Experimental demonstration of a phased-array antenna optically controlled with phase and time delays

Abstract

The experimental demonstration and the far-field pattern characterization of an optically controlled phased-array antenna are described. It operates between 2.5 and 3.5 GHz and is made of 16 radiating elements. The optical control uses a two-dimensional architecture based on free-space propagation and on polarization switching by N spatial light modulators of p × p pixels. It provides 2(N-1) time-delay values and an analog control of the 0 to 2π phase for each of the p × p signals feeding the antenna (N = 5, p = 4).

Broadband true time delay for microwave signal processing, using slow light based on stimulated Brillouin scattering in optical fibers

“…The tunable TTD induced in our setup allowed a 20% tunability of the FSR of the filter, and the optical carrier phase shifting then enabled to control the origin of the FSR variation, matching the reference frequency. Therefore, we believe that this technique can show the high suitability and key role of slow light for microwave photonics applications Moreover, SCT-SBS true time delay offers simultaneously a continuously tunable time delay and amplitude/phase control while other reported photonic TTD devices provide either continuous delay without amplitude/phase control [5], or discrete delays and phase control [4]. It means that more sophisticated beam forming can be realized with side-lobe reduction and no additional complexity of the system.…”

“…The spacing between adjacent elements d is half of the microwave period. The maximum required true-time delay τ max for a ± 45° scanning is then 15 microwave periods, which is 15/ν RF [4]. Most radars operate between 2 and 20 GHz, which corresponds to maximum required delays, typically ranged from 1 to 10 ns.…”

“…Among the wide diversity of optical delay line schemes that have been reported over the last few years [4][5][6][7][8][9], slow and fast light (SFL) has been devised as one potential approach to generate continuously tunable signal delays. However, the apparent perfect true time delay generated by slow light suffers from two major obstacles: nearly finite delay time-signal bandwidth product and strictly limited operating frequency.…”

Figures of merit for microwave photonic phase shifters based on semiconductor optical amplifiers

“…Some of the most exciting motivations behind the MWP field are attributed to its potential application to implement wideband reconfigurable filters [3], optoelectronic oscillators [2] and optically fed phased array antennas [4]. To this end, the efficient design of broadband tunable microwave phase shifters and true time delay lines is of key importance.…”

Slow Light Effects in Photonic Integrated Circuits with Application to Microwave Photonics

“…To this purpose, the development of RF and data signal processors in the optical domain represents a key point to be accomplished. Among all the functionalities to be developed, the implementation of filtering tasks free from bandwidth constraints [27] and optically fed phase array antenna systems [78] are of great interest. To this end, the efficient design of broadband tunable microwave phase shifters and tunable true time delay lines are critical issues [79,80].…”