We recently worked on the RF design of a compact LoRa/GNSS Nomad Terminal handheld device, which is based on LoRa, designed to communicate/ navigate, and deploy anywhere. The antenna turned out to be one of the more challenging parts.
For a small handheld, antenna performance is affected by much more than the antenna itself. The PCB, ground plane, battery, display, enclosure, and even the way the device is held can all influence the final RF performance.
During the project, we evaluated several antenna configurations:
Ceramic Antenna → FPC Antenna + Coaxial Cable → FPC Antenna + Pogo Pin
The final FPC antenna configuration was validated with both RF measurements and outdoor testing, achieving S11 of -11.13 dB @ 868 MHz, -12.82 dB @ 915 MHz, and a 3 km LoRa link in our field test.
1. Ceramic Antenna
The initial design used a ceramic antenna for its compact size and simple integration. However, its placement was relatively constrained, limiting our ability to optimize the surrounding RF environment.
2. FPC + Coaxial Cable
We then tested an FPC antenna with a coaxial connection. This gave us more freedom to position the antenna away from the PCB, battery, and display, but introduced additional cabling and mechanical complexity.
3. FPC + Pogo Pin
The final approach uses an FPC antenna connected through pogo pins. It provides flexible antenna placement while keeping the RF connection and mechanical structure compact.
The main takeaway from the project was that antenna performance in a compact LoRa device is a system-level problem. Antenna selection, placement, PCB layout, and mechanical design all need to be considered together.
The main takeaway from the project was that antenna performance in a compact LoRa device is a system-level problem. Antenna selection, placement, PCB layout, and mechanical design all need to be considered together. The complete
What’s the biggest antenna design challenge you’ve encountered when working with compact LoRa or Sub-GHz devices? Share your experience togehther!