White Paper: Options of Integrating Antennas into IOT Wireless Embedded Devices
- compositor09
- May 28
- 5 min read
When designing wireless devices, it is essential to pay close attention to the antenna layout on the PCB. Factors such as space, positioning, clearance, ground plane, and proper connection with other components on the PCB all affect antenna performance. Considering these aspects correctly from the initial design concept will help ensure successful transmission and reliable wireless performance.
An antenna that performs well in free space, as listed in the supplier’s datasheet, may behave differently when installed in a real device. In the worst-case scenario, if the antenna is squeezed into a space near the end of the design phase without considering the manufacturer's intended layout guidelines, the performance can be poor. This often leads to design modifications, increasing costs and delaying time-to-market. By following the five fundamental principles below for designing embedded antennas in electronic devices, it’s more likely to ensure first-time design success.
Antenna Placement
Considering that the antennas are highly sensitive to their surrounding environment, their approximate location within the device can significantly impact the design. Please place the antenna in a position where it is protected from objects that could cause electrical interference.
Metal objects near the antenna can affect its performance. Take a bicycle tracker as an example—the tracker may be mounted on the bike’s metal frame. When the device is used in close proximity to metal objects, the antenna should be positioned as far away from the metal structure as possible. This allows the antenna to radiate without interference from the metal surroundings.
The device enclosure can impact antenna performance. If the enclosure is made of metal or glass-fiber-reinforced plastic, it can suppress the antenna’s radiation energy. Unless you're using a specially designed antenna, it's best to consider using non-glass-fiber-filled plastic for the enclosure to ensure optimal performance.
The antenna's position on the PCB affects RF performance. Since the antenna needs to radiate in six directions, placement is critical. While antennas are often designed to work best at the corners of the PCB, some perform better along the long or short edge. You are free to adjust the exact location, but be sure to carefully read the manufacturer's datasheet and follow the recommended placement. This ensures proper radiation and optimal performance.
Antenna Position Relative to Other Components
Even a high-performance, high-efficiency antenna will not function properly if it is placed too close to components that cause interference. This interference may come from specific elements on the PCB or from nearby objects around the antenna.
Certain components can interfere with the signals radiated by the antenna. Batteries, LCDs, motors, and other metallic objects may generate noise or reflections that degrade antenna performance. Therefore, the antenna should be placed as far away from these objects as possible.
Figure 1 illustrates the antenna’s keep-out area and the gap extending through all layers of the PCB.
Other nearby antennas can also cause issues, especially if they operate at similar frequencies or at frequencies that resonate with the primary wavelength. These nearby antennas can cause detuning of the main antenna. Ideally, antennas should be isolated from each other—for example, with a maximum isolation of -10 dB at 1 GHz and -20 dB at 2 GHz.
Antennas may also require a keep-out area. In this region, only the antenna solder pads and the feed connection are present, allowing the antenna to operate properly in free space. Refer to the datasheet for the manufacturer's specified clearance dimensions and measurements. The keep-out area is often slightly larger than the physical antenna itself, and clearance may be required across all PCB layers. Design your PCB based on the recommended antenna size and clearance specifications.
Check Ground Plane Length Requirements
Surface-mount device (SMD) antennas typically require a ground plane to radiate energy effectively. The ground plane acts like a mirror, helping to balance the antenna’s reciprocity.
The ground plane is usually longer than the antenna, and its length depends on the lowest operating frequency. The datasheet will specify the ground plane requirements, which means you need to leave a keep-out area beneath the antenna. If space is limited, we recommend choosing an antenna that requires a very small ground plane while still meeting the efficiency standards for over-the-air radiation.
Figure 2 shows that the ground plane can be adjacent to the antenna, located underneath it, or both.
The distance between the antenna and the ground plane is also crucial and should comply with the specifications in the MIOT’s datasheet. Since each antenna is different, ground plane requirements can be a decisive factor in antenna selection.
The feed line connects the antenna to the radio. A poorly designed transmission line can reduce antenna performance by up to 50%. This part of the design requires special attention.
Two important design principles:
Place the RF circuitry close to the antenna to minimize transmission loss. A well-designed transmission line with evenly spaced edge vias helps reduce noise and signal loss, which can otherwise degrade antenna performance.
Remember to consider all layers in the PCB stack-up; avoid placing traces directly above or below the antenna. All transmission lines should be designed with a characteristic impedance of 50 Ω.
Consider Alternative Antenna
Surface-mount device (SMD) antennas are very useful in designs due to their small footprint, but there are other options available. Antennas in the form of flexible printed circuits (FPC) can provide valuable design alternatives in certain cases.
Figure 3 shows examples of both SMD and FPC antennas Designed & Made by MIOT.
FPC antennas connect to the circuit via their built-in RF coaxial cable and offer various connection options. They can be used in different locations within the device without occupying any valuable PCB space. FPC antennas can be bent or folded, providing multiple placement possibilities—for example, they can be mounted inside the device enclosure.
Another key advantage of FPC antennas is that they do not require a ground plane, which simplifies integration. However, the coaxial cable becomes part of the antenna, so careful routing of the cable is necessary. We recommend keeping this portion of the antenna away from other components that may generate noise or interference.
FPC antennas offer some practical benefits, but the final choice between FPC and SMD antennas depends on the device’s nature, manufacturing process, and production volume. FPC antennas are fixed in place with adhesives and require manual placement, making them suitable for small-batch production, shorter lead times, and manual assembly. On the other hand, SMD antennas can be placed on the PCB using pick-and-place machines. For devices requiring large-scale production to reduce labor costs, SMD antennas are the better choice.
Conclusion
Generally, using low-profile, high-performance antennas will make your design process easier. However, RF design is very complex, so it is advisable to consult an RF expert before finalizing your design. In most cases, the design will be tested in an anechoic chamber to verify its performance and check for unwanted emissions.
About MIOT
MIOT empowers innovators to Design. Connect. Thrive.
We help businesses accelerate their journey into the Internet of Things (IoT) by removing technical barriers and simplifying wireless integration. MIOT designs and supplies a wide range of RF components, including antennas, RF cables, enclosures, PCB assemblies, and accessories—backed by expert engineering and flexible customization options.
Support and Services
Beyond hardware, MIOT offers a wide range of support and custom services to ensure your project's success:
Complimentary antenna matching and selection support
Custom cable assemblies and RF connector solutions
ODM and EMS support for IoT hardware
Antenna tuning and optimization for your device
Design consulting and technical guidance from concept to deployment
Contact Information
Email: info@miotsolutions.com