Analysis of a radar beamformer based on a photonic delay line

Abstract

A photonic means of generating the element-to-element phase shifts required for the operation of a true time delay radar beamformer was developed previously by Toughlian and Zmuda for systems operating in the VHF frequency range, and extended by Monsay for operation in the radar C band. The photonic beamformer is based on an acousto-optic (AO), heterodyne optical system in which the reference beam acts as a probe of the acoustic wave in the AO cell. The time delay of the acoustic waveform readout by the optical probe from various locations along the length of the AO cell can then be imposed directly on the microwave elements of the radar beamformer, providing the correct phase for each element at whatever frequency drives the AO cell. Fundamental systems-oriented calculations are reported. Results for both optical specifications and radar performance specifications are obtained based on a mathematical model of the photonic delay line previously developed by the author. These results address the use of the photonic delay line in a standard radar beamformer. © 1997 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(97)01412-8]