Experimental Validation of an RF‐Over‐Fiber Reference Signal for Frequency Conversion in Large Multi‐Tile Electronically Scanned Antennas

ABSTRACT In this article, a phase‐stable RF‐over‐Fiber (RFoF) link for PLL reference signal distribution and frequency conversion over an X‐band active electronically scanned antenna (AESA) made of multiple subarrays is studied. This RFoF scheme is proposed as an alternative to the traditional coaxial cable approach to provide easier integration in large antennas. The first section of the paper is a thorough description of the considered 1 GHz RFoF link and its main constituents, namely the Laser and Optical Distribution subsystem and the Radiofrequency subsystem. The intended application being emerging AESA gateways for satcom ground stations, the key framework under which its feasibility was assessed is its impact on the radiation pattern of the antenna. To assess the preliminary robustness of the integrated solution to environmental conditions (temperature and vibrations), the performances of a demonstrator have been evaluated and are reported in the second section of the paper. Special attention was paid when investigating the drifting of differential phases between the optical distribution outputs to ensure minimal impact on the antenna beam pointing precision. Featured experimental results meet the requirements for the intended Satcom applications both in the reference and local oscillator frequency bands, thus confirming the industrial capability of the studied solution for large multi‐tile AESA.