TABLE OF CONTENTS This chapter contains some notes and issues concerning the implementation of adaptive space-time or space-frequency filters for clutter suppression in airborne MTI radar. A comparison of the computational load of all techniques discussed in this book is given in Tables 15.1-15.4. The key findings and issues can be summarised as follows
Tolerances of sensor positions degrade the performance of those processors which are based on equispaced arrays. This concerns mainly those processor architectures using spatial transform techniques with linear or rectangular planar arrays (see Chapter 6). The optimum processor and the auxiliary space-time channel processors are not sensitive to errors of the sensor positions. In conclusion we can state that the dramatic reduction of computational expense offered by the spatial transform has to be paid for in terms of high accuracy of the antenna channels.
Antenna channel errors of various kinds in connection with the radar system bandwidth have been analysed by Nickel [374]. IQ errors cause an increase of interference eigenvalues while delay errors may compensate for them to a certain extent The increase in the number of eigenvalues has to be countered by additional degrees of freedom of the processor.
There are channel equalisation techniques to compensate for all kinds of differences between channels. Ender's technique adjusts both the frequency responses in the range and the echo time dimensions in the frequency domain. This technique requires long echo data sequences as is common in SAR syatems. Channel error compensation for short data sequences...
