Preliminary Technical
Data
Rev. PrA | Page 35 of 82
Figure 37. Direct EVM for the Best ACLR Performance
Observation Receiver Attenuation vs Stability Metrics
Shown below is the trend for the EVM and error stability metrics for different observation receiver channel attenuation values. It
can be observed that as observation receiver attenuation is increased, the error percentage also increases. The same might be
true for a low SNR transmitter to observation receiver channel. It is advised to increase the threshold for stability metrics as the
observation receiver attenuation increases or the channel SNR decreases.
Figure 38. ORx Attenuation vs. Stability Metrics
Observation Receiver Interference
Although unlikely, any interference in the observation receiver channel can cause DPD instability and can cause the firmware to
derive wrong DPD coefficients resulting in poor performance as shown below in Figure 39, which includes the bench
characterization of observation receiver interference levels affecting ACLR and stability metrics. Depending on the application
and the ACLR performance, the user can budget for the threshold of stability metrics. T1 represents the ACLR degradation at 5%
indirect EVM, and T2 represents ACLR degradation at 15% EVM. Data2 represents the absolute value of ACLR in dBm as the
power level of the interferer injected into the observation receiver increases. The total carrier power of the primary signal used
for characterization is 26.23 dBm.
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