nRF9151 is designed for 50 Ω load and does not have a mechanism to actively detect mismatch conditions. Typically, nRF9151 meets 3GPP specifications at up to a Voltage Standing Wave Ratio (VSWR) of 3:1 mismatch load. nRF9151 remains functional at up to a VSWR 5:1 mismatch load, but these conditions might shorten the device's lifetime. nRF9151 has been tested to withstand a momentary VSWR load of up to 10:1 without permanent damage.
For more information, see electrical specifications in the nRF9151 Product Specification.
Transmitter performance is expected to deteriorate under mismatch conditions. The effects include reduced maximum output power and accuracy, increased Error Vector Magnitude (EVM), worse linearity, and higher current consumption.
The following section shows the range of performance variation for a load VSWR of 3:1. The maximum TX output power inaccuracy of the transmitter increases about 1.5 dB at 1GHz and about 2 dB at 2 GHz in VSWR 3:1 mismatch compared to a 50 Ω load. The transmitter EVM increases from the typical <5% at 50 Ω to around 10% for QPSK and up to 12% for 16-QAM modulation.
The following figure shows nRF9151 TX performance for Cat-M1 at a VSWR of 3:1, 5 MHz bandwidth, QPSK modulation, and one resource block (RB), at a target power of 23 dBm.
The following figure shows nRF9151 TX EVM for Cat-M1 at a VSWR of 3:1, 5 MHz bandwidth, QPSK modulation, and one resource block, at a target power of 22 dBm.
The following figure shows nRF9151 TX EVM for Cat-M1 at a VSWR of 3:1, 5 MHz bandwidth, 16-QAM modulation, and one resource block, at a target power of 23 dBm.
The following figure shows nRF9151 TX Adjacent Channel Leakage Ratio (ACLR) for Cat-M1 at a VSWR of 3:1, 5 MHz bandwidth, QPSK modulation, and six RB, at the maximum target power. This corresponds to 22 dBm with MPR applied.