virhevektorimagnitude

Virhevektorimagnitude, often translated as error vector magnitude (EVM), is a common metric used to quantify the performance of a digital radio transmitter or receiver. It measures the difference between the ideal signal constellation and the actual transmitted or received signal constellation. In simpler terms, it indicates how "far off" a real signal is from its intended perfect representation.

The concept of EVM is rooted in the signal constellation diagram, which plots the amplitude and phase of a digital signal at discrete time intervals. For a given modulation scheme, such as Quadrature Amplitude Modulation (QAM) or Phase-Shift Keying (PSK), there is a set of ideal points or "constellation points" that represent the perfect data symbols. Real-world transmission and reception are subject to noise, interference, and non-linearities, which cause the actual signal points to deviate from these ideal positions.

EVM is typically expressed as a percentage, where a lower percentage indicates better performance. It is calculated by finding the Euclidean distance between each actual signal point and its nearest ideal constellation point, summing these distances, and then normalizing the result by the magnitude of the ideal signal. This provides a single, comprehensive measure of signal quality. High EVM can lead to increased bit error rates and reduced data throughput.