Chapter 3Space-time Exploration for Airborne Radars1




3.1. Introduction

Long range airborne surveillance is a very demanding application for radar designers, and now generally requires active antennas (multiple transmitters), improved power budget, increased availability and beam agility and adaptivity. Fixed targets are detected with high resolution SAR, requiring instantaneous bandwidths ranging from 500 MHz to 1 GHz, and moving air and ground targets are detected with MTI modes using space-time adaptive processing (STAP) for clutter rejection – which requires multiple channels on receive. This means that modern airborne radars generally implement multiple channels and wideband transmit/receive radio-frequency front-ends.

Taking that specificity into account, we must determine the best waveform and scanning strategy for a specific surveillance mission, taking into account the very limited time available for surveillance of wide areas at long range.

The purpose of this chapter is to outline the main possibilities and to show that the simultaneous requirement for wideband and multiple channels opens the way to new beamforming techniques and waveforms, where different colored signals are simultaneously transmitted for coding space and time, and coherently processed in parallel on receive. Such concepts, first proposed and demonstrated by S. Drabowitch [DRA 68] and J. Dorey [DOR 78], should now be considered as mature techniques to be implemented on operational systems.

This ...

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