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I understand using the pattern to find the output line single phase but how is the amplitude determined?

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But how is the amplitude determined?

By the length of the line from the origin to each constellation point: -

enter image description here

The above image has equal amplitudes for all four binary values hence they sit on the circumference of a circle.

The one below has 8 binary values and the amplitude of the inner four is smaller than the outer four.

enter image description here

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  • \$\begingroup\$ Is this true as well for a binary signal? \$\endgroup\$ Commented Jan 23, 2020 at 16:48
  • \$\begingroup\$ It usually is but needn’t be theoretically. BPSK (binary phase shift keying) is a good example of two points having equal amplitude but a phase angle of 180 degrees between the two signals. \$\endgroup\$
    – Andy aka
    Commented Jan 23, 2020 at 16:50
  • \$\begingroup\$ So first image is 1v. 5v, 0v range second image would be 1v, 0.75v ,0.5v 0v range? \$\endgroup\$ Commented Jan 23, 2020 at 16:59
  • \$\begingroup\$ I don’t know how you arrived at those numbers frankly. In the 1st diagram, all amplitudes are the same because all four binary vales are represented on one circle having a constant radius. \$\endgroup\$
    – Andy aka
    Commented Jan 23, 2020 at 17:04
  • \$\begingroup\$ If you are wondering how each constellation point is ascribed a binary value then that is completely arbitrary. The example binary values in my pictures are purely examples and need not be like that. \$\endgroup\$
    – Andy aka
    Commented Jan 23, 2020 at 17:06

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