EVM is one of the key TX design spec. EVM is a measure of signal quality. It is a measure of in-band distortion and noise while ACLR was a measure of out-of-band distortion and noise. Funny enough that since it is in-band, you do not care as much about it as ACLR. If distortion is leaking in neighboring band, you have to fix it right away. If distortion is falling in-band, you are like:
“ahh okay, will see how much do I need to fix it, maybe I can still play some trade-offs in my system to do something about (and by the way I didn’t impose very demanding distortion specs on myself, things fall in-band, I take care, these ACLR folks are outrageous, they just don’t want you to emit anything outside), enough blabber, I will fix it, don’t worry, let me see what’s wrong with ACLR first”
Okay, but how would you fix EVM? We need need to decompose EVM into different metrics to understand what factors contribute to it, and thereby optimize/debug it with proper insights.
TX EVM is composed of three main components: distortion, noise and leakages as shown below.
Published: 14 Jan 2023
Last Edit: 14 Jan 2023