A photonic implementation of a wide-band nulling system for phased arrays

Demonstration of a quartic cell, a free-space true-time-delay device based on the white cell

“…Alternatively, the errors can be corrected in the electronic TTDs that would be typically used for the short delays. More recently, fiber Bragg gratings [9], [10] and dispersive fiber [11]- [14] or prisms [15]- [18] have allowed the reuse of the same hardware for different elements, but they require either tunable lasers or multiple lasers with precisely controlled wavelengths. TTDs using free space generally enjoy the advantage of paral- lelism (many light beams share the same free space) [19]- [21], but long delays tend to lead to large volumes because of beam expansion.…”

Photonic Microwave Signal Processing Based on Opto-VLSI Technology

“…In addition, such architectures can only generate discrete true-time delays, making them impractical for broadband null steering (Zmuda et al, 2000). Zmuda et al have reported a few adaptive true-time delay architectures based on the use of multiple tunable lasers in conjunction with high-dispersion fibres for the implementation of broadband nulling in microwave phased arrays (Zmuda et al, 2000;Zmuda et al, 1998). However, the use of multiple tunable lasers requiring continuous calibration makes the system implementation very expensive and impractical.…”

“…Fig. 10(a) shows a typical N-element phased-array antenna architecture, whose array factor (or directional response) is given by (Zmuda et al, 1998):…”

Hardware Demonstration of Extremely Compact Optical True Time Delay Device for Wideband Electronically Steered Antennas

“…Fiber-or waveguide-based approaches switch beams among waveguide paths of varying lengths [2]- [6] or use multiple wavelengths and dispersion to create relative delays [7]- [10]. Fiber lengths can be arbitrarily long and have low loss but the lengths are difficult to control accurately.…”