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A four-phase and an eight-phase signal constellation are shown in the figure below.

For the constraint that the minimum distance between pairs of signal points be $d$ for both constellations, the radii $r_1$ and $r_2$ of the circles are

1. $r_1=0.707 d, \; r_2=2.782 d$
2. $r_1=0.707 d, \; r_2=1.932 d$
3. $r_1=0.707 d, \; r_2=1.545 d$
4. $r_1=0.707 d, \; r_2=1.307 d$