Phased Array Radar Initial Alignment Algorithm Using Mutual Coupling: An Iterative Approach

Using a mutual coupling based calibration technique, a platform agnostic algorithm is developed to perform an initial alignment on phased array radar systems without the use of external equipment (far-field sources, near-field chambers and probes) or the need to implement additional internal calibration networks to already existing systems. By using coupling pairs from mutual coupling measurements, an overdetermined system of equations is created and solved. The solutions of the overdetermined system are the least-square error estimated complex gains of each element channel. A pre-phasing routine is implemented on the element channels to avoid possible phase ambiguity issues in the results since fully digital radar systems may contain phases from all possible angles (-pi:pi). Another improvement implemented to the algorithm is an iterative solution that can reduce the errors of the estimated results and also further aids in avoiding phased wrapped results. For diagnostic purposes, the algorithm can determine if an element has failed in either receive or transmit mode and then perform the initial alignment while ignoring the failing elements to avoid introducing errors from these failed elements. The algorithm is compatible with dual polarized systems.