Optical Processor Architectures for Increasing the Range Extent and Range Bins in Range-compressed Radar Images

"The missile defense mission will require wideband radars to perform target imaging, discrimination, and kill assessment of incoming vehicles. Such radars generally produce range-compressed images with fine range resolution (< 1m), a small range extent,and a relatively small number of range bins (1000 to 2000). However, there are applications within the missile defense mission that may require a much wider range extent while retaining fine resolution, and thus a correspondingly larger number of rangebins (e.g., 10,000 to 100,000), to enhance the discrimination of targets in complex RF environments containing strong scatterers, clutter, chaff, decoys, etc. The requirement to generate a large number of range bins from a wideband radar pulse placesextreme demands on the return pulse processor. It would be very difficult and expensive to construct an all-digital processor to perform the real-time, wide-bandwidth, high-resolution spectral analysis of return pulses that is needed to createrange-compressed images. Alternatively, analog optical processing techniques may offer an attractive means to perform this function. The objective of this investigation is to assess the technical feasibility of optical processor architectures that canperform such spectral analysis, and thus can provide a large number, or even a variable number, of range bins. The benefit of this successful technology would allow the use of wideband, arbitrary wavefor