The range and link robustness of Nordic nRF52 and nRF53 Series SoCs fulfill the requirements of most applications and use-cases, but sometimes adding an RF front end module (FEM) is the correct choice. An RF FEM increases the range at which two wireless devices can communicate, while also enhancing link robustness. Combining our nRF21540 RF FEM with an nRF52 or nRF53 Series SoC can boost range by up to a factor of 8.

In the image above, a regular connection with 0 dBm TX output power is compared to a +20 dBm TX output power connection with an nRF21540 RF FEM on both sides. Both the increased TX output power, as well as RX sensitivity improvements from the nRF21540 help boost the range of the connection.

Both the TX output power and the receiver sensitivity directly influence the link budget of a connection.

After the Bluetooth 5 specification increased the maximum permissible output power to +20 dBm, device output power is now limited by regulatory boundaries in most regions.

Pairing the nRF21540 RF FEM with an nRF52 or nRF53 Series SoC enables fine-grained TX power tunability, resulting in a TX power at maximum 1 dBm below the regulatory limits mentioned below. The TX gain is dynamically adjustable, enabling the possibility of implementing adaptive gain control algorithms. When running 1 Mbps Bluetooth LE, the RX sensitivity improves to -100 dBm for all nRF52 and nRF53 Series SoCs. The sensitivity is even better when running Bluetooth 5 Long Range, Thread or Zigbee.

The table below summarizes main regulatory output power limits in dBm, unless specified in Watts. Please check the rules for the region you plan to ship your product into.

In addition to increasing range, an RF FEM also increases the robustness of the link connection. A more robust link leads to less packet loss, meaning less retransmissions. Retransmissions are redundant packets that reduce energy efficiency and maximum throughput. The probability of successfully receiving the first packet also increases, resulting in a more stable link latency.

Many applications can benefit from adding an RF FEM, including asset tracking, smart home, industrial, smart agriculture, audio, as well as professional lighting. Smart home, as well as industrial applications, benefit from extended range (e.g. range in an entire home). Audio applications benefit via increased throughput and decreased latency.

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