An electronically-implemented method of an antenna array calibration comprising: determining a first near-field amplitude relationship for a first calibration group using a first probe of an antenna array , wherein the first calibration group comprises at least a first antenna element of the antenna array and a second antenna element of the antenna array, and the first probe is disposed symmetrically between the first antenna element and the second antenna element; determining a first near-field phase relationship between at least the first antenna element and the second antenna element using the first probe; storing the first near-field amplitude relationship and the first near-field phase relationship as calibration data for the antenna array; characterised by further comprising: determining a second near-field amplitude relationship for a second calibration group using a second probe of the antenna array, wherein the second calibration group comprises at least the second antenna element and a third antenna element of the antenna array, and the second probe is disposed symmetrically between the second antenna element and the third antenna element; determining a second near-field phase relationship between at least the second antenna element and the third antenna element using the second probe; and storing the second near-field amplitude relationship and the second near-field phase relationship as calibration data for the antenna array. determining a first near-field amplitude relationship for a first calibration group using a first probe of an antenna array , wherein the first calibration group comprises at least a first antenna element of the antenna array and a second antenna element of the antenna array, and the first probe is disposed symmetrically between the first antenna element and the second antenna element; determining a first near-field phase relationship between at least the first antenna element and the second antenna element using the first probe; storing the first near-field amplitude relationship and the first near-field phase relationship as calibration data for the antenna array; characterised by further comprising: determining a second near-field amplitude relationship for a second calibration group using a second probe of the antenna array, wherein the second calibration group comprises at least the second antenna element and a third antenna element of the antenna array, and the second probe is disposed symmetrically between the second antenna element and the third antenna element; determining a second near-field phase relationship between at least the second antenna element and the third antenna element using the second probe; and storing the second near-field amplitude relationship and the second near-field phase relationship as calibration data for the antenna array. determining a second near-field amplitude relationship for a second calibration group using a second probe of the antenna array, wherein the second calibration group comprises at least the second antenna element and a third antenna element of the antenna array, and the second probe is disposed symmetrically between the second antenna element and the third antenna element; determining a second near-field phase relationship between at least the second antenna element and the third antenna element using the second probe; and storing the second near-field amplitude relationship and the second near-field phase relationship as calibration data for the antenna array. <EOS>