Simultaneous air/air and air/ground radar modes with a single antenna

Abstract

We describe an original way to realize air/air and air/ground radar detection modes simultaneously with a single sub-arrayed antenna of an airborne radar system. Co-located MIMO techniques a.k.a. colored transmission are natural candidates to address this problem, however in an airborne context the angular coverage enlargement they provide is not enough to explore the nominal search domain associated to the functions to be implemented. The solution described in this work consists in subdividing the antenna into two transmitting sub-arrays; Unlike classical MIMO techniques, the pulse repetition interval and the pulse durations are not constrained to be the same in all the transmitted waveforms, which allows the re-use of already developed, qualified, and operation-proven waveforms (@Thales patented). On the receiving side, assuming a sufficient number of Rx sub-arrays, ground clutter echoes can be mitigated with STAP. Since signal reception in a sub-array is not possible during transmission through another one, missing data in receiving channels yield specific signal processing issues. New results are provided with the example of the AMSAR antenna architecture, and comparisons are made with other methods based on interpolation with autoregressive models when missing data are due to e.g. intermittent jamming or interactions.