v1.0

Non-signaling mode

In the non-signaling mode, either continuous TX or RX mode is used.

In the non-signaling mode, closed-loop power control is not active which may cause TX power to drift. Drift may happen with long TX transmissions using over 10 dBm power levels. The RF tester must be set to 1.4 MHz BW to decode non-signaling mode TX signal.

The non-signaling RX mode uses Carrier Wave (CW) signal for Signal-to-Noise Ratio (SNR) measurement and returns SNR and RSSI values for each measured frequency point.

The non-signaling mode SNR result can be converted to approximate sensitivity with the following formula:

Sensitivity [dBm] = Prx_snr [dBm] + BB_snr [dB] - SNR_result [dB]

where

Prx_snr
CW level from signal generator [dBm]. The power level should be -90 dBm or less at the antenna feed pad.
BB_snr
Required minimum SNR to reach 5% block error rate (BLER). For Cat-M1, 0.5 dB can be used, and for Cat-NB1, 1.5 dB can be used.
SNR_result
SNR measurement result [dB]

In the non-signaling mode, an RSSI scan test can be used to detect if noise from other sources, such as Integrated Circuit (IC)s or LEDs, is coupling to the LTE antenna RF path on the Printed Circuit Board (PCB). The test is a similar sweep as a non-signaling receiver sensitivity SNR test but without a CW test signal from an external signal generator. The level of the test signal in the XRFTEST AT command should be set to -90 dBm to set the RX gain properly. The expected measured SNR variation is less than 2 dB. The test may also reveal noise that originates from some other source than the Device Under Test (DUT), for example, an LTE base station nearby.

The XRFTEST parameters used in the non-signaling mode tests are defined in RF test execution %XRFTEST in nRF91 AT Commands Reference Guide.