We proposed an optical true time-delay (TTD) feeder for X-band linear phased array antennas (PAAs), which possesses high-speed beam scan capability by selecting different lengths of fiber delay lines with fast 2 2 optical microelectromechanical system switches. For proof of concept, a 3-bit optical TTD has been built for a 10-GHz linear PAA composed of two antenna elements. Experimental results show that the maximum time-delay error is less than 0.2 ps, corresponding to a radiation angle error of less than 0.84 , which is within the equipment resolution. We have also designed a 10-GHz linear PAA composed of eight microstrip patch antenna elements driven by the proposed TTD. The radiation patterns of this PAA have been obtained by simulation.Index Terms-Beam forming networks, optical microelectromechanical system (MEMS), phased array antennas (PAAs), true time-delay (TTD).
Multisection semiconductor lasers for optical microwave generation have been fabricated that consist of a loss-coupled distributed feedback (LC-DFB), a phase control, and an amplifier section. High-frequency self-pulsations are generated according to the concept of a single-mode laser with short optical feedback. The effect of the optical feedback via the phase control and the amplifier section on the self-pulsation is apparently shown as a result of the superior single-mode characteristic of the LC-DFB section. Continuous frequency tuning is achieved in the range of 17-35 GHz.
We show that both cross and bar states with high extinction ratios larger than 30 dB can be achieved at the same end of ultra short fused vertical directional coupler switches (FVCSs) with two sections by changing the refractive indices of cores and inner cladding layer less than 1%. The improvement of extinction ratios for various combinations of the refractive indices in a two-section FVCS is studied using the improved coupled theory and beam propagation method. Design guidelines to achieve high extinction ratios with large tolerances are presented.
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