True-time-delay beam forming using Bragg grating resonators

A new photonics concept for true time delay beamforming and steering is described. To delay a signal an array of fibers, or other optical waveguides, containing cavities of different resonant frequencies are used to channelize the signal. Each spectral component of the signal is phase shifted by an amount proportional to the frequency of that spectral component and proportional to the time delay desired. These phase shifted spectral components are then summed to obtain the delayed signal. This new approach does not rely on switching between different lengths of delay lines. As a result, the pointing direction of an antenna array can be finely controlled over a continuum of angles, and the time to change direction can be on the order of 10 nanoseconds or faster. The concept has been refined, analyzed, and implementation issues addressed. The approach appears to be feasible. All the integral components with characteristics necessary to meet the requirements of an operational true time delay beamforming system are realizable. The time delay module as a channelizer has a number of alternate applications. For electronic warfare the channelizer provides the ability to analyze a wide bandwidth signal on the order of tens of Gigahertz at a resolution of 10 to 20 Megahertz. As a wavelength demultiplexer in optical communications, it would allow for a greatly increased density of channels within a given spectral range.