True time delay beamforming using fiber optic delay lines

Elimination of phased-array beam squint is demonstrated at S-band by means of a single mode fiber optic beamforming network employing time delays. Phase linearity of the beamformer is examined as a function of frequency using electrical S-parameters measured at the external ports of the network. Microwave reciprocity and true time delay behavior of the passive fiber optic components within the network are examined using S-parameters measured with an optical test set. Overall beamformer performance is characterized by ideal linear phase variation with frequency and by nonsquinted radiation patterns measured over a 50% instantaneous bandwidth from 2.0 to 3.0 GHz. It is concluded that these results clearly show that single-mode microwave fiber-optic networks can be used to achieve true time delays for array antenna beamforming and for microwave applications in general.<>