The most demanding requirements for radar systems have so far nearly always resulted from military objectives; civil applications then benefit from the achieved results. Developments in the available technology, particularly within the areas of highly integrated semiconductor technology for digital signal processors, miniaturised microwave integrated circuits (MMIC) and efficient microwave computer-aided design methods, have enabled ever more demanding procedures and concepts to be achieved. The theoretical fundamentals and evaluation possibilities have improved simultaneously, especially with the development of computers and software. The use of powerful personal computers with program systems such as MATLAB or Mathematica is now very common.

Processing of the received signals is performed after an analogue-to-digital conversion in suitable digital signal processors or computers. Performance improvement is characterised by the measurement of the received signals with increasing precision and sampling rate. The necessary signal-processing operations are achieved with ever higher data rates and computing power. So it is possible to achieve real-time operation for more and more sophisticated signal and data-processing algorithms. From the received target signals the target location, parameters, features and even images for classification are then derived.

The extended requirements of today's and future radar systems are the following:

• Detection of targets with small radar cross section (stealth targets) and at long ranges with high detection probability and low false-alarm probability.

• Detection of targets under extreme conditions:

  • objects flying at very high or low altitude

  • Objects emerging with high or very low speed

  • targets flying or moving in shadow

  • targets emerging for a short...