Photonic correlation for wideband processing in MMW imaging systems

摘要

In recent years, many examples have been cited where photonic signal processors have the potential of enabling the deployment of wideband RF sensor systems whose data rates would otherwise overwhelm the capabilities of traditional digital signal processors. Passive, synthetic aperture millimeter-wave (MMW) imaging arrays are one such class of sensor system that offers a solution to the need for a passive, all-weather look-down sensor for critical DoD and environental missions. A photonic method of correlating the signals received by the various elements of the array offers a highly efficient, exceptionally wideband capability, exploiting a powerful new technology for aperture-shnthesis imaging. Our trade study has helped to establish that a photonically based interferometric imager can significantly reduce the weight and power consumption of the system relative to an all-digital-electronics approach. In addition, the ability of an airborne or space based system to process multi-gigahertz bandwidths offers the first real-time MMW imager operating at video rates. Previous demonstrations of optical correlators have used discrete components, and generate only the real part of the correlation. Using integrated optical waveguide technology developed in part for the telecommunications industry, we have developed an approach for computing complex correlations over wide bandwidths and in such a way to allow video rate imaging for passive MMW systems.