ALLPCB
Overview
EVM (Error Vector Magnitude) is a commonly used measure of signal quality in wireless communication systems. It evaluates the performance and accuracy of a modulated signal to determine the integrity and efficiency of signal transmission. EVM is an important metric when designing and optimizing wireless systems, as it helps assess system reliability and efficiency.
Basic concept of EVM
EVM is defined as the difference in amplitude and phase between an ideal reference signal and the received signal, represented as an error vector. It is commonly expressed as a percentage or in decibels (dB). Lower EVM values indicate better signal quality, meaning less distortion and improved system performance.
EVM calculation
First determine the ideal reference symbol positions, then measure the deviation of the actually received symbols from those ideal positions. These deviations are the error vectors. EVM is the root mean square (RMS) of the magnitudes of these error vectors normalized to the RMS amplitude of the reference signal.
Factors affecting EVM
- Local oscillator (LO) phase noise: nonlinear circuit elements introduce phase noise.
- DC offset in baseband I/Q signals and poor LO isolation can cause carrier leakage or LO leakage.
- I/Q imbalance.
- Nonlinearity in transmit or receive paths.
