Introduction to real aperture array radar

The evolution of radar proceeded in a number of steps, of which each had a fundamental effect on the performance. In the beginning, the radar was built using all analogue technology with an analogue display. Information extraction was performed at that time by adjusting the dynamic range of the cathode-ray display. A big improvement was obtained when the output data after analogue filtering and signal processing were sampled and digitized. This allowed some post processing of these data. A number of detection techniques with different algorithms and adaptive thresholds could be implemented. The algorithms could be changed by software if necessary. Digital displays provided a clear extraction of the relevant information. With the increasing availability of fast analogue-to-digital converters and computers, the point of digitization could then be shifted more and more towards the antenna such that programmable filters and signal processing algorithms could be applied. This allowed to apply all the flexibility of digital signal processing in the time domain.