On Uncertainty Investigation of mmWave Phased-Array Element Control with an All-On Method

Accurate control of complex excitation of array elements is key to ensure spatial discrimination capability of millimeter-wave (mmWave) phased array, e.g., beamforming to target signal directions and nulling toward interference signal directions. Element excitation uncertainties are typically evaluated in an 'on-off' mode, where the element under test is enabled with other phased-array elements properly terminated. However, such an 'on-off' method might lead to inaccurate results due to the fact that mmWave phased arrays are typically designed for an 'all-on' mode, where all array elements are enabled with proper complex excitations. Therefore, there is a need to accurately determine the array element excitation uncertainties in its typical operation mode, i.e., 'all-on' mode. In this letter, an 'all-on' method is proposed to enable accurate array element uncertainty investigation in the 'all-on' mode. The proposed algorithm is experimentally validated in a 4 × 4 mmWave phased-array experimental platform. The experimental results have shown that an amplitude deviation up to \pm0.1 dB and a phase deviation \pm \text{1}^\circ can be achieved in the 'all-on' mode with the proposed method, compared to those up to \pm0.8 dB and \pm \text{9}^\circ, respectively, for the conventional 'on-off' method.