Adaptive beamforming using calibration vectors with unknown gain and phase

The importance of taking the direction dependent amplitude and phase of the received signals (due to the mutual coupling) into account in the calibration is demonstrated using adaptive beamforming (Capon´s method). The method is compared to a direction dependent (local) calibration method, which is shown to be the preferred method if there are position errors in the array. In reality, robust versions of Capon´s method is always used. The calibration is considered as a complement to these robust methods, to reduce the array steering vector errors and thereby further improve the performance of the robust Capon methods. The calibration also allows for larger errors in the array, which translates to a potential to decrease the manufacturing cost.