The %XRFTEST AT command with the GPS SNR ON parameters starts a Global Positioning System (GPS) Signal-to-Noise Ratio (SNR) test. The test expects the Carrier Wave (CW) in the signal generator to be at 1575.750 MHz, which means a 330 kHz offset from the GPS center frequency of 1575.42 MHz. The duration of the measurement is 1 ms.
The test is automatically disabled when it is finished. The %XRFTEST AT command with the GPS SNR OFF parameters is not needed.
The recommended signal level for GPS testing is -90 dBm. The expected SNR with this signal level is normally more than 12 dB.
The following command example executes a GPS SNR test:
%XRFTEST=2,1,0
%XRFTEST: 514, -27392 // Result: SNR 514/16 = 32.125dB, RSSI -27392/256 = -107dBm
OK
The GPS functionality test has one input parameter that is described in the following table:
Parameter name | Parameter description | Range | Value description |
---|---|---|---|
<param0> | Signal level at antenna | -127 to -25 | Signal generator level at antenna [dBm] |
nRF9160 responds to the GPS SNR ON parameters of the %XRFTEST AT command with the measured GPS SNR and RSSI values. The SNR is given in the q4 (dB) format. Dividing the result by 24 = 16 gives the dB value of the antenna power.
The RSSI signal level at the antenna is given in the q8 (dBm) format. Dividing the result by 28 =256 gives the dBm value of the RSSI.
For more information on GPS testing with the %XRFTEST AT command, see GPS SNR testing in nRF91 AT Commands Reference Guide.