phase noise evm

EVM (%) = 1.74 * RMS Phase_error (°)

HI Vfone

Could you please explain the formula if possible?
Some Stuff related to this fomula?
Thanks in advance.

Sorry for a dummy question, but what does EVM stands for?

Hi,


Error Vector Magnitude (EVM)
The best EVM (approximately 1.0%) is achieved when all imbalances are set to zero.

Very useful document on "Interpret And Apply EVM To RF SystemDesign" is attached...

additional info. on EVM

Error Vector Magnitude (EVM) is a figure of merit for modulation accuracy. Any device that exhibits AM-AM and AM-PM distortion such as power amplifier will degrade the EVM.
The DSP stages such as pulse-shaping filters and D/A conversion can have a significant effect on overall EVM

i.e the impact of phase imbalance, amplitude imbalance, and dc-offset you can see on the EVM measurement...The best EVM (approximately 1.0%) is achieved when all imbalances are set to zero...

Also
The EVM measurement is described mathematically as:

|(Vrx - Vref)|^2
EVM (%) = 100 * -----------------
|Vref|^2

where Vrx is the complex received signal (from the demodulator) and Vref is a perfect (ie undistorted) complex reference signal.

Not only the EVM-rms is important but also the spectral distribution. That is common known as phase noise. If the lower frequency components are higher some phase/frequency synchronisation methods give different perfromance results than by using flat frequency noise.

Agilent application Note is useful

Agilent PN 89400-14A

http://cp.literature.agilent.com/lit...5966-0444E.pdf

Quite good document for me.
And it helps for me doing EGPRS RF system debugging.
Thanks!

How to measure the AM-AM and AM-PM distortion of power amplifier ?what kind of setup required

I think you need a Vector signal analyzer

My opinion is that is useless to compute EVM in other way than measuring it.

EVM = 2 * sin(phase error[degree] / 2) *100%
ex: a 0.35degree ems phase error will cause 0.61% EVM