Achieving reliable multiband RF in a sealed outdoor gateway

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metraTec designed and manufactured the BeeBase gateway for the HoneyLink project. It is the hub of a professional beehive monitoring system, aggregating data from up to 64 wireless hive scales and sending it to the cloud over LTE Cat-M/NB-IoT.The gateway is installed outdoors, solar-powered, rated IP65, and fully encapsulated in epoxy resin for long-term field durability.

That encapsulation created the RF risk. Epoxy changes the dielectric environment around the PCB and antenna after the design is cast, shifting the antenna’s tuned response and, on the LTE Cat-M/NB-IoT path, potentially moving multiband operation out of range. metraTec also had to fit three RF functions, LTE Cat-M/NB-IoT, GPS, and 2.4 GHz, on one compact PCB and keep them from interfering.

metraTec evaluated surface-mount PCB, flexible printed-circuit, and ceramic patch antennas, then selected the RUN mXTEND™ on recovery margin after encapsulation. As part of Ignion’s Virtual Antenna® technology family, the RUN mXTEND™ uses a non-resonant booster with a tunable matching network and the PCB ground plane as the radiating structure. Because it does not rely on a fixed pre-tuned resonance, the matching network could recover and retune the LTE response after resin casting rather than lock in a detuned build.

Each RF function has its own RUN mXTEND™ implementation and matching network, tuned as a complete system inside the final encapsulated build. Coexistence was handled explicitly: the modem time-multiplexes LTE and GPS, the 2.4 GHz booster sits on the opposite side of the PCB from the LTE path, and a SAW bandpass filter adds more than 30 dB attenuation of nearby LTE transmit signals to protect the 2.4 GHz receiver.

• Return loss recovered to S11 less than or equal to −10 dB across the LTE Cat-M/NB-IoT and 2.4 GHz ranges in the final epoxy-encapsulated build
• Three RF functions (LTE Cat-M/NB-IoT, GPS, 2.4 GHz) coexisting on a single compact PCB
• RF validated in the real mechanical configuration, an outdoor solar-powered sealed gateway, not an open development board
• First production batch shipping from Germany since October 2025, with European expansion planned