LoRaWAN® Gateways: Radio Coexistence Issues and Solutions

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LoRa Alliance ® Whitepaper Page 7 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org The spurious emissions may be of different kinds: • A continuous wave (CW) generated by a harmonic of an internal clock, for instance • A modulated signal generated by an external transmitter or a harmonic of an external transmitter • Noise (white or pink) generated by an external out-of-band high-power transmitter Figure 6: Out-of-band spurious emissions of transmitter For LoRaWAN gateways, the most critical transmitters regarding out-of-band noise generation are: • High-power TV transmitters • Cellular base stations operating in 3rd Generation Partnership Project (3GPP) bands close to the LoRaWAN unlicensed bands Any radio transmitter must meet out-of-band spurious emission specifications according to the local regulations. The specification depends on the application, the maximum radiated power (equivalent isotropically radiated power [EIRP]), the frequency range, etc. The specifications are intended to provide fair sharing of the spectrum and to avoid mutual interference between the different radio systems. However, when radio systems are colocated or sharing the same installation, the specifications may be not stringent enough. In this case, specific actions must be considered at the installation site. 2.6 TRANSMIT INTERMODULATION The transmit intermodulation performance is a measure of the capability of the transmitter to inhibit the generation of signals in its nonlinear elements caused by presence of the wanted signal and an interfering signal reaching the transmitter via the antenna. The intermodulation products (IP) are mainly generated by the single pole double throw (SPDT) and power amplifier (PA), as nonlinear components, in the presence of both the transmit (Tx) signal and reverse interfering signal.

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