Solution
For the out-of-band measurement, the RBW filter type (Gaussian), the RBW filter BW, and the Bandwidth Integral used for each of the offset segments can be read from the offset segment settings for the configured Mask type. This is in compliance with the 3GPP standards.
For the in-band , RBW filter type is 'FFT based' which is why there are more variations in the spectrum plot.
VBW filter is not enabled in the LTE SEM measurement.
-------------------------------------------------------------------------------------------------------------------------------------------------------------
Question 1:
Is it possible to open code source in filter API for both in-band and out-band? So that customer can select filter by user case.
Answer 1:
In the LTE SEM, the sweep time is fixed to 1 ms (one subframe) as per the standard. The specs also specify using RBW filtering for the Offset segments. Both Sweep time and RBW BW settings can be honored only when the RBW filter type is not 'FFT based'. Gaussian is the filter of choice for the RBW filter for the offset segments.
-------------------------------------------------------------------------------------------------------------------------------------------------------------
Question 2:
Could I know why we use different filter type for in-band and out-band? The theory is?
Answer 2:
For the Carrier power measurement, specs do not recommend any RBW filter BW or the Filter type to be used for the measurement. Therefore, the RBW filter BW is auto computed by setting the RBW filter type to 'FFT based'.
Workaround:
The RFmxSpecAn SEM measurement has the option to set the RBW filter type and RBW filter BW for Carrier as well. But the SEM offset segment settings have to be individually configured for the mask-type of interest. The customer can use RFmxSpecAn SEM measurement instead of RFmxLTE SEM.