example

 mod = comm.QPSKModulator;

refC = constellation(mod)

constellation(mod)

you will get a figure with constellation of QPSK.

just open file menu>>save as>>

then select "save as type " at the bottom of the new window, you will find pdf in the drop-down window

is this what you want?

Dear Basem M. ElHalawany, thank you so much for your attention but, i'm using " comm.ConstellationDiagram" function, it's a scope block displays there's no save as menu. the solution is gives you a vector graphic in exactly the same size and look, like the last opened scope window with this script :

set(0,'ShowHiddenHandles','On')

set(gcf,'Units','centimeters','PaperUnits','centimeters')

pos = get(gcf,'Position');

set(gcf,'PaperPosition',[0 0 pos(3) pos(4)],'Papersize',[ pos(3),pos(4) ]);

set(gcf,'InvertHardcopy','off','Renderer','painters')

saveas(gcf,'scope.pdf')

Thank you.