Wireless

2.4GHz FEM extends range and battery life

6th August 2020
Mick Elliott

The 2.4GHz RF front end module (FEM) nRF21540 from Nordic Semiconductor is a "plug and play" range extender that improves range and connection robustness, when combined with the multiprotocol wireless SoCs of nRF52 and nRF53 Series or other radios.

It requires just a minimal amount of external components.

The nRF21540 is available at Rutronik UK.

Thanks to the integrated power amplifier for output and the low noise amplifier for input (PA/LNA) the FEM enhances the link robustness of the low power short-range wireless solutions from Nordic.

When combined with an nRF52 Series SoC, the output power is +21dBm, the RX gain 13dB and the low noise figure 2.5dB. Thus, there is a superior link budget for up to 16x longer range. When combined with an nRF52840 SoC running Bluetooth Low Energy at 1 Mbps, for example, the nRF21540 improves the RX sensitivity by 5dBm to -100dBm. Coupled with the increased output power, the link budget is raised by 18dBm.

The nRF21540’s TX power is dynamically adjustable.

Its output power can be set in small increments. As the maximum output power exceeds the permissible value of the 2.4GHz band by 1dBm there is enough room to compensate losses in the signal chain to the antenna and at the same time take full advantage of the allowed 20dBm from antenna radiation.

This is the case for all protocols like Bluetooth, ZigBee, Thread, ANT and Gazell as well as proprietary variants.

If a radio connection is set up without the FEM in susceptible environments or close to the upper limit of the link budget of the wireless SoCs, the fault rate of the transmissions increases.

This leads to continuous retransmissions and thus to a higher energy consumption.

The nRF21540 reduces the number of attempts necessary to transmit the data packages, thus decreasing the energy balance of the application despite the additional energy needed by the range extender.

The device can operate across a -40°C to +105°C temperature range, allowing it to complement Nordic’s high temperature qualified nRF52833 and nRF5340 SoCs in industrial applications such as professional lighting.

Other target applications are asset tracking, remote controlled toys, drones, agricultural technology, audio and smart home use cases.

Nordic will roll out driver support for future releases of nRF5 SDK, nRF5 SDK for Thread and Zigbee, and the nRF Connect SDK to further enhance the ease of use with its SoCs.

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