Radar Array Processing
Special Thanks to Lingchen Zhu
A radar array, or we call it, phased array antenna, is composed of lots of radiating elements each with a phase shifter. Beams are formed by shifting the phase of the signal emitted from each radiating element, to provide constructive/destructive interference so as to steer the beams in the desired direction.
Why are phased array antennas of interest? Not only because it is now widely used for broadcasting, naval usage (e.g. warship communication), space probe communication, weather research, radio-frequency identification (RFID), human-machine interfaces (HMI) and optics, but also its main advantage is the nearly infinitely fast switching of the look direction of the array. This allows to illuminate the search space according to some optimality criterion instead of according to a continuous mechanical movement. All aspects of optimizing target illumination the received energy are denoted by the key word energy management, which is the principle advantage of phased arrays. Particular components of energy management are:
- Coherent integration can be made nearly arbitrarily long. This allows better clutter suppression (Doppler discrimination), target classification by extracting spectral features, and finally Synthetic-aperture radar (SAR) and Inverse synthetic aperture radar (ISAR) processing.
- Performance of different radar task in time multiplex, like search and tracking of multiple targets. This allows to use one phased array radar as multi-function radar.
- Optimisation of individual radar tasks: optimised waveforms for search, acquisition and track, high precision measurements when required, variable beam shapes, optimised algorithms for tracking (the radar is “steered” by the tracking algorithm and a-priori information).
- Lower prime energy consumption
- High mean time between failure (MTBF) due to graceful degradation
- If spatial samples over the antenna aperture are available: adaptive beam forming (ABF), space-time adaptive processing (STAP), super-resolution.
Some other important techniques of phased array antenna include but not limited to: beamforming, radar detection, parameter estimation, etc.