The set command measures Signal-to-Noise Ratio (SNR).
To measure SNR correctly, the Carrier Wave (CW) offset must be +330 kHz for
the LTE-M and DECT NR+ modes and
+45 kHz for the Narrowband Internet of Things (NB-IoT) mode.
Syntax:
%XRFTEST=<test>,<operation>,<param0>,<param1>,…,<param4>
The set command parameters and their defined values are the following:
- <test>
- 3 – RX SNR.
- <operation>
- 1 – ON.
Note: OFF <operation> is not
needed due to automatic stop.
- <param0>
- 3GPP band number. Use 24 for Global Navigation Satellite System (GNSS) reception.
- DECT NR+ bands 1, 2, 9, and 22 are supported
when <param3> is 10. See ETSI TS 103 636-2
V1.4.1 Table 5.2-1.
- <param1>
- Valid range 6000–22000 (corresponds to 600.0 MHz–2200.0 MHz).
- In DECT NR+, the valid range is 18800–19300 (corresponds to 1880.0
MHz–1930.0 MHz) depending on the DECT NR+ band selected in
<param0>.
- <param2>
- RX signal power at the SiP antenna port.
- Valid range from −127 dBm to −25 dBm.
- <param3>
- System mode.
- 0 – NB-IoT.
- 1 – LTE-M.
- 10 – DECT NR+.
- <param4>
- Enabling AFC correction during SNR test.
1 – Enable.
0 – Disable.
If
<param4> is not given, AFC correction is disabled.
Response syntax:
%XRFTEST: <snr>,<antenna_power>,<sb2hnbr>,<headroom>
The response parameters and their defined values are the following:
- <snr>
- Result of the SNR measurement in q4 dB. q4 means that dividing the result by
24 = 16 dB.
- The SNR calculation is done by computing the power of the signal bins
and dividing it by the power of all the other bins.
- <antenna_power>
- Measured signal power at the System in Package (SiP) antenna port in q8 dBm.
q8 means dividing the result by 28 = 256 gives dBm.
- <sb2hnbr>
- Signal bin to highest noise bin ratio in q4 dB.
- Computed by dividing the signal bin by the power of the highest noise bin.
- Allows to find spurious signals possibly affecting reception. The expected value is
the same or higher than <snr>.
- <headroom>
- Time domain signal headroom in dBFullScale.
- Expected value is −15 dBFS or −16 dBFS if the signal level in generator corresponds to
the level given in <param2>.
The following command example enables the RX SNR measurement and RF receiver for Band 1,
2140.0 MHz, −65 dBm, LTE-M mode, AFC correction enabled:
AT%XRFTEST=3,1,1,21400,-65,1,1
%XRFTEST: 496,-17002,598,-16
OK
Note: 496/16 = 31 dB. −17002/256 = −66.4 dBm. 598/16=37.3 dB.