.PS
cct_init

# Usual defs...
qrt=dimen_/4;
hlf=dimen_/2;
dim=dimen_;

Org:Here
line -> from Org-(2*dim,0) to Org+(2*dim,0); " I"  ljust_
line -> from Org-(0,2*dim) to Org+(0,2*dim); "Q " rjust_
setrgb(0,0.75,0)
O1:dot(at (dim,dim)); "00" at rvec_(0,3mm__)
O2:dot(at (-dim,-dim)); "11" at rvec_(0,3mm__)
O3:dot(at (dim,-dim)); "01" at rvec_(0,3mm__)
O4:dot(at (-dim,dim)); "10" at rvec_(0,3mm__)
resetrgb
setrgb(0,1,0)
line from O1 to O2
line from O3 to O4
resetrgb
# Wanted this in green too: Perfect, exept arrowhead are black....
arcdimension_(from (0,dim) to (0.707*dim,0.707*dim) \
  cw with .c at Org,,$\frac{\pi}{4}$,3mm__)

# Offset QPSK by 45 degrees
dot(at (0*dim,1.4*dim)); "00" at rvec_(0,3mm__)
dot(at (0*dim,-1.4*dim)); "11" at rvec_(0,3mm__)
dot(at (1.40*dim,0*dim)); "01" at rvec_(0,3mm__)
dot(at (-1.4*dim,0*dim)); "10" at rvec_(0,3mm__)

"\tiny DQPSK" at (dim,-1.5*dim)
.PE