Well-posed well-conditioned phase retrieval technique using a known reference source

We propose simple method for retrieving the phase of the electromagnetic field radiated by an arbitrary source fed by a current I/sub s/ from plain intensity measurements. The method consists in adding a known reference radiator suitably placed, and fed by a current I/sub r/, and measuring the field intensity at each point in four different situations: (i) I/sub s/=I, I/sub r/=0; (ii) I/sub s/=0, I/sub r/=I/sub 0/; (iii) I/sub s/=I, I/sub r/=I/sub 0/; (iv) I/sub s/=I, I/sub r/=I/sub 0/e/sup jx/2/. The resulting phase-recovery problem is well-posed and well-conditioned. We show that the resulting phase accuracy can be made better as compared to standard techniques.