Active array self calibration

A process and a method are disclosed for collecting phase and amplitude calibration data for an active array system (50) without the use of external sensors. The relative phase and amplitudes of adjacent T/R modules are determined when viewed through the entire array system (50). The calibration process involves collecting and storing these phases and amplitudes for future use. A pulse-to-pulse phase or amplitude modulation mode is employed. An element (62A-62F) is commanded into this mode to separate its signal (in frequency) from competing signals and leakages from the surrounding modules (62A-62F). A T/R inversion command allows for a single element (62A-62F) to be switched to a transmit state while the remainder of the array (60) is in the receive state. This provides for a reference signal during receive calibration, and for single module testing during transmit calibration.