Phased array antenna calibration using airborne radar clutter and MIMO

In active phased array radar systems, beamformer performance will be degraded by unknown phase and gain deviations across the antenna array. Elements within the array can be calibrated by injecting a known signal directly into each receiver module (e.g., via a loop-back path, or via mutual coupling), but this approach does not correct transmission or array deformation errors. Fortunately, when the radar system is airborne, an alternative approach for removing array errors can be used. This approach uses radar clutter to calibrate the radar while in flight. An antenna calibration algorithm that removes transmit and receive subarray errors, using MIMO (Multiple Input, Multiple Output) waveforms, is described and simulated.