RF photonics for simultaneous beam imaging RADAR

Abstract

There is a growing need for RADAR systems to address short range sensing problems where standard electro-optic sensors are impeded. From convoy situational awareness to rotorcraft brownout, there are a growing number of military requirements to address degraded visual environments (DVE) where new solutions are needed to provide feedback to the operator in both manned and unmanned platforms. In such environments, millimeter-wave RADAR could potentially provide the necessary obscurant penetration for sensing in DVE, while maintaining sufficient resolution for operational awareness. However, to achieve real-time, low-latency sensing as required for most military applications, traditional raster swept beam approaches to spatial image formation cannot provide sufficient update rates for modest sensor field of regard and image resolution. Additionally, for such short range applications RADAR instantaneous bandwidths must be high to accommodate range resolutions commensurate with the application. One approach that is being taken to create more flexible RADARs for these and other applications, is to use active electronically scanned array (AESA) technologies combined with digital beamforming, where multiple beams can be analyzed simultaneously using digital processing techniques. However, such techniques require immense processing bandwidths as each beam to be formed in a given time window must be processed at a rate sufficient to encompass the instantaneous bandwidth of the RADAR return. As such, limits on processing power often limit the beam-bandwidth product that can be achieved using digitally beam formed arrays.