# Phase versus time graph of QPSK

In wikipedia, there was an example on QPSK modulation where the main signal was 11000110 and I contained 1001 and Q contained 1010, now their output was shown by the Signal in the figure.

Now according to constellation diagram Signal can be represented as

11 -> pi/4
00 -> -(3*pi)/4
01 -> (3*pi)/4
10 -> -pi/4


But my confusion was in the phase vs time diagram shown in another figure given below

For 11 it starts from phase pi/4, but for 00 shouldn't the phase start from -(3*pi)/4 = -135 ?

• Um, I'm not sure I understand what you're asking here. Are these diagrams linked? The mapping of bit groups to constellation points is arbitrary (in reality, gray coding puts a restriction to arbitrarity). – Marcus Müller Aug 31 '18 at 6:56