In our previous blog, we put our CYW20829 MCU to the test and achieved 2.3 km of Bluetooth® Low Energy (LE) connectivity. We felt compelled to improve upon our previous range, so we returned to repeat our testing. This time, our goal was to maintain our Bluetooth® LE Long Range connection between Newport Beach Pier and Balboa Pier—a whopping 2.8 km. We first optimized the timing of our Bluetooth ® LE connection and easily achieved 2.8 km of connected range.
Then, we added a custom front-end module to improve our link budget, and improved our range to over 5.7 km. All the way from Newport Beach Pier to the heart of Huntington Beach. When we first achieved 2.3 km of Bluetooth® LE Long Range connectivity, each CYW20829 board was configured with an internal 10 dBm TX power amplifier (iPA) and an internal low noise amplifier (iLNA) to achieve up to -106 dBm of RX sensitivity, for a link budget of up to 116 dB.
These amplifiers are internal to our CYW20829 MCU—the iPA amplifies the transmitted signal, while the iLNA amplifies the received signal. With this solution, we went back to Newport Beach and improved our line-of-sight, or LoS, connection range to 2.8 km and the reconnection range to 2.7 km as a result of timing optimization.
To achieve nearly 6 km of Bluetooth® LE Long Range connectivity, we used the Berex 8TR8219 external front-end module, or external FEM, along with our CYW20829 MCU, as shown in Figure 1.
Berex customized the 8TR8219 for us to optimize the range performance of the CYW20829 MCU, namely through power saving.
The Berex 8TR8219 is both an external power amplifier (ePA) and external low noise amplifier (eLNA), so it amplifies both the transmitted signal and the received signal.
This solution further amplifies the RF signals from the CYW20829 MCU, for up to 12 dBm¹ of output power and up to -110 dBm of receiver sensitivity as shown in Figure 3.
As shown in Table 1, with a CYW20829 MCU chip-out Coded PHY (S8) sensitivity of up to -106 dBm and transmit output power of up to 10 dBm, we achieved a link budget of up to 116 dB.
With the Berex 8TR8219, we improved the Coded PHY (S8) sensitivity to -110 dBm and the transmit output power to 12 dBm, for a link budget of around 122 dB.
An increase in link budget of up to 6 dB using this CYW20829 MCU + FEM solution, we can see drastically improved Bluetooth® LE Long Range in an open environment.
With the CYW20829 MCU+FEM solution, we were able to easily connect at 2.8 km, between Newport Beach Pier and Balboa Pier, where we ran out of space for an LoS connection.
We tested again from Newport Beach Pier northwards into Huntington Beach with the CYW20829 MCU + FEM solution and achieved an LoS connection range of 5.7 km and a reconnection range of around 5.3 km.
As mentioned in the previous blog, we were far from testing in a perfect environment. There were plenty of sources of interference, including from bystanders with multiple 2.4 GHz devices and retail access points.
Certain applications require higher link budgets than our iPA/iLNA solution can provide. For example, warehouse environments frequently involve significant sources of interference from metal shelving and palletized goods. Environments with lots of inherent interference may require the higher link budget that an external FEM solution provides. In theory, every 6 dB of increased link budget doubles the range of a connection. We won’t see double the range in a noisy environment like a warehouse, but we can expect to see improved range.
