Generally, a series of echo signals is the basis for target detection. An arbitrary length of this series is applicable by using the beam agility, which enables adaptation of the transmit energy to target strength and of the required Doppler resolution. The step-scan operation of a phased array provides an important difference when compared with mechanical scanning radars with respect to the detection procedure and clutter suppression. Clutter suppression may be divided between strong fixed clutter and varying Doppler-shifted clutter, the first of which may be suppressed by a simple recursive filter. Using post processing the latter can be arranged advantageously, in an adaptive manner, after the filter-bank. Sea clutter suppression can be improved by a special multiplex operation of the beam, resulting in elongated dwell times in each BP. For a longer series of pulses, a possible Doppler shift during the dwell time has to be considered. The usual filter bank shows a degraded detection performance because the target energy is distributed into several filters. An autocorrelation estimation test will give a more robust performance in this case. The detection performance is evaluated and compared on the basis of simulation studies.

Chapter Contents:

• 8.1 Filter against fixed clutter
• 8.2 Doppler filter processor
• 8.3 Adaptive suppression of weather clutter
• 8.3.1 Computation of the gain
• 8.3.2 Evaluation of experimental signals
• 8.4 Suppression of sea clutter
• 8.5 Estimation of Doppler frequency
• 8.5.1 Accuracy of Doppler estimation by Cramér-Rao bound
• 8.5.2 Simplified Doppler estimator
• 8.6 Coherent detection with long pulse series
• 8.6.1 Variable Doppler frequency of the target signal
• 8.6.2 Coherent test function for long echo series
• 8.6.3 Comparison of detection performance of the filter bank and ACE-test for LFM Doppler signals
• 8.7 Conclusions
• References

Inspec keywords: correlation methods; Doppler radar; phased array radar; recursive filters; object detection

Other keywords: step-scan operation; autocorrelation estimation test; target detection; recursive filter; phased array; sea clutter suppression; Doppler-shifted clutter; echo signal; beam agility; Doppler resolution; pulse series

Subjects: Radar equipment, systems and applications; Filtering methods in signal processing