In case 3, to realize much lower PSLL with acceptable PSBL, the ring spacing, the number of elements, and the normalized switch-on time sequence for each ring are all optimized.
Individual A has the lowest PSBL, and individual B has the lowest PSLL.
From the picture, it can be seen that the PSLL varies inversely proportional to the PSBL.
Obviously, individual [A.sup.1] has the lowest PSBL, but its PSLL is also the highest.
The PSLL varies from -24.34 dB to -42.70 dB, and the PSBL varies from -12.06 dB to -40.28 dB.
From the figure, it can be seen that the Pareto front offers a set of solutions which have the tradeoff between the PSLL and the PSBL. We may find different design parameters for different requirements from the Pareto front.
Individual [A.sup.3] has the lowest PSBL with highest PSLL.
In this design, the PSLL and the PSBL are set as two objectives.