TABLE OF CONTENTS Chapter 6, Section 6.4.4, touched on the possibility of mitigating point target multipath null depths to a pair of scanners by attention to heights and operating frequencies. Chapter 7, Section 7.10, showed the resultant RCS of a pair of reflectors to be critically dependent on angle of look and on radar frequency. Figure 12.33(a) depicts one quadrant of the polar diagram of a rudimentary two-point-element target similar to Section 7.10.2, Figure 7.15(f). Initially it might be viewed on bearing ?1, where there is a null in the pattern. Shifting radar bearing a few degrees to ?2 yields a peak. Similarly, shifting frequency a few per cent from f1 to f2 without shift of bearing also moves RCS between a peak and a null. Clearly, viewing at diverse angles or by diverse frequencies partly fills nulls and reduces the probability that a target composed of several reflecting elements will continue to exhibit an extreme of RCS. Also the probability that two uncorrelated observations both yield an extreme value is less than for either radar alone. The probability distribution of RCS becomes more concentrated around the mean, moving part-way to Case 0, making detection possible at lower SNR.
Diversity also decorrelates precipitation clutter and partly decorrelates sea clutter, because the samples differ. Therefore improved detection in noise or clutter is obtained...
