What is the recommended capture length to get reliable WLAN Error Vector Magnitude (EVM) results in a production environment?
Capturing and analyzing an entire packet is generally not necessary to get accurate and stable EVM measurement. In a production environment that can take an excessive amount of time.
As a starting point, the capture length can be derived as follows:
- For OFDM packets: The minimum capture length = pre trigger time (10 us) + OFDM preamble length (20us)+ OFDM symbol length (4us)* number of OFDM symbols (at least 16)
- For DSSS/CCK: The minimum capture length = pre trigger time (10us) + preamble length (192us for long preamble and 96us for short preamble) + number of chips (at least 1000)/data rate