True-Time-Delay Beamforming With a Rotman-Lens for Ultrawideband Antenna Systems

An analytical design model for Rotman-lenses is presented, with an accurate treatment of the return loss of the ports and their phase centers. The detailed design equations allow a very fast prototyping prior to numerical simulations for the final adjustment. Based on the presented model a prototype has been built for the true-time-delay phasing of an antenna array for the ultrawideband frequency range from 3.1 GHz - 10.6 GHz. Measurement results of the prototype together with an antenna array for transient systems are presented in the time and frequency domain.