GNSS SNR test %XRFTEST set command

The set command executes a Global Navigation Satellite System (GNSS) Signal-to-Noise Ratio (SNR) test.

GNSS L1 frequency is 1575.42 MHz. This test expects the Carrier Wave (CW) in the signal generator to be 1575.750 MHz, which means that the offset is 330 kHz. The measurement duration is 1 ms.

Syntax:

%XRFTEST=<test>,<operation>,<param0>,<param1>,<param2>

The set command parameters and their defined values are the following:

<test>: 2 – GNSS SNR
<operation>: 1 – ON
Note: OFF <operation> is not needed due to automatic stop.
<param0>: RX signal power at the System in Package (SiP) GNSS port; Valid range from −127 dBm to −25 dBm or 0 = default gain −105 dBm

<param1>: AFC correction; 1 – Enable AFC correction in measurement; 0 – Disable AFC correction in measurement
<param2>: Frequency. Manually give RF frequency for nRF91x1 in 100 kHz format. Accepted value is +/- 10 MHz from the default GNSS frequency of 1575.42 MHz. Set the signal generator to f = <param2> + 330 kHz.
Note: If <param2> is not given, nRF91x1 uses the default GNSS L1 frequency 1575.42 MHz.

Note: It is recommended to set the signal level defined in the GNSS SNR ON parameters to the expected signal level at the GNSS antenna port of the nRF91x1 SiP.

Response syntax:

%XRFTEST: <snr>,<antenna_power>,<sb2hnbr>,<headroom>

The response parameters and their defined values are the following:

<snr>: The result of the SNR measurement in q4 dB. q4 means that dividing the result by 2⁴ = 16 gives dB.
<antenna_power>: Measured signal power at the SiP GNSS port in q8 dBm. q8 means that 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 executes a GNSS SNR test at –80 dBm level with AFC disabled:

AT%XRFTEST=2,1,-80,0
%XRFTEST: 364,-20506,455,-16
OK

Note: 364/16=22.75dB. –20506/256=–80.1dBm. 455/16 = 28.4dB.

The following command example executes an GNSS SNR test for –80 dBm. AFC correction is enabled and uses the result of the previous AFC measurement or AFC set. Instead of the default, the receiver frequency is set to 1575.0 MHz:

AT%XRFTEST=2,1,-80,1,15750
%XRFTEST: 364,-20506,455,-16
OK

Set command