Calibration standards for digital modulation error based on CW, AM or PM signal

Digital modulation signal is the main bearer of modern information transmission; modulation error parameters include Error Vector Magnitude (EVM), MagErr and PhaseErr. However, there are problems for metrology of digital modulation error: first, the signal source and vector signal analyzers calibrates each other, and forms a closed-loop, the calibration is not traceable. Second, digital modulation error are set in the “0” point in calibration. To solve the problems, we propose a new method: use combination of two CW, analog AM or PM signal, to construct an “equivalent MPSK signals” with certain modulation error. The equivalent MPSK signals´ EvmRms, EvmPeak, MagErrRms, MagErrPeak, PhaseErrRms and PhaseErrPeak is are solely decided by power ratio of two CW, or by AM depth or PM phase deviation, and can be calculated accurately, and are continuously adjustable within a wide range. Experiment shows that the method is effective. This has established a standard signal with digital modulation error, it´s could be used to calibrate vector demodulation functions of vector signal analyzer (VSA) and wireless communications tester.