Implement and traceability of adjustable EVM on ZigBee signal from vector signal generator

Error Vector Magnitude (EVM) is the most important parameter of modulation quality of wireless digital signal. At present, there are some shortcomings in the calibration process as follows: 1) Lack of vector signal generator that can accurately set the required EVM value of the standard signal, so when calibrating the vector signal analyzer, only the measurement points near the zero modulation error are calibrated. 2) Closed-loop inspection between instruments, using vector signal analyzer and vector signal generator to calibrate the EVM in a closed-loop way. According to the calculation formula of error vector magnitude on digital modulation signal from the vector signal generator, the setting value of I/Q amplitude imbalance and signal-to-noise ratio at a given EVM value of the ZigBee signal are calculated, in the meantime the vector signal analysis software built in the N9030A is used to measure the EVM of the ZigBee signal. The result shows good consistency. At the end of the article, the traceability of adjustments on I/Q amplitude imbalance and signal-to-noise ratio is introduced.