If you have tested the nRF9151's GPS with the CMW100 or IQ station. We need to know:
1. What test waveform file is required?
2. Should we use the ARB file or the CW waveform?
If you have tested the nRF9151's GPS with the CMW100 or IQ station. We need to know:
1. What test waveform file is required?
2. Should we use the ARB file or the CW waveform?
Hi,
For full GNSS signaling CN0 test, you may use a GNSS ARB signal from a signal generator (conducted GNSS signaling mode, typically around -135 dBm), and read CN0 from the GNSS logs / UART traces as described in the documentation. And as in this case you requires a GNSS‑modulated signal, the testing should be done using an ARB GNSS waveform or a GNSS simulator rather than a CW tone.
Best Regards,
Syed Maysum
Hi,
Any recommended ARB files for GPS testing with the CMW100/CMW500?
Hi,
We are checking internally if there are any recommended reference ARB files for GPS testing and will get back to you shortly. Thank you for your patience.
Best Regards,
Syed Maysum
Hi,
R&S CMW systems typically include GNSS ARB files such as GPS_single.wv or GPS_default.wv, which are usually available under the CMW waveform directory (...\Rohde-Schwarz\CMW\Data\waveform\, depending on the device model and installation). These can be used for this purpose.
Best Regards,
Syed Maysum
Hi,
R&S CMW systems typically include GNSS ARB files such as GPS_single.wv or GPS_default.wv, which are usually available under the CMW waveform directory (...\Rohde-Schwarz\CMW\Data\waveform\, depending on the device model and installation). These can be used for this purpose.
Best Regards,
Syed Maysum
Hi,
I previously tried using the GPS_single.wv or GPS_default.wv waveform files on the CMW100 or CMW500 for conducted GPS L1 testing, but the CN0 values kept fluctuating, jumping between the original 40 and 0.
Hi,
CN0 intermittently dropping to 0 during conducted GNSS signaling tests typically indicates that the receiver temporarily loses tracking and then reacquires the signal. This is most often related to signal level or test setup calibration, rather than the ARB waveform itself. Please verify that the effective signal level at the nRF9151 GNSS input (including cable loss and any external LNA gain) is very low, typically around -135 dBm, and allow sufficient time for the receiver to reach stable tracking.
Additionally, please check the modem firmware version. With modem firmware v2.0.1, there is a known behavior where tracked satellite reporting can fluctuate after initial acquisition. Updating to modem firmware v2.0.2 or later is recommended, as it includes improvements to GNSS tracking stability and reporting.
Best Regards,
Syed Maysum
Hi,
Sorry for the late reply. For the NRF9151 test, the firmware version used was nrf91x1_2.0.2. The signal level generated by the test instrument was set to -130 dBm. Additionally, the external LNA for the GNSS has a gain of 16 dB. A 50Ω cable was used to connect to the test port, with a 1 dB compensation for line loss. However, during testing, the CN0 value still exhibited fluctuations/jumping. Attached is the log file of the CN0 test results.
Hi,
No problem, thanks for sharing the setup details. Based on the numbers you provided, the effective signal level at the nRF9151 GNSS input comes out to around –115 dBm (–130 dBm generator + 16 dB LNA – 1 dB cable loss). This is quite a bit stronger than what a GNSS receiver normally expects.
For conducted GNSS signaling CN0 tests, the recommended level at the GNSS input is typically around –135 dBm, and this already assumes that an external GNSS LNA is present. If the signal is much stronger than this, the receiver can temporarily lose tracking, which would show up as CN0 fluctuations. We suggest lowering the effective signal level at the GNSS input (for example by reducing the generator output, or temporarily bypassing the external LNA) so that it is closer to –135 dBm, and then re-running the test.
Best Regards,
Syed Maysum
Hi,
I don't think dBm and dB can be converted equivalently — their units are different. The actual power reaching the IC is still –130 dBm.