Reliable wireless connectivity is arguably the most important feature for IoT devices. When developing an IoT device, one or more antennas must be chosen for the device. With a large number of antennas available on the market, it’s easy to become overwhelmed by the amount of options.
This is a common challenge many of our customers have faced. With constraints spanning size, cost, performance, and application requirements, selecting the optimal antenna has become a very complex decision in IoT development.
This article will guide you through the process of selecting the best antenna solution for your product. To make things easier, we will approach the problem from the perspective of an example device. Our example device is battery-powered with LoRa connectivity and global satellite navigation via GNSS. The device features a plastic casing with metal sections and is designed to be portable. We will focus on choosing between off-the-shelf antennas and custom antenna design.
Example device
- Portable, battery-powered
- Plastic casing with metallic sections
- Antennas:
- 1x LoRa
- 1x GNSS
Decision between off-the-shelf vs. custom antenna design
In our earlier blog post, we discussed differences between off-the-shelf antennas and custom antenna design. Here, we will start the process of choosing an antenna from the perspective of different device categories. Here are three device categories that have major effects in the choice of antennas:
Indoor and outdoor fixed devices
- Little to no change in environment around antenna
- Less strict size limitations: easier to align with design rules
- No batteries: easier antenna integration
- Example product: IoT gateway, Wi-Fi access point
Recommended solution: off-the-shelf antenna
Portable devices, wearables
- Changing environment around antenna, multiple use cases
- Smaller device size: challenging for antenna integration
- Placement of battery and other components can affect antenna performance
- Antennas should be omnidirectional to work in all orientations
- Example product: IoT asset tracker, smartwatch
Recommended solutions: compact ceramic antenna, custom antenna design
Devices with metallic casing and other materials
- Metal surfaces can detune antenna and decrease total efficiency
- With custom antenna design, antenna performance can be equal or even better than without metal in the casing
- Other materials such as plastics must be considered in antenna design
- Example product: IoT industrial sensors, premium consumer devices with metal construction
Recommended solution: custom antenna design
Devices with fixed installation and relaxed size restraints are good fit for off-the-shelf antennas.
Selecting the optimal antenna step-by-step
Step 1 – Use case
Selecting the antenna for your product starts by determining its intended environment and use case. With our example device, we are operating in many different use cases, as portability means the device could be on a desk, inside a vehicle, on a charging dock or perhaps close to the human body. The device’s antennas should work in all these use cases, which must be considered in antenna tuning. This affects clearances for the antenna as well as the antenna tuning circuit. Due to the size constraints of the device and space requirements for LoRa antennas, custom antenna design should be considered for our example device.
Step 2 – Orientation
Because our device varies in orientation, directive antennas are not suitable as the resulting narrow beam will not always be properly aligned towards the intended direction. This is especially important with portable devices featuring satellite navigation where good coverage towards the sky is required. This rules out hemispherically receiving off-the-shelf GNSS patch antennas for portable devices and wearables. This does not exclude all off-the-shelf solutions: there are numerous off-the-shelf GNSS antennas which receive omnidirectionally. However, combined with the constrained size requirement, a custom GNSS antenna design is the recommended choice for our example device. Furthermore, designing one custom antenna for a device lowers the design effort for additional custom antennas.
Step 3 – Other components
In addition to the use cases, the components of the device itself affect the antenna. Devices with metallic surfaces are especially important to consider when choosing the antenna. This includes components like large displays, metallic sections on the casing, other PCBs near the antenna, and batteries. When clearances are sufficiently small, metallic surfaces close to the antenna affect its performance such as gain and efficiency. Custom antennas excel in this type of environment: with clever antenna design, the effect of metal surfaces can be mitigated, and in some cases, even used to provide benefits! Our device’s metallic case and portable form-factor further reinforce the choice to go for a custom antenna design.
Wearables like the tiny technology demonstrator Omnicora benefit from custom antennas.
Final words
In this blog post, we went through the process of choosing the best antenna option for an example device with LoRa and GNSS connectivity. Options were chosen based on the device’s form factor and use case.
The same process we presented here can be applied to your IoT device to choose the best antenna options for your scenario. However, small details can matter a lot!
If you are still unsure on how to proceed with your IoT device’s antennas, we are here to help. Radientum has expertise on numerous antenna technologies and types, and how to integrate them into real products with performance and cost-effectiveness in mind.
Antenna Designer
Sakari Sarkkinen
Sakari Sarkkinen is an Antenna Designer at Radientum with experience designing, integrating, and validating both custom and off-the-shelf antennas for wearables, industrial IoT devices, and medical applications. His background includes antenna simulation, prototype development, and hands-on laboratory testing and measurements.
Disclaimer: The views and opinions expressed in this article are those of the author. It is intended only as a sharing of antenna design knowledge for educational purposes.
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