Rohde&Schwarz R&S®NRQ6 ACLR 100 MHz (Using FFT Filtering) - Application Sheet Application Sheet
R&S®NRQ6
ACLR 100 MHz (Using FFT Filtering)
Application Sheet
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1178828802
Version 03
R&S®NRQ6
Your Task
1 Your Task
This application sheet describes how to perform ACLR measurements on LTE
Advanced/5G signals with a bandwidth of 100 MHz.
The R&S NRQ6 frequency selective power sensor has a built-in solution for ACLR
measurements, but this function is limited to 20 MHz LTE signals. The limitation is due
to the maximum instantaneous bandwidth of 100 MHz total for five channels.
The obvious alternative way would be to replace the ACLR measurement by several
separate power measurements at the five frequencies, using the 100 MHz flat filter.
Unfortunately, the stopband bandwidth of the 100 MHz flat filter is 160 MHz, due to
limited number of FIR coefficients at this high sampling rate. Thus, you would see
strong cross-talk of the main channel in the adjacent channels.
This application sheet describes a way to use FFT filtering to realize very steep filters
needed for LTE advanced/5G ACLR measurements.
2 Possible Solution
The R&S NRQ6 has some built-in features to perform simple spectral analysis of the
I/Q samples. The R&S NRQ6-K1 I/Q data interface option is not required.
These features are accessible by SCPI using the SENS:TRAC:IQ:FFT:… node.
Beside the magnitude spectrum displayed with "Signal Check" of the web user interface, the following command measures the power within a dedicated bandwidth by
adding up the power in the frequency domain:
SENS:TRAC:IQ:FFT:SPEC:ABS:SUM?
Without additional parameter, this function calculates the power over the whole set resolution bandwidth.
Adding a numerical parameter reduces the spectral bandwidth considered.
If the command returns NaN, the FFT buffer is too large to be processed. Reduce the
number of requested I/Q samples to obtain a result.
Example:
Resolution bandwidth is set to 100 MHz.
SENS:TRAC:IQ:FFT:SPEC:ABS:SUM? -> The power between -50 MHz and
+50 MHz around the carrier frequency is measured.
SENS:TRAC:IQ:FFT:SPEC:ABS:SUM? 0.9 -> The power between -45 MHz and
+45 MHz around the carrier frequency is measured.
2Application Sheet 1178.8288.02 ─ 03
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