Characterization of the dispersion of a Rotman lens

Abstract

The dispersion of a Rotman lens is quantified by the distortion that a particular Rotman lens would introduce into various pulses. The lens is characterized by broadband measurement of its transfer function. Then this function is numerically applied to the spectrum of a simulated pulse. Aside from a few complications, the resulting function is the Fourier transform of the distorted pulse. It is concluded that, although the Rotman lens is a true time-delay device, practical implementations exhibit dispersion that can be characterized by the method described. The dispersion produces distortion that is probably not significant except in spread-spectrum pulses. For chirped pulses, amplitude distortion may be significant, but it can likely be reduced carefully designing the lens to avoid mismatch reflections.<>