  A linear and thus convex phase retrieval algorithm for the application in
phaseless near-field far-field transformations is presented. The formulation
exploits locally known phase relations among sets of measurement samples, which
can in practice be acquired with multi-channel receivers. Due to the linearity
of the formulation, a reliable phaseless transformation is achieved, which
completely avoids the problem of local minima - the Achilles heel of most
existing phase retrieval techniques. Furthermore, the necessary number of
measurements are kept close to that of fully-coherent antenna measurements.
Comparisons with an already existing approach exploiting local phase relations
demonstrate the accuracy and reliability for synthetic data.
