Phase-error performance of multi-focal and non-focal two-dimensional Rotman lens designs

The phase errors of the conventional trifocal Rotman lens and its modified quadrufocal designs could be reduced by adopting a non-focal design scheme. The non-focal design produces minimum average phase errors for all beam ports rather than achieving zero-phase error for only selected focal points. Fundamental models of designing and optimising typical trifocal and quadrufocal planar bootlace lenses are reviewed. Results based on the non-focal design method are compared to the ones from conventional designs, and noticeable improvements demonstrate that the non-focal design scheme is an alternative way of optimising the phase errors for the Rotman lens design. As in referenced papers on multiple-focal designs, the emphasis is on the phase-error analysis and not on experimental verifications.