Meaning
A reduction in the modulation accuracy of a transmitted radio frequency signal, measured as an increase in error vector magnitude. An EVM degradation occurs when physical or electrical impairments distort the constellation points of a modulated signal.
Signal Impairment
Non-linear behavior in the power amplifier or phase noise in the local oscillator drives this signal distortion. High operating temperatures within a sealed enclosure often worsen the effect. The EVM degradation translates directly into higher packet error rates and reduced communication range.
Hardware Boundary
System designers must budget for the impact of board-level shielding and antenna mismatch on the transmitter. While an isolated chip might output a clean signal, the EVM degradation observed in the fully assembled product is frequently higher due to return loss. This difference defines the boundary between chip-level performance and system-level performance.
Calibration Test
Production engineers execute automated test scripts during final assembly testing to measure the modulation quality under maximum load conditions. If the measured transmitter performance falls below the limit defined in the wireless standard, the test software rejects the assembly. This testing ensures that every shipped device maintains the required link margin in the field, even when operating at maximum transmit power or under high thermal stress.
