Apparatus, method, computer program for calibrating an array of dual-polarized antenna elements

An apparatus comprising:

• an array of dual-polarized antenna elements wherein each dual-polarized antenna element comprises:
• a pair of orthogonal polarization feeds, and
• a coupler configured to couple, in the near field, the orthogonal polarizations;
• control circuitry configured to control, for each polarization, for each dual-polarized antenna element, a power adjustment and/or a phase adjustment applied to signals of the respective polarization feeds of the respective dual-polarized antenna element;
• measurement circuitry configured to measure, for each polarization, for each dual-polarized antenna element via its respective coupler, a power and/or a phase of a signal transmitted from the respective dual-polarized antenna array;
• and
• calibration circuitry configured to calibrate the control circuitry, wherein the calibration circuitry is configured to adjust, for each polarization, for each dual-polarized antenna element, the power adjustment and/or the phase adjustment applied to signals of the respective polarization feeds of the respective dual-polarized antenna element in dependence upon the measurement, for each polarization, of power and/or phase of the signal transmitted from the respective dual-polarized antenna element, wherein:
• (i) a coupling between respective dual-polarized antenna elements of the array is configured based upon modifications to test the power adjustment and/or the phase adjustment applied to signals of the respective polarization feeds of the respective dual-polarized antenna element,
• (ii) the coupling is configured based upon modifications attributable to applying a jamming signal using a jamming antenna of the array of dual-polarized antenna elements, responsive to a user equipment (UE) being scheduled for Sounding Reference Signals (SRS) transmission,
• (iii) a power level of the jamming signal is dependent on a configured power level at the UE and a distance between the jamming antenna and the UE, and
• (iv) the control circuitry, the measurement circuitry and the calibration circuitry form a closed control loop that is configured to iterate to continually improve a similarity between the measured power or measured phase at transmission to an expected value of power or an expected value of phase at transmission for a particular beam direction associated with the signal transmitted from the respective dual-polarized antenna array until the similarity satisfies a threshold.