Improved stability against electrical dc bias drift has been demonstrated in LiNbO3 electro-optic modulators by replacing the commonly used SiO2 buffer layer with indium tin oxide (ITO), a transparent conductor. The long term drift of the modulators having an ITO buffer layer with a sheet resistivity of ∼20 Ω/⧠ is less than 0.3% in 8 h. The mechanism of the dc drift phenomenon is discussed using an electrical equivalent circuit model of the modulator.
the fiber, increased noise level because of fiber dispersion, and perturbations over the long fiber length. When reflections are low, the link is stable and the SNR for the fiber optic links meets the -130 dBc/Hz needed for most radar test set applications.
CONCLUSIONSWe have demonstrated that fiber optics can improve the capability of radar test set systems. They provide delays longer than practical with coaxial cables or waveguides. This will allow performance measurements to be made on modem Doppler radars. The results show that fiber optic links will meet the signal-to-noise requirements of modem radars and potentially will have many radar and electronic warfare applications in the near future.
ACKNOWLEDGEMENTThe authors acknowledge support of and useful discussions with M. Radant, L. Seeberger, and G. Wagner of Hughes Radar System Group (RSG) and A. Popa of Hughes Research Laboratories. We also acknowledge Ortel Corporation for providing a prototype fiber optic link.
ABSTRACTThe use o j opticul fibers us the deluy line element in rudio frequency memorv loops. promises light weight and smull size devices with long time delu,vs. This paper presenis the experimental results und performunce analysis of u 2-6-GHzfiber optic recirculating deluy line.
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