Introduction
Error vector magnitude (EVM)
measurements can provide a great
deal of insight into the perfor-
mance of digital communications
transmitters and receivers. With
proper use, EVM and related mea-
surements can pinpoint exactly
the type of degradations present
in a signal and can even help
identify their sources.

Primarily a measure of signal
quality, EVM provides both a sim-
ple, quantitative figure-of-merit
for a digitally modulated signal,
and a far-reaching methodology
for uncovering and attacking
the underlying causes of signal
impairments and distortion. EVM
measurements are growing rapid-
ly in acceptance, being already
the required modulation quality
measurement in such important
technology standards as 3GPP
W-CDMA and IEEE 802.11a/b/g
WLAN, and they are poised to
appear in several upcoming
standards.
This application note provides
useful tips that will assist in accu-
rately making and understanding
EVM measurements.