EVM and spectrum mask question

Hello, everybody
I think this is a simple question for RF expert. What is the EVM, and how to measure the EVM ? and the relationship between spectrum mask?

EVM:

h**p://rfdesign.com/mag/411rfdf4.pdf

y can use the AGILENT E4445A to meaure the EVM;
this is a cheap way;

or y can use the vector signal analyzer to measure the EVM

dear
you can visit the @ilent website for more info about EVM test. I saw the EVM test for GSM/EDGE PA output signals. all done by @gilent E4406 VSA instrument.

There really isn't a relationship betweem EVM and spectral mask. For example, you could have a sign error in you baseband I/Q setup, so that your bits are inverted. You'd see the same spectral mask, but your evm would be bad.

Have a llok to the Agilent note

Agilent, Using EVM Measurements to Analyze and Troubleshoot Vector-Modulated Signals (PN 89400-14)

can be downloaded from:
www.agilent.com