths to form a reference transmitter calibration measurement result;
• normalizing a plurality of at least one measurement values of a plurality of transmit paths using the reference transmitter calibration result;
• selecting one of the plurality of normalized measurement values based on prescribed criteria;
• and
• applying the normalized measurement value to at least one of the plurality of transmit paths.