The QPSK EVM measurement is to determine the error between the transmitted signal of a UE and the desired ideal signal. The measurement is very similar to the Waveform Quality measurement. The difference is that the expected input signal is a QPSK modulated signal, which is similar to the WCDMA uplink signal with only one code channel. The data carried by the QPSK symbols sequence can be any pattern.
This measurement is designed for the UE to calibrate its IQ modulator without a WCDMA format signal to meet the waveform quality requirements as defined in 3GPP TS 34.121.
Please note that the measurement results will only be valid if a pure QPSK modulated input signal is applied.
Triggering choices are immediate, protocol, external, auto, and HS-DPCCH ( lab application or feature-licensed test application only ). See Trigger Source Description for more information.
Auto triggering is the default choice. In most cases, auto triggering provides the optimum measurement triggering condition for the waveform quality measurement. For example, if the UE is synchronized to the test set, auto triggering causes protocol triggering to be used. Auto triggering causes immediate triggering is used if the UE is not synchronized. When immediate triggering is used, the measurement result returned for timing error is always
NAN
(Not a Number) because it is not possible to evaluate a timing error in this measurement situation.
You can move the measurement interval (666.7 us = 1 timeslot) relative to the trigger using the
Trigger Delay
setting.
Selects whether or not to include the original offset from the evaluated signal before calculating the EVM.
This measurement should be calibrated using the Calibrate Measurements function ( CALibration:MEASurements? ) when the temperature has changed by ± 10° C or more since the last calibration. If this situation exists, the integrity indicator value becomes 19 and a message is displayed indicating "Uncalibrated Due to Temperature".