LoRaWAN® Gateways: Radio Coexistence Issues and Solutions

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LoRa Alliance ® Whitepaper Page 44 of 49 LoRaWAN ® Gateways Radio Coexistence Issues and Solutions Copyright ©2021 LoRa Alliance, Inc. All rights reserved. www.lora-alliance.org 8 GATEWAY GNSS RECEIVER Like any other receiver of the LoRaWAN gateway, the GNSS receiver, when colocated with other emitters, can be desensitized due to: • Out-of-band spurious emissions generated by emitters falling in the GNSS band, causing desensitization of the GNSS gateway • High-power emitters acting as out-of-band blockers, causing desensitization of the LoRaWAN gateway Fortunately, GNSS antennas have a narrow bandwidth, which significantly increases the isolation with high-power emitters, such as LTE BS and DVB-T/T2 emitters. Separation distance then can be lowered but still must be considered. A typical GNSS radio architecture of a LoRaWAN gateway is presented here: GNSS receiver 1 2 3 4 Figure 29: GNSS front-end block diagram of LoRaWAN gateway A band-pass SAW filter (2) shall be inserted between the LNA (4) of the GNSS receiver (1) and the GNSS antenna port (3), ensuring excellent out-of-band blocker rejection. Usually, the LNA (4) and the band-pass filter (2) have very low maximum input power, such as +10dBm, for example. When colocated with high-power emitters, there is obviously a high risk of damage to the GNSS front end. Protecting the GNSS receiver with RF power limiters, for instance, is recommended. Issues may occur when adding an external active GNSS antenna due to potential linearity issues of the LNA or poor out-of-band rejection, causing desensitization of the GNSS receiver. The best architectures using GNSS antennas are therefore: • Passive antenna • Active antenna with SAW-LNA-SAW ( • Figure 30) or SAW-LNA architecture. The LNA gain shall be also minimized (15dB, for instance, instead of the usual 30dB) to optimize linearity performance. Other types of GNSS antenna are not recommended.

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